In one or another of its compositions, concrete has been known and used since Roman times. Its use in Scottish church building, however, has been almost entirely confined to the period since the Second World War, catching up with its general use in nearly every other type of modern structure. Occasionally and especially in the Highlands, some older churches have been built using stone rubble in a concrete matrix.
In other simple and inexpensive buildings concrete blockwork has been used in place of brick and should be similarly maintained. Note that where the more porous breeze block forms an inner skin it will hold and retain water if allowed to get wet, requiring considerable time to dry out.
Concrete is made up of water, cement, gravel and sand in proportions depending on its role in the building and it can be finished in many ways, ranging from replicating the character of rough timber shuttering to a high degree of polish.
When reinforced by steelwork, normally in the form of rods or mesh, it can carry larger loads over greater distances and has been used structurally in this way in most of our modern concrete-built churches.
The most likely signs of concern will be cracking and spalling which is similar to the surface flaking of stonework, previously discussed. Spalling, however, is likely to prove more troublesome when it affects reinforced concrete, usually signifying that water has got through to the reinforcement underneath. This action will in turn have caused rusting and expansion of the metal, forcing off the thin concrete layer above. The whole process may have begun with the cracking of part of the concrete surface and might have been avoided by earlier and less expensive repair.
Remedying concrete faults needs special professional advice and you should first contact your appointed architect or surveyor if a regular general inspection is not imminent. See Professional Help module.
Glazing and Decorative Glass
STAINED GLASS is an almost universal feature of our churches. It is able to transform the experience of their interiors through the combined effect of light and colour while still conveying inspirational messages of faith in ways unique to this medium.
Several techniques have been developed to make stained glass. It can be self-coloured or comprised of plain material fused with coloured glass to give it lustre. It can be painted or stained with special pigments which bond with it and allow detail to be applied on top. Etching and surface-cutting give different effects while various surface textures are possible, refracting light in different ways.
TINTED GLASS is also commonly found, particularly in churches and chapels of the smaller reformed denominations.
Meanwhile PLAIN GLASS allows full natural light to enter and will make the interior less gloomy than if it was otherwise dominated by dark stained glass of questionable quality.
REPAIRS may be needed as a result, for instance, of vandalism or because time and weathering have affected the appearance of the glass or the strength of the framing which holds it together. This framework is traditionally formed in lead, as being soft enough to support the panes of glass without causing them to break through the metal expanding and contracting with change of temperature. Lead so used is inherently long-lasting – normally 100-150 years- and many lead-framed windows of lesser age have never needed much attention.
As such windows age, however, the H-shaped strips of lead known as cames can tend to lose some of their integrity, causing obvious buckling and bulging and threatening the safety of the whole window. If you notice signs of such trouble, ask an experienced glazier for advice. South-facing windows can be prone to this problem, particularly when solar heat builds up between protective secondary glazing and the main window. Always make sure that this gap is designed to include ventilation.
When any work affecting stained glass is contemplated you should always seek advice from an accredited practitioner in the art. Some will both repair windows and undertake new work while others are specialist restorers.
Repairs to windows made of plainer glass can be entrusted to less specialised glaziers with a good reputation for this type of work.
Larger windows are sometimes braced by iron rods which should not be allowed to rust.
Little maintenance is normally required.
Most leaded windows are made with small channels and weepholes at the base to collect condensation and remove it from the building. Keep them free of blockage. If it is necessary to clean the inside, ‘painted’ face of stained glass, use distilled water with cotton wool and certainly nothing chemical or abrasive.
PROTECTION from malicious damage is, however, a serious issue facing many congregations. Wire mesh grilles and polycarbonate or laminated glass sheeting, separately or in combination, are now recommended as the best means of protection.
Unless the vandalism extends to use of sticks and air guns, mesh grilles on their own should be adequate. They will be more easily maintained than glass or polycarbonate sheeting which can cause the overheating described above and may spoil the external view of the windows through reflection. Whichever method is used, the panels should be purpose-made to fit the size of each individual window, with no overlapping of stonework or other framing.
Fixings should always be non-ferrous to remove the risk of rust. Mesh guards will last longer if ordered as ‘powder coated’, preferably in black as hiding them best in daylight against the dark glazing behind.
You should be aware that much stained glass has high artistic value. Unless expertly advised otherwise, it should be treated as such and examined for its condition at least every 10 years.
All your pictorial stained glass should likewise be photographically recorded, in colour, to help its repair and restoration in case of damage.
For fuller advice on maintaining, protecting, repairing and replacing church window glass, a very useful reference is the Church of Scotland booklet Church Windows. See Window and Door Openings module.
The wood used in building and fitting out your church will have been chosen for two reasons:
1) Availability. It is unusual to find much carpentry and joinery in Scottish churches which has come from local woodland. As supplies of suitable building timber diminished during the Middle Ages and even earlier, imported softwood from the Baltic countries and, later, North America came into common use in Scotland. Scottish-grown hardwoods, such as oak, remained available in places but their use was not widespread. From the late 18th century, more exotic hardwoods were brought in, especially from Britain’s imperial possessions.
2) Fitness for Purpose. Structural timber must have inherent strength and be available in the sizes needed to bear the expected loads. As congregations grew in size during the 19th Century, many churches built first and foremost as ‘preaching houses’ required wider roof spans, uninterrupted by columns preventing direct sight of the pulpit. To achieve these spans with traditional structures and to bear the greater roof loads, more massive beams had to be specified, often from distant sources. Items subject to wear and tear, such as exposed flooring, doors and pews, need durable joinery while decorative woodwork is chosen to be attractive in colour and grain.
Wood is a living material subject in its natural state to eventual decay and disintegration. Prolonging its normal life cycle depends on understanding the strengths and weaknesses of different types of wood, how they react to their (unnatural) role in the built environment and how best to protect them from their three main enemies, rot, insect attack and fire.
A walk through woodland will reveal fallen trees and broken limbs gradually being eaten away by insects and by plant growths such as fungi. The same process will almost certainly take place in your building, given the presence of the following conditions:
1. Moisture. Rot relies firstly on dampness and humidity to form and spread. A bone-dry building will never suffer from rot. Scotland’s climate, however, hardly favours such dry conditions and the need to prevent water getting into the fabric has already been emphasised. (see Roofs and Walls).
2) Poor Ventilation. The growth of rot will be further encouraged where the vulnerable timber is boxed in, without access to moving air. Rot attack can be fended off by ensuring good ventilation and air circulation around woodwork enclosed and out of sight, such as under floor spaces and the internal linings of outside walls. Keep built-in vents free of blockage and do not remove or close off roof ventilators without providing another way of keeping air circulating in roof spaces.
3) Timber quality. Sapwood and poor quality timber will be the first to be affected by rot. The heartwood of most softwoods and many hardwoods can resist rot for some time.
4) Temperature. Given the encouragements of wet timber and lack of ventilation, rot may anyway be slow to take hold without the extra incentive of warm surroundings. Dry rot flourishes most at a temperature of 23 degrees centigrade but we should not forget that warmth is also necessary to combat damp.
Look out for two prevalent types of rot. Both take hold when fungal spores start to develop on damp timber which is also warm enough to give them opportunity to grow and spread.
1. Dry Rot which is only ‘dry’ in its final, most obvious form as a mushroom-like fruiting body, flourishes in moist, airless conditions, commonly in enclosed roof spaces, damp cellars, timber ‘safe’ lintels and behind wall panelling. It can be sensed through the typical ‘foosty’ smell it gives off when active and may be recognised by the cube-like disintegration of infected wood.
Given sufficient moisture sources, it will spread very quickly. Its spores and filaments can even travel across other materials, spreading the outbreak well beyond its original source.
It must be quickly dealt with, first by tracing and removing every possible source of moisture, by introducing effective ventilation and then examining the timbers closely to see how far they have been damaged. Where its strength and function has been affected the wood should be replaced with sound material. This will sometimes include cutting back rotten parts of structural beams and joists and splicing in new timber, adding steel or ply strengthening or patching with epoxy resin, all on the same principle followed by a dentist when filling and repairing a decayed tooth.
2. Wet Rot is usually more localised and requires higher levels of moisture than dry rot but it is still capable of causing considerable harm. It typically affects unpainted or poorly sealed joinery where water can gather unnoticed such as the sills and lower frames of windows. It is also common in timbers such as wallplates when in contact with wet masonry in under-ventilated spaces.
The cure is similar. After stopping the ingress of water, cut out and replace with new, well-seasoned wood. Note, however, that while the unaffected but still-damp remaining wood is drying out there remains the potential for dry rot taking over, as it prefers less moisture. Hence the absolute importance of maintaining proper ventilation.
Remember that fungal spores exist everywhere in the atmosphere but that they will never cause problems where the timber is dry and they can find no means of support. Only in damp conditions will they start to flourish.
1. Eliminate the cause of dampness immediately and allow the affected area to dry out as fast as possible
2. Ensure that all rotten timber is examined, replaced as necessary and that all infected material is safely destroyed.
In treating an outbreak, beware of allowing strong and toxic chemical products to be used on nearby woodwork. Any remaining rot spores and filaments will die away and be harmless in dry conditions. When treatment is recommended, effective ‘greener’ biochemical products are now available and these should be preferred.
We are luckily free from the ravages of timber-loving insects in tropical countries and even from the attentions of the Death Watch beetle which still seems to prefer a more southerly climate.
Woodworm is our most common insect predator. In its adult form it will bore its way into softer types of timber, inside which its larvae will grow and emerge having sucked out the wood’s natural humidity and made it brittle and useless. However woodworm, like rot, can only tolerate damp conditions and a dry, well-insulated building will not allow the larvae to survive.
If you spot the small circular holes which give away the presence of woodworm, do not automatically assume that it is still active. Previous careful inspections should have recognised obvious signs and may have recommended no action. It may be that the damage has only affected the outer layers of the more substantial pieces of timber, normally the sapwood, that the worm is now inactive and that the inner core is still sufficient for purpose. The strength of the timber should therefore be tested physically before deciding what should be replaced.
When it appears that it will be necessary to get rid of existing woodwork, do not assume that strong insecticide spraying is called for. Equally effective non-toxic biological methods of interfering with the insect’s life cycle are now available.
Regarding its effect on timber it is worth knowing that large beams and columns will withstand fire better over short periods than many other structural materials and that damage may be limited to charring of the outer rings, leaving the main core largely unaffected.
Timber does, however, burn and wooden panelling, lining, sarking, etc. is easily lost in a fire.
Roofs and Roof Drainage
Its ROOF is arguably the most important part of your church building. Keeping it in good condition, together with the gutters and downpipes, should be your first priority. Failure to do so will entail vastly more expense than undertaking quick and effective repair and could eventually threaten the future of the whole building.
Pitched Roofs feature on the great majority of Scottish churches built before the mid 20th Century. Slateis the usual finish, originally coming mainly from Scottish quarries but more recently sourced from Wales and the north-west of England. It comes in small units which need to be overlapped to keep out the rain and snow. To make economic use of varying sizes from the quarry it is often laid, to pleasing effect, in courses which diminish upwards towards the ridge.
Slates are drilled at the top or sides and then traditionally fixed by nails to underlying timber boarding (sarking). Failure of the nails can cause the slates to slip out of place (nailsickness). Where this is persistent and severe it will normally be necessary to remove and replace the slates over that entire roof slope. Sometimes the sarking will need replacing as well. In that case not all the slates will be capable of reuse and the rest will have to come from elsewhere, possibly taking matching replacements from a less conspicuous part of the roof.
The only Scottish slates now available will be second-hand and they are in short supply. An experienced slater, taking advice if necessary from a specialised architect or surveyor, should be able to obtain matching natural slate from these and other sources. Burlington slate from the north of England is often a good match.
Note that much imported slate is inferior in quality and life expectancy to that from British quarries. Obtain experienced advice before using it.
It is also important to ensure that non-rusting galvanised, stainless steel or copper nails are used in slating repair.
And never allow bitumen paint or other such ‘remedies’ to be applied to seal a nailsick roof. It will prevent the gentle natural ventilation needed by the structure below and make the slates incapable of reuse.
TILED ROOFS feature less frequently on Scottish churches.
Pantiles, traditionally used on older houses and farm buildings in the east of Scotland, have rarely been employed in church building. Plain pink Rosemary hand-made clay tiles, however, were specified by many church architects in the late 19th and earlier 20th Century and are still manufactured today. They are usually fixed with nails, like slates.
Concrete Tiles and other machine-made products will not normally make satisfactory substitutes for these traditional types. Apart from looking inferior they are likely to be considerably heavier and thus liable to overload and stress the structure below.
Whether your church roof is slated or tiled, however, you should always procure replacements as close as possible in colour, texture, thickness and size.
Some Scottish churches have been erected economically in prefabricated sections covered with this material. Dating from the later 19th and earlier 20th centuries, they mostly survive in remoter country areas. It is vulnerable to pitting and corrosion if left unpainted and to loosening of fixings and flashings. Keep it regularly painted, ensuring that the fixings are intact and that the flashing remains flush with the profile of the sheeting.
OTHER METAL FINISHES.
Lead Copper Zinc see FLAT ROOFS.
FLASHING describes the flexible material, usually metal, which is laid to prevent water from penetrating the joints between roof surfaces and upstanding features such as chimneys and skylights. Lead flashing comes in various thicknesses or codes. Code 5, being more flexible, is commonly used for this purpose with heavier grades being specified for other roofing work. Metal flashing is also carried out in Zinc and Copper.
Non-metallic flashings in mineral felt strips, pitch and artificial composite products will not be so durable. However all forms of flashing are prone to eventual failure by pitting or cracking and they can be displaced in severe weather. Inspect for security after storms and when any high level work is required. Flashband tape can safely be used for emergency repair and should be replaced by more permanent flashing within 6 months.
RIDGING is similar in purpose, comprising specially shaped tile or metal units protecting the apex of a pitched roof from water penetration. Being exposed, these ridges are also vulnerable to high winds and they should regularly be checked by eye for integrity. At the same time, make sure that the clips attaching metal ridging are all still in place.
UNDERLYING STRUCTURAL ELEMENTS normally comprise Roof Trusses, some simple, others more sophisticated, supporting lighter timber framing which in turn supports the ‘sarking’ mentioned above. In very simple buildings and in some where elaborately carved trusses are designed to enhance the church interior this structure may be exposed to view from below but more often it will be concealed above a ceiling.
The ends of the trusses will be seated on or near the wallheads, protected by the edges of the roof and the gutters, and so will be affected by any lack of proper maintenance. Wet or dry rot problems then commonly ensue with costly demands on fabric maintenance funds even if cured without long delay. Where truss ends rest on corbels, watch for drips caused by an unseen roof leak overhead. It is known for water to collect here and to start to rot the timber.
FLAT ROOFS suited to our climate are not laid strictly level, being designed to slope gently towards guttering or rainwater outlets. On older church buildings they will normally appear only as part of later extensions. From the mid-20th Century to the present day, however, they have become commonplace as part of the general changes in architectural practice and fashion dictated by new structural possibilities and the arrival of new materials.
ROOF FINISHES in higher quality work will be metallic – Lead, Zinc, Copper or Coated Steel.
Cheaper construction will rely on mineral felt, sometimes surfaced with stone chippings, or asphalt. These roof surfaces have shorter lives and are prone to cracking with age and where this combines with pools of water caused by faulty drainage, water will be bound to penetrate.
Do not expect continuous patching of felt to be worthwhile. Total renewal will be needed sooner rather than later and it may be worth considering replacement with a more durable material, only using a ‘breathable’ underlay. Metal roofs, notably those formed in lead, will expand and contract according to temperature. This will also vary with the length of sheet used between expansion joints. Metals that have suffered only local damage should only need the replacement of individual sheets.
Lead roofs, normally formed in the thicker grades, will last for generations but are nevertheless vulnerable to puncture, for example by heavy footwear. It is thus good practice to put down duckboards for use when necessary and to lay them also over wider lead gutters. Laid in longer sheets or on steeper slopes, lead may also have a shorter life.
A lead roof can be patched on the spot by ‘burning’ but cracks and leaks will usually mean that the time has come to renew it.
The life expectancy in years of these roof finishes is roughly as follows:
Mineral Felt 15
And always when you suspect that water may have penetrated a flat roof and arrange for the repair of the covering, ensure that the structure below is always checked for possible rot damage before the job is finished.
Further information can be found on these websites of the respective Manufacturers’ Associations.
GETTING RID OF THE RAIN
In early times many roofs were built with overhangs to let the rain drip straight to the ground. Today rainwater is collected and directed downwards via the familiar system of gutters and downpipes known collectively as rainwater goods.
Eaves Gutters consist of long sections of channelling attached by brackets to the building. Traditionally they are formed in cast iron, modern alternatives being aluminium or heavy duty plastic. Cast Iron left unpainted will rust over time but it is essentially a long-life material particularly sympathetic to the character of older buildings. It is vital to ensure that the joints between the gutter lengths remain well sealed, that the fixing brackets are rust-free and secure and that no slippage or blockage has affected the intended flow of water into the outlets.
Parapet or ”Secret’ gutters lie behind walls raised above the level of the eaves and thus are normally invisible from ground level.They do not rely on ready-made components and are usually made on site by forming a metal lining, typically of lead, over timber boarding. Faults will not necessarily be as obvious as those affecting eaves gutters which can be inspected from the ground, making regular checking all the more important to make sure that they are free of rubbish and any pooling of standing water. Most such gutters, however, have a visible overflow which, when dripping, will indicate any blockage.
This advice applies equally to Valley Gutters and any similar hard-to see metal lining found between adjoining roof pitches.
Gutter outlets must likewise remain completely clear and it is strongly recommended to fit them with stainless steel or other non-rusting ‘birdcage’ mesh to prevent debris blocking the pipework below.
The incline of every gutter must remain adequate, something not always possible to judge when dry. It is better, therefore, to check this during rain or by using a hose, at the same time ensuring that the stop ends beyond the outlet are in good condition.
DOWNPIPES complete the process of safely removing external water from the building fabric. They may be attached to the exterior or concealed internally, sometimes working as an integral part of a structural system of metal columns within the building. The transfer of water from the gutters is sometimes assisted by hopperheads of greater size which can be attractively ornamental and demand the same degree of maintenance.
Cast Iron is the best choice of material for long-term duty if painted regularly, including parts not readily visible. Cast Aluminium is also now in common use but can be affected by atmospheric pollution. It should also be painted as protection as well as to make its shiny surface less conspicuous.
Plastic fittings are to be avoided. Their permanence is untested and, particularly where your building has any historical merit, they are likely to be out of sympathy with the building’s character.
When inspecting external pipework, note the condition of the clips holding it back to the wall which should remain well painted and rust free.
It is not always easy to check behind pipework and a good tip is to use a hand mirror for this purpose.
Other useful advice: To test if an iron downpipe is clear, see if it rings true when struck. When a pipe which runs straight to ground is blocked and cannot be easily cleared, it is better to break a length and to replace it soon than to leave the problem to get worse.
Internal Downpipes are usually much more difficult to monitor and access and if it is possible to replace them with an external system this may be well worth considering.
As general advice, it is always best to check for leaky rainwater goods when it is raining hard and any drips and blockages will be most easily apparent. Overflowing gutters are an obvious sign of weakness as is water running down the outside of pipework or adjoining walls. Also look for possible signs of trouble when snow is melting fast.
At other times, signs of green or other dark staining and streaking on nearby parts of the fabric will surely indicate that rainwater is not escaping to the ground as intended, the most likely cause being some fault with the rainwater goods.
It is essential to walk around your building regularly, on the lookout for just such signs and to move fast in dealing with the trouble.
To follow advice about drainage at the foot of your building, go to the section on WALLS.
Your church walls, like the roof, must act as an efficient barrier against the elements and they need the same regular inspection and attention to good maintenance. They also work to support the full weight of the roof (unless the building is of framed construction) while enclosing and defining the inside space and providing security and privacy.
Before the mid-19th Century, when transport became easier and cheaper, they will generally have been built from the most suitable locally available material. If your church was built before the 1930s it will most likely be walled in stone or, unusually in Scotland, in brick, which is more often found in ancillary halls and other additions and extensions. From the 1940s, however, modern methods of construction in e.g. concrete and steel were often adopted for a new wave of church building, particularly in the New Towns and expanding suburbs, resulting in some different technical demands on their maintenance and repair.
Where a rendering has been applied it is usually to give added weather protection to exposed or less finely-built areas of masonry or to unify the appearance of a building which has a variety of surface finishes.
Brick walls may be solid or built with a cavity inside, separating the external and internal skins, as protection from moisture transmission and to improve insulation. Cavity walls can be distinguished from solid walls by the difference in bonding.
In stone and brick building the mortar joints bonding the masonry together were traditionally formed in the tried and tested mixture of slaked lime, sand and water. Portland cement has widely and mistakenly been used to replace the lime content in much stone repair work since the 1930’s with the consequences explained below.
The STONE mainly used in Scottish building was formed in one of two basic ways:
1) SEDIMENTARY comprising:
a) Sandstone which is made up of small particles of rock deposited in beds or layers and compressed over enormous lengths of time into solid form, its hardness depending on the degree of pressure and material composition.
2) IGNEOUS and METAMORPHIC, the result of volcanic activity, typically forming
a) Granite. This extremely hard and durable stone has been quarried particularly around Aberdeen and in parts of Dumfries-shire and Galloway. Nearly all our granite church buildings can be found in these two areas.
b) Whinstone, a dark-coloured material found mainly in Lanarkshire and the Borders, is a particularly hard and durable type of stone which does not readily fracture and spall.
c) Schist is a coarse-grained form of metamorphic rock found, for example, in the West Highlands, where churchbuilders have often used this easily-split material. It is unsuited for dressings and other carved stonework where it has normally been replaced by sandstone.
Limestone, another sedimentary type, has been little-used in Scotland as building stone and has mainly been exploited for its use as lime in mortars and harling and for agricultural purposes.
Scotland’s extensive deposits of SANDSTONE have ensured its constant use in church building and repair until, by the 1930’s, nearly all the quarries were exhausted or had became uneconomic for other reasons. Except for surviving sources mostly in Dumfriesshire (red sandstone) and in Moray (light buff), our sandstone is now supplied mainly from the north of England.
Blocks have traditionally been finished in a variety of ways depending on the quality of the stone and the available resources in money and skilled labour. They range from fine ashlar with almost invisible joints to coarse rubble fieldstone built uncoursed with small pinnings and with wider mortar joints.
see Roofs and Roof Drainage
Stone walls will normally have been built with fair faces to the outside and inside and with a rubble core in the centre.
The way the stone is laid is vitally important to its durability. Its original formation can be seen in the visible layering of each block and they should be laid in the same way with the ‘strata’ running horizontally across the stone.
When, by mistake, a block is laid with the layers running vertically from the front surface to the back or (worse) from side to side across the width, it will eventually split or flake away, sometimes helped by frost action. Such damage should not cause huge structural problems in a wall but it will be unsightly and can cause nearby stonework to decay due to extra pressure and water finding its way to the inner part of the wall.
When descaling such stonework use wooden tools and a stiff bristle brush, remembering to sweep up the debris.
If stone mullions or tracery have been affected in this way, more urgent repair will be called for to avoid possible major work to the whole window.
A well-trained stonemason will use the repair method best suited to the type of stone and degree of erosion. Where spalling is superficial it may be sufficient to brush back the loose material to a firm surface but if the problem goes deeper, indenting of matching replacement stone will be recommended. For durable repair of small detail, a plastic mortar composition including crushed stone or sand may be preferred but this should only be considered if specially mixed and applied by an experienced mason. Alternative, off-the-peg synthetic plastic compounds cannot be recommended. They will not be matched to the composition of the stone, can trap water in the same way as hard mortars and will have a short life when compared with other methods.
A sandstone wall effectively acts like a sponge, absorbing water that soaks into it and then allowing it to dry out naturally when the weather improves. Drying will of course take place more quickly where walls are exposed to sun and prevailing wind, with north-facing walls being prone to more continuous dampness. The thickness of the wall will normally cope perfectly well with this weathering cycle, often helped by the middle layer of looser stone which allows any excessive incoming moisture to drain away downwards.
Problems can occur, however, at the weakest points which are usually the mortar joints. Poorly maintained or made using hard mortar instead of a rich lime mortar, they will allow water to be drawn into otherwise sound walls and this can be especially severe when affected by driving rain. Cement-rich pointing will also slow down the natural drying of the wall, making it more vulnerable to further dampness and to frost action which has further potential to damage saturated masonry. Particularly vulnerable are the high-level joints at gable copes, chimneys and parapets which are likely to require more frequent repointing.
The building can also be affected by ground moisture rising from the base of the wall. This is prevented in modern construction by building – in a damp-proof barrier slightly above ground level. Older churches, however, may need to rely on natural drying out and there will normally be nothing to worry about if:
1) the drainage around the church is working efficiently,
2) the ground level has not recently changed significantly
3) nothing has been heaped or piled up against the wall which could trap moisture behind.
There may be underbuilding – a low space between the floor of your church and the natural ground which is also intended to keep the floor free from rising damp and found in all but the oldest buildings. It will be ventilated by small horizontal openings near the base of the wall, fitted with grilles to keep out vermin and any debris that might blow in accidentally. It is important to keep these vents in good condition and to check regularly if there is any obstruction to the free flow of air.
When a masonry wall or part of it has been allowed to become thoroughly saturated, any timber close to or supported by it inside the building must be inspected for possible evidence of rot and helped to dry out, as described below. Such walls may be affected externally and internally by fluffy white staining known as efflorescence, caused by salts within the stone or brickwork moving to the surface. It is not harmful and should disappear in time but if thought unsightly it can readily be removed using a dry brush.
When stone is seen to be eroding on an inside wall it may well be due to excessive condensation rather than to moisture from outside. The remedy is to ensure good air circulation and a regular, even temperature and to avoid the use within the church of those types of heater which give off a great deal of water vapour.
Look out also for any cracks in your walls. If any exist, check whether they have been spotted in a previous professional inspection and, if so, whether any action has been recommended and followed up. Should they appear to be new, there may be no immediate cause for concern if they only affect a single block of stone or brick but should new cracking run through several blocks or in a zigzag pattern through mortar jointing this will very probably indicate a more serious problem, due perhaps to subsidence or failure of some structural nature. Similar cracks that suddenly appear in window and door cills and lintols are also suspect, and should always be looked out for in your inspection. You should then promptly seek experienced architectural or engineering advice as to the causes and remedies. Bulging of a wall is also a sign of possible structural trouble and the same advice applies.
In framed buildings the main loads are carried by the framing, with the rest of the wall consisting of non-structural cladding panels.It is normally more urgent to deal with distress in the frame members (concrete, steel or timber) than with defects in the panels which are less important to the stability of the building.
At the foot of the wall it is good practice to have a gravel-filled trench immediately next to the building to enhance protection against rising damp and to help unexpected overflows from pipes and gutters to drain away harmlessly.
For the same reason, hard surfaces such as tarmac paths and parking spaces should preferably be kept free from abutting the building, especially when not well sloped to drain away from the structure. If possible, find out and record the layout of the underground drainage around the building in case it needs attention.
Plants, especially self-seeded trees, should not be allowed to grow against the walls and their root growth can also further damage leaking underground drains. Ivy growth should likewise be discouraged. Its roots can penetrate and break down mortar pointing. Remove it by cutting main stems and letting it die back naturally.
Harl is the traditional lime based rendering, put on like an overcoat to give added protection to less finely-built exposed masonry and/or to unify or accentuate the appearance of a building. One of the most familiar sights in the Scottish countryside is still the small white-harled kirk standing out against a darker landscape. Harl will usually have been applied with good reason and should not be thoughtlessly stripped off purely because the underlying stonework might be thought more attractive. This and other renders must be mixed with a suitably high proportion of lime in order to let the wall ‘breathe’ moisture in and out. Many mistaken attempts have been made to apply impervious finishes instead, notably cement-rich renders. They will come away in time as water nevertheless finds ways of penetrating behind, often removing a layer of stone in the process.
If good harling has been accidentally damaged, its composition should be analysed and the same mix used in the repair. It is advisable to seek the advice of a knowledgeable professional or masonry contractor before deciding to completely remove and replace poorer work.
If Masonry Paint is needed for redecoration, use only a mineral-based type and think carefully before painting wall surfaces simply for the sake of appearance when they have clearly not originally been intended for such treatment. Only use limewash or distemper as a finish for lime plasterwork.
Never accept without question claims for the effectiveness of proprietary waterproof products, usually transparent silicone-based treatments, promoted as protecting walls against damp for many years to come. If at all effective to begin with, they will not in fact last long and are most unlikely to give value for money. In some cases they can actually make problems worse.
POINTING is the technical term for applying mortar to masonry joints, including stone and brickwork. Mixes using Portland cement may be appropriate for more modern types of brickwork but a lime mortar should generally be used for work on sandstone walls. When a mortar is harder than the stone it will cause the adjoining material to break or peel away and will not adhere properly over time, allowing water to pass through the joints. Since different types of stone vary greatly in hardness, the mortar to be used will differ from one building to another. For lime to set, a hydraulic input is needed. In certain cases this can be achieved by using some cement in conjunction with the lime. Where walls are of soft sandstone,a hydraulic type of lime should be used with sand to make a suitable cement-free mortar.
Where hard mortar has already been used, the only sound long-term remedy is to rake it out and to repoint using a mix of water, lime, sand and small gravel suited to the consistency of the particular stone. In very fine joints the work may be completed by a shallow application of pure lime putty.
The Scottish Lime Centre can advise on suitable mixes. It is, however, important to understand that even NHL5, the most hydraulic lime, requires temperatures well above freezing for several days in order to set properly.
STONECLEANING is not recommended except in very special circumstances as nearly all methods damage the stone in some way. Washing with a bristle brush is sufficient. If the stone is stained and dirty, look for the reason and remove the cause if it is due to poor maintenance.
Biocides may be used to remove algae and moss – again, examine the reason for its presence. Applying a salt solution may also be effective. It is noticeable how such growth is rare in a salty seaside atmosphere.
Lastly, when engaging a masonry contractor to undertake stone repair, make sure that the firm has the necessary skills. If in doubt, ask to look as previous work.The individual or team employed must be able expertly to match in the new work by maintaining joint widths and profiles and by replicating surface finishes. Where the wall has been built, for example, with smaller pinnings between the blocks this should be repeated, using the least amount of mortar necessary.
Window and Door Openings
In unframed masonry walling any large opening will introduce a point of weakness meaning that particular attention must be paid to keeping out rain and draughts.
The weight of the structure above will need to be carried across each opening to transfer it back to the walls. Arched openings achieve this neatly by specially cut or moulded wedge-shaped stones or bricks (voussoirs) but rectangular openings require extra help in the form of beams or lintels. In traditional construction two of these are often combined across each door or window. An outer length of masonry built into the front thickness of the wall is reinforced by a second inner timber beam known, not always accurately, as a safe lintel. Like any timber product it will be vulnerable to unseen decay, especially since it will be concealed externally by its companion lintel and will probably also be hidden inside by plaster or another wall finish. Failing safe lintels should therefore be replaced in concrete or steel rather than being repaired or refitted in wood. Some stone lintels have an upper relieving arch of thin voussoirs to take the weight off their centres. These features can be surrounded by small stone pinnings in clay mortar, designed to absorb any movement and thus protecting the lintel from cracking. Such areas should not be filled with cement or lime but be pointed again with clay, although lime might be used for surface pointing to maintain a consistent appearance overall.
CHURCH WINDOWS come in a great variety of shapes and forms. Made usually of wood, moulded stonework or sometimes metal they range from the simplest utilitarian types to stupendous examples of the skills of the mason and the stained glass artist. Standards of construction also vary greatly.
Durable wooden frames can last for many generations with only minor repair if any. They may not be so reliable in cheaper construction and particularly not in churches built or repaired in the aftermath of World War 2 when high quality, well-seasoned timber was hard to obtain.
Such windows may well need complete replacement when time shows up their defects but be wary if advised that older or better-specified examples should be discarded. A good joiner will be able to repair many a window frame that is partly rotten at less cost than buying and fitting a new one which will very likely have to be purpose-made. Their sills tend to be vulnerable and may need painting more often than the rest of the frame. Reject new hardwood sills containing knots. These can shrink and allow water penetration. Make sure that any saddle bars fit safely into their reveals.
Metal Frames can be stressed, for instance, by warping and twisting caused by temperature variations over time. Repair may be possible but windows of the same design may still be made by firms such as Crittalls if needing replacement. Expect modern replacement designs to offer better heat and sound insulation. Opening lights can be draught proofed if necessary.
For every type of window it is important to keep an eye on all mastic and putty sealing and to maintain it intact against moisture penetration.
As you would at home, ensure that excessive repainting of wooden or metal frames has not sealed up opening lights, so preventing ventilation or proper closure.
And think carefully before replacing your windows in uPVC plastic which is likely to spoil the character of all but the most ordinary church building. Unlike timber it has the serious drawback of being difficult or impossible to repair. It also includes high embodied energy and has no such assurance of long life.
External DOORS should undergo regular redecoration and other necessary overhaul. Watch for rust and other difficulty with iron fittings, hinges and locks as part of your regular inspection. A good joiner will be able to piece in new timber to remedy damage to wooden doors.