Roofs

Slate came to dominate the roofing of Wales only in the nineteenth century. Before roofing slates were mass-produced and widely distributed, there was considerable regional variety, elements of which still survive: stone-tiled roofs are still relatively common in parts of Monmouthshire and the Bannau Brycheiniog (Brecon Beacons) as well as on older houses in the south Wales Valleys, for example, whilst thatch can still be found in parts of west Wales and Glamorgan. Thatching was an intensely local tradition, and different areas had their own techniques both for applying the thatch and for finishing the roof. Longstraw and combed wheat reed were the traditional materials, with a variety of underthatch ranging from straw mats in Glamorgan, to straw rope in north Pembrokeshire and Ceredigion, and heather, gorse or woven twigs elsewhere.

Although slate prevails over much of Wales, slate roofs are by no means uniform in appearance. Different quarries produced slate of quite different colour and texture and, in addition, it was only from the later nineteenth century that uniformly sized machine-cut slate became ubiquitous. Early slate roofs used hand-cut slates in a variety of sizes laid in diminishing courses with the thicker and larger slates towards the bottom of the roof. Methods of fixing also varied, and in earlier roofs, slates were hung on wooden battens using wooden pegs in a single hole at the top of the slate. Later roofs were more often centre-nailed with two holes.

Roofs of small slates bedded in lime mortar are a distinctive feature of the western seaboard. Sometimes these roofs were also grouted with lime mortar (and later with cement) as a repair technique. In some areas, by contrast, there are roofs of very large slates. Local variations reflected what the builder could afford, and continue to add to a sense of place.

Other important distinctions lie in the details of finish. The treatment of valleys within the roof varied, as did handling of the ridge. Interlocking ridge tiles were often used on stone-tiled roofs, and the technique was sometimes translated into slate. Mortared ridges were also used, but, from the mid-nineteenth century, fired clay ridge tiles were mass-produced and widely available. Plain clay tiles for the body of the roof were also produced, but were never widely used in Wales until the twentieth century.

Another product of the industrial revolution was corrugated iron. It came into use in the mid-nineteenth century and made its appearance in domestic building primarily as a substitute for failing thatch, and was used as the original roofing (and walling) material relatively rarely. It has some claim to be considered as a traditional building material, and even has something of a regional distribution.

What to look for: 

Dips and other signs of movement in the underlying roof structure.

Suggested action:

Longstanding and stable undulations in a roof are not necessarily a problem, but any new or developing ones should be checked by a structural engineer.

Dips in a roof slope may indicate problems with the underlying structure, such as the use of undersized timbers. They may, however, be the result of natural movement that occurred as the roof timbers dried after the building’s construction. Dips add character to a building, so avoid packing the timbers to provide a level surface for re-roofing – unless there is a structural problem that needs attention or the undulations are so severe that they allow water to penetrate the roof.

------------------

What to look for: 

Slipped, broken or delaminated nailed slates

Suggested action: 

Nailed slates — Replace slipped, missing or damaged slates temporarily using ‘tingles’ — 1 inch (25mm) wide strips of copper, lead or galvanized steel — or proprietary clips.

A damaged slate can be removed using a tool called a ‘slate ripper’ to cut the nails. To use a tingle to replace a slipped or missing slate, nail the top end of the tingle to the slate batten or boarding between the slates of the course below. Slide the replacement slate into place and bend the bottom edge of the tingle tightly over the lower edge of the slate to hold it in place. Proprietary clips may be used on a battened roof as a discreet alternative. These are similar to tingles, but are fixed through the nail holes in the slate.

A common cause of slipped slates is rusting of the iron nails used to fix them. This is known as ‘nail sickness’. If many slates are missing, consider re-roofing using copper or stainless steel roofing nails of suitable length.

-------------------

What to look for: 

Slipped, broken or delaminated pegged slates or stone tiles

Suggested action: 

Replace slipped, missing or damaged slates or tiles after determining the cause of failure.

Localized failure is usually due to the deterioration of the pegs used to fix the slates or tiles, or decay of the battens themselves. If the pegs have perished, they should be replaced with split oak whittled to the correct size.

To replace a missing slate or tile where the batten is sound, replace the oak peg if needed. Gently lift or push the surrounding slates or tiles aside and slide the loose one, or a matching replacement, back into position. Make sure that the peg is hooked over the batten.

If many slates or tiles are missing, particularly as a result of batten decay, consider re-roofing.

Damaged stone tiles may be cut down in size and re-dressed for use elsewhere on the roof. If replacement tiles are needed, it is important to bear in mind that stone tiles can be made from any suitable fissile stone, including sandstone or limestone. It is essential to make a good match with the existing tiles. Further advice on suitable sources is available from the Stone Roofing Association (www.stoneroof.org.uk).

-------------------

What to look for:

Slipped, missing or damaged clay tiles

Suggested action: 

Replace slipped, missing or damaged tiles using appropriate fixings.

Clay tiles can be either plain or profiled. Plain tiles can be found throughout Wales and are frequently seen on the roofs of Victorian churches. Profiled tiles are less common and tend to be more characteristic of south-east Wales.

Ordinary clay tiles are fixed in place using either oak pegs, hooked over tile battens, or nails. Nibbed tiles have small lumps of clay at the top edge, which can be hooked over battens like pegs. They also have holes to allow them to be nailed to the battens in exposed locations.

To replace a missing pegged or nibbed tile, gently lift or push the surrounding tiles aside and slide the loose one, or a matching replacement, back into position. Make sure that the pegs or nibs of all the tiles moved have been securely hooked over the battens. If new pegs are needed, they should be made from split oak whittled to the correct size.

Replace nailed tiles in the same way as nailed slates, using clips or tingles.

Avoid replacing handmade tiles with machine-made ones as they are unlikely to be a good match. If many tiles are missing consider re-roofing.

------------------

What to look for:

Grouted slate roofs – cracked, loose or missing grouting

Suggested action: 

Check the condition of the grouting both internally and externally for signs of cracking.

Grouting was used historically to repair failing roofs. A coat of lime mortar was applied to the exterior of a nailed or pegged slate roof to prevent the slates from lifting and to keep out wind-blown rain and snow. In Wales, it is mainly restricted to the western seaboard and it is a prominent feature in parts of Pembrokeshire. Nowadays, a slurry coat of cement is often used, but this can crack, allowing moisture to penetrate. If the roof is otherwise sound, cracked or failing grouting can be repaired by recoating the roof with a wet mix of cement or lime mortar.

------------------

What to look for: 

Thatch – loose material or signs of decay, particularly around the ridge

Suggested action: 

Seek advice from an experienced thatcher familiar with local traditions.

Longstraw and combed wheat reed are the traditional thatching materials in most parts of Wales. Both can be patch repaired or given an outer coat of new thatch. Neither should ever be stripped and replaced by water reed, as the under layers may date back as far the medieval period. Galvanized wire netting may be needed to protect the thatch from wind, birds and rodents. Make sure that the fastenings are not so secure as to prevent the fast removal of the thatch in the event of fire.

It is important that regional thatching traditions, designs and materials are retained. Ridges, for instance, need replacement on a fairly regular basis. The elaborately patterned block ridge, which is now the norm, has only been common in Wales since the 1960s. Traditionally, ridges were much plainer and flush with the roof slope.

Repairs should only be undertaken by an experienced thatcher. Try to find someone with a good working knowledge of the particular materials and the traditions local to your area.

------------------

What to look for: 

Corrugated iron – loose, rusting or holed sheets

Suggested action: 

Re-fix loose sheets, eliminate sources of moisture that may cause corrosion and renew protective coatings if necessary.

Corrugated iron is a traditional and versatile material that has been in production for nearly 200 years. It is often undervalued simply because it is commonplace and mainly used on vernacular buildings – those built in a traditional local style – or agricultural buildings. It is used as both roof and wall cladding. It is also sometimes used to replace or to overlay thatched roofs — a number of examples survive in Ceredigion.

The galvanized finish of corrugated iron is susceptible to failure through contact with moisture, leaving a rusty, corroded surface. Avoid the build-up of vegetation and debris, which traps moisture against the sheeting. Check junctions with other materials regularly as it is difficult to achieve a weathertight seal. Rainwater run-off from rusted corrugated sheeting can stain other materials. Condensation can also cause rusting of the underside of the sheeting so make sure that there is enough ventilation.

Traditionally, corrugated iron was usually coated externally with red lead paint, bitumen or tar to protect it against rust, producing the red or black colours that are so characteristic of corrugated iron roofs. These materials are still available for use, and should be reapplied if an existing coating has weathered or cracked.

If sheets need replacement, they should be of the same size and profile as the original ones. They should be secured with purpose-made galvanized nails and washers to give a waterproof seal.

-------------------

What to look for: 

Blocked roof ventilators or leaks around rooflights and lanterns

Suggested action: 

Clear leaves and debris from ventilators and from around rooflights and lanterns.

Roof ventilators should be kept clear at all times; if necessary install netting internally to prevent birds getting in. If safe access is possible, clear away any build-ups of leaves and debris, and make sure that the lead flashing around features is sound. Check timber elements for signs of decay and replace on a like-for-like basis as necessary. 

What to look for: 

Ridge and hip slates or tiles — loose, damaged or missing

Suggested action: 

Replace slates or tiles using hydraulic lime mortar.

The Victorians produced many highly decorative patterns of ridge tile, particularly in clay. Although the loss of decorative cresting on ridge tiles is unlikely to affect the performance of the ridge, it may be desirable to replace damaged tiles for aesthetic reasons, provided that matching tiles can be found. If appropriate replacements cannot be found to fill gaps on the main ridge or in other prominent locations, it may be acceptable to move tiles from less visible parts of the roof. Although the Victorians introduced a mortared overlapping ridge tile, the dry (unmortared) interlocking ridge and hip tiles now produced are not suitable for use on historic buildings.

---------------------

What to look for: 

Lead ridges and hips — lifted edges, holes, tears and signs of pitting or corrosion.

Suggested action: 

Use binoculars to inspect lead thoroughly for lifted edges, tears, holes and corrosion.

If the free edges of lead hip and ridge rolls are lifting, but the lead is otherwise sound, they can be dressed back into position. Secure them, if necessary, using tinned copper or terne-coated stainless steel clips. These consist of metal strips, which are slid under the lead sheet and fixed to the batten below using copper or stainless steel nails. The lower edge of the clip is folded over the edge of the lead sheet by a minimum of 1 inch (25mm). Clips should be spaced 12 to 20 inches (300–500mm) apart, depending on the level of exposure.

Damaged lead should be repaired or replaced by a plumber or lead roofer. Repair tape and mastic are not durable materials and are suitable only for very temporary emergency repairs.

New leadwork should be coated with patination oil in accordance with the manufacturer’s instructions. This prevents the formation of white lead carbonate, which can look unsightly and stain the materials below. This treatment will not need to be repeated.

---------------

What to look for: 

Mortar fillets at hips — loose or missing mortar

Suggested action: 

Use binoculars to inspect mortar fillets at the hips of pegged-slate and stone-tiled roofs and repair where necessary.

The hips on pegged-slate and stone-tiled roofs may be formed using lime or cement mortar fillets. Their condition should be checked regularly as fillets are highly susceptible to damage, allowing water to penetrate to the underlying roof timbers. The introduction of lead soakers – sheets of lead placed under the tiles at a join – can provide additional protection from the weather.

Missing or defective mortar fillets can be replaced using hydraulic lime mortar.

-------------------

What to look for: 

Timber finials or pendants — damaged, decayed or missing

Suggested action: 

Inspect with binoculars and repaint or repair if required.

The ridges of Victorian buildings, in particular, often have finials projecting above the gable ends or where the ridge meets the hip. They are sometimes made of clay, especially on hipped roofs, but on gabled roofs they are more frequently of squared or turned timber. Timber finials on gable ends sometimes extend downwards, the lower section being known as a ‘pendant.’

Timber finials and pendants are exposed to the weather and are susceptible to decay. Along with other external joinery, they should be painted at least once every 3 to 4 years

What to look for: 

Lead valleys — accumulated leaves or debris; slipped, damaged or corroded lead

Suggested action:

Remove leaves or debris using wooden or plastic tools to prevent damage to the lead. Arrange for damaged lead to be repaired or replaced.

Repairs to lead valleys should be carried out by a plumber or lead roofer. Repair tape and mastic are not durable materials and are suitable only for very temporary emergency repairs.

New leadwork should be coated with patination oil in accordance with the manufacturer’s instructions. This prevents the formation of white lead carbonate, which can look unsightly and stain the materials below. This treatment will not need to be repeated.

---------------

What to look for: 

Junctions of roofs and walls — damaged or missing mortar fillets

Suggested action: 

Replace damaged or missing mortar fillets with hydraulic lime mortar.

The junction between a roof and a rising wall, which is known as an ‘abutment’, can be vulnerable to water penetration. Lead flashings are much more effective weathering details than lime or cement fillets, which can crack and fail. However, flashings were only introduced in the eighteenth century. On older buildings, where it may be necessary to retain mortar fillets for aesthetic reasons, and on stone-tiled roofs, lead soakers installed beneath the roof cladding will provide discreet additional protection.

-----------------

What to look for: 

Junctions of roofs and walls — loose or damaged lead flashings

Suggested action: 

Reseat loose lead flashings and point with hydraulic lime mortar.

Lead flashings that have come loose where they are fixed into the wall can be repaired using pieces of lead sheet about 1 inch (20-25mm) wide. These should be folded over several times to create a wedge suitable for the thickness of the masonry joint.

The flashing should be folded tightly into the joint to a minimum depth of 1 inch (25mm) and the wedge knocked in to hold it in position using a hammer and plugging chisel. The spacing between the wedges should be no greater than 18 inches (450mm). On stepped flashings one centrally positioned wedge on each step is usually enough. The joint in the stone or brickwork should then be pointed with lime mortar.

If new leadwork is required, it should be coated with patination oil in accordance with the manufacturer’s instructions. This prevents the formation of white lead carbonate, which can look unsightly and stain the materials below. This treatment will not need to be repeated.

What to look for: 

Verges — loose or missing pointing or slates

Suggested action: 

Replace loose or missing pointing with hydraulic lime mortar and replicate original detailing when repositioning slates.

The edge of a pitched roof where it projects over a gable wall is known as a ‘verge.’ There are several different historic finishes for verges.

The simplest is where the edge of the slate or tile sticks out beyond the top of the wall. The gap between the roof cladding and wall is usually pointed up over a slate or tile undercloak. Replace loose or missing verge pointing using a hydraulic lime mortar mix.

Slate verges provide a more robust form of weatherproofing, and the technique is commonly seen on vernacular buildings. Here the detail is similar, but with the addition of small pieces of slate nailed vertically to the timbers at the head of the wall. Sometimes the slates are fixed just over the ends of the purlins – the horizontal timbers running the length of the roof – to protect the end grain of the timber. Replace loose or missing pieces of slate at the verges using copper or stainless steel nails. Make sure that the original detailing is replicated.

---------------

What to look for: 

Verges — weathered, decayed or damaged bargeboards

Suggested action: 

Check for signs of decay, cut out and replace rotten or damaged timber and redecorate if required.

Timber bargeboards were commonly used to finish verges on nineteenth- and twentieth-century buildings and can be highly ornamental. They should not, however, be used to replace other, more traditional verge treatments as their addition can radically alter the appearance of a building.

Bargeboards should be checked regularly for signs of decay. Rotten timber should be cut out and replaced with sections of treated softwood. Make sure that the dimensions and mouldings are identical. All painted joinery should be redecorated every 3 to 4 years.

--------------

What to look for: 

Open eaves — missing or damaged vermin guards

Suggested action: 

Replace missing or damaged vermin guards.

Eaves run along the bottom of a pitched roof slope. The underside may be left open with the rafters exposed. In such cases, birds can easily enter the roof space and vermin guards should be fitted to prevent them.

----------------

What to look for: 

Soffits and fascia boards — missing or damaged

Suggested action: 

Check for signs of decay, cut out and replace rotten or damaged timber and redecorate if required.

Eaves may be ‘closed,’ that is infilled with timber boarding or lath and plaster, to form a ‘soffit’. Closed eaves are further protected by a fascia board fixed vertically to the rafter ends. Do not install fascias and closed soffits where they have previously been open as this will significantly alter the appearance of a building.

Replace any rotten timber and ensure that fascia boards and boarded soffits are decorated at least every 3 to 4 years.

Where additional ventilation is required in a roof space, perhaps as a result of introducing insulation, the use of soffit ventilators should be avoided and a more discreet method used. Where fascia boards are present, it is often possible to install over fascia ventilators, which cannot be seen from the ground.

What to look for: 

Flat roofs and box gutters — build-up of leaves and debris; pooling of rainwater

Suggested action: 

Remove leaves and debris regularly, taking care not to damage the roof surface.

Clear roofs and gutters of leaves and other debris, particularly during autumn and winter. Also remove heavy falls of snow. Use wooden or plastic tools to avoid damaging the roof. Duckboarding can improve access, but it can also trap leaves and debris.

If pooling of rainwater continues after leaves and debris have been cleared, the fall of the gutter or the roof may be too shallow or uneven to allow water to drain away effectively. Consult an architect or surveyor for advice.

------------------

What to look for:

Lead roofs — leaks, tears and other signs of deterioration

Suggested action: 

Arrange for damaged lead to be repaired or replaced.

Lead sheet naturally moves quite significantly as a result of thermal expansion and contraction. On historic buildings it is common to find that oversized pieces of lead have been used. These tend to split as they cannot accommodate this movement.

Repair tape and mastic are not durable materials and are only suitable for temporary emergency repairs. Small tears and pinholes can, however, be repaired using lead. More seriously damaged leadwork or poorly draining lead roofs and gutters will need to be replaced in accordance with the detailed guidance provided by the Lead Sheet Association in its publication, Rolled Lead Sheet: The Complete Manual. Repairs should be undertaken by an experienced plumber or lead roofer. Welding requires particular care due to the potential fire hazard.

All new leadwork should be coated with patination oil in accordance with the manufacturer’s instructions. This prevents the formation of white lead carbonate, which can look unsightly and stain the materials below. This treatment will not need to be repeated.

------------------

What to look for: 

Bitumen roofs — leaks, tears and other signs of deterioration

Suggested action: 

Inspect the roof for signs of tearing, cracks, blisters or crazing and patch repair small defects.

Parapets, gutters, upstands, fixings and openings are particularly vulnerable areas, so check them carefully for leaks. Deterioration can be caused by a number of factors. These include thermal movement, lack of adherence to the underlying material, deterioration of the supporting substructure or poor workmanship at the time of installation. Small areas can be patch repaired, but re-roofing is likely to be necessary for more serious problems.

What to look for: 

Torching — cracked, loose or missing

Suggested action: 

Inspect the inside of the roof and repair or replace defective torching with hydraulic lime mortar containing hair.

Slated or tiled roofs on older buildings are often ‘torched’. This is where lime mortar is applied between the battens to the underside of the roof. Its purpose is to prevent the cladding from lifting and to prevent wind-blown rain and snow from entering the building. Water penetration and movement can cause torching to crack or fall off, so check the condition of the mortar, particularly after high winds.

Any defective torching should be replaced with lime mortar containing hair, which can be bought ready mixed. Torching can be applied in slightly different ways, so make sure that the original technique is replicated to give the same finished appearance.

Avoid any spray-on products that claim to provide insulation and protection from water ingress. They can seal roof voids, preventing ventilation and make subsequent leaks hard to trace. They are also extremely difficult to remove, so, when the building needs to be re-roofed, it will be almost impossible to reuse the slates or tiles. The same is true of bitumen-based external coatings.

---------------

What to look for: 

Roofing felt — torn or loose underfelt

Suggested action: 

Check that the underfelt is adequately dressed into gutters and inspect for holes.

Roofing felt is a relatively modern material designed to allow any water that penetrates the outer cladding to drain safely into the rainwater disposal system.

It can be damaged accidentally, but it may be possible to patch small holes. To do this, take an offcut of underfelt a little larger than the hole and tuck the lower edge behind the felt beneath the hole so that the new piece is between the existing felt and the roof cladding. Do the reverse above the hole so that the existing felt is between the roof cladding and the patch. This arrangement will help to ensure that if any water should get through the outer layer of cladding, it will run down the outer side of the felt and into the gutter, rather than dripping into the roof space. Tape the patch in place using duct tape.

If the felt needs to be replaced, it may be advisable to use a breathable material that will help to ensure adequate ventilation of the roof space. Take advice from a conservation architect or surveyor familiar with historic buildings.

What to look for: 

Roofing timbers — moisture staining on timbers and ceilings; signs of softness or decay, fungal growth, a musty smell or a distorted paint finish

Suggested action: 

Carefully check timbers, particularly where they are in contact with masonry, and seek guidance from a timber surveyor if any signs of decay or fungal growth are found.

Check that timbers feel dry to the touch, particularly where they abut or are built into external walls. Push the tip of a penknife or similar tool into the wood to check that the timber is sound.

Smoke blackening of timbers usually indicates that the building began life as a medieval hall house, with its hall open to the roof timbers. Smoke from the central open hearth escaped where it could through the roof covering. This blackening is not harmful to the timber. It is important evidence of a building’s history and should never be removed. Similarly, the use of microbore drills to test the structural integrity of timbers means that ‘defrassing’ — the removal of the powdery material on the surface — is rarely justified. Defrassing can seriously damage moulded timbers and should be avoided.

Look for signs of fungal growth, such as strands or cotton wool-like mycelium and fruiting bodies. Moulds do little damage to timber, other than to surfaces, but their presence is an indication that moisture levels are high and additional ventilation should be provided. There are, however, several species of fungi that can cause more serious decay. Confusingly, they are often classified as either ‘wet rots’ or ‘dry rots’, although both require a relatively high moisture content to take hold. Dry rots, in particular, thrive in warm, still and badly ventilated conditions.

The different types of fungi can be difficult to identify and their destructive capabilities difficult to assess. It is therefore important to ensure that rots are correctly identified so as to avoid unnecessary destruction of historic fabric.

Wet rots are generally less destructive than dry rots. Small areas that are accessible may be cut out and new treated timber spliced in.

As with all cases of fungal attack, the source of the damp that creates the right environmental conditions for rapid fungal growth must be tackled. Altering the environmental conditions is usually enough to kill wet rots, although the drying process can take months or even years. Dry rots are more difficult to eradicate and although they cannot survive in dry conditions, treatment also often involves the removal of all infected material and the use of chemicals.

If signs of decay or fungal growth are found, seek guidance from a specialist timber surveyor, rather than a timber treatment company. This way you can make sure that the advice you are given is independent and unbiased.

-----------------

What to look for: 

Roofing timbers — active beetle infestation (new flight holes and fine wood dust, known as ‘frass,’ on adjacent surfaces).

Suggested action: 

Carefully check timbers and seek guidance from a timber surveyor if any signs of beetle infestation are found.

Fungus breaks down the chemicals in wood and this can encourage beetle infestation. The possibility of both problems being present should therefore be considered.

There are several types of wood-boring insects that may be found in buildings. The most common are the common furniture beetle, or woodworm, and the death-watch beetle. The larvae cause the damage by burrowing through the timber, only coming to the surface when they are fully grown.

The adult beetle of both species can sometimes be found, particularly when an infestation is severe. Death-watch beetles also produce a characteristic noise by tapping their heads on timber during courtship. However, infestations are most commonly noticed when new flight holes and bore dust are observed. Furniture beetles most commonly attack the outer layer, or sapwood, of softwood species such as larch.

Adult beetles emerge between late May and August through round flight holes between 1/16 and 1/8 of an inch (1-2mm) in diameter. Death-watch beetles attack hardwood species, including oak, chestnut and elm. Adults emerge between mid-April to mid-June and their flight holes are about 3/16 of an inch (3mm) in diameter.

To complete their life cycle successfully furniture beetles and death-watch beetles need timber with a relatively high moisture content. To help prevent infestations, it is essential that roof spaces are kept dry and well ventilated.

If signs of beetle infestation are found, seek guidance from a specialist timber surveyor, rather than a timber treatment company. This way you can make sure that the advice you are given is independent and unbiased. This need not be expensive, but it could save you a considerable amount of money and disruption. It is pointless, for example, paying for wholesale timber treatment if the damage observed came from a beetle infestation that died out naturally many years ago. Unless an infestation is very slight, timber treatment will need to be carried out by a specialist contractor.

------------------

What to look for: 

Roofing timbers — movement or splitting of timbers and opening up of joints since the last inspection

Suggested action: 

If signs of movement are found, consult and architect, surveyor or structural engineer with experience of historic buildings.

These changes can indicate structural movement. Consult an architect, surveyor or structural engineer with experience of historic buildings. Be aware of past alterations, which could potentially weaken the roof. The insertion of dormer windows, for example, may have involved the removal of sections of the purlins. Alternatively, tie beams that help to prevent the trusses from moving outwards may have been removed or adapted to allow sufficient headroom to provide access between the bays.

What to look for: 

Roof spaces — Accumulated debris and birds’ nests, mouse or rat droppings, chewed electricity cables or other signs of infestation

Suggested action: 

Block entry points used by birds and vermin and remove debris.

Make sure that mesh is securely fitted over louvres and other openings to prevent entry by birds. Block entry points used by vermin and treat infestations. Arrange for chewed cables to be replaced immediately by a qualified electrician. Remove debris, but avoid disturbing nesting birds. Seek advice before undertaking any work, such as applying chemicals, when protected species, including bats and owls are present.

-------------------

What to look for: 

Roof spaces — bat droppings and urine stains indicating the presence of roosting bats

Suggested action: 

If you suspect that your building is being used as a bat roost, seek advice before undertaking any work that might disturb the bats.

Many old buildings are used as bat roosts. Particularly favoured roosting sites are at gable ends, above soffits, at the top of cavity walls near chimneys or behind bargeboards and fascia boards. The Wildlife and Countryside Act 1981 gives full protection to bats. It makes illegal the intentional killing, injury or handling of any bat or the intentional damage, destruction or obstruction of access to any place that a bat uses for shelter or protection. The Act does permit building maintenance and repairs to be undertaken with care. However, certain chemicals are banned as they are harmful to bats.

If the roof space is accessible, check for bat droppings, particularly at the gable end wall and along the eaves. They tend to accumulate beneath roosting sites or entry points. Droppings are dark brown or black and vary in length between 1/8 and 5/16 of an inch (4-8mm) depending on the species. However, they can be confused with mouse droppings, so if a roost is suspected, check externally for droppings on window cills or walls. Look particularly under the gable apex where the bats may be entering the roof space. Bats are most frequently seen flying at dusk on warm days between June and September when they can be observed emerging from the building.

If you suspect that your building is being used as a bat roost seek advice before using any timber treatment, fly killers or other chemicals. Protect textiles and polished timber surfaces that can be damaged by bat urine.

----------------

What to look for: 

Roof spaces — incorrectly installed or inadequate insulation

Suggested action: 

Check for signs of condensation or inadequate ventilation.

Check at the beginning of each winter that loft insulation is correctly installed to cover the heads of walls. During spells of cold weather check for signs of condensation within the roof space, such as mould growth on roofing felt. Check to see if any ventilation is blocked. Make sure that any gaps around pipes and cables entering the roof space from below are sealed, particularly over kitchens and bathrooms where most water vapour is generated.

Although we are encouraged to install energy-saving measures, in historic buildings it is particularly important to find the right balance between heating, insulation and ventilation. Buildings constructed using traditional materials and techniques tend to be damper. The performance of the materials relies heavily on their ability to breathe. For example, a solid masonry wall built with lime mortar will absorb driving rain and release it slowly back into the atmosphere through evaporation. The thickness of the wall will help to prevent internal moisture levels from rising excessively. Similarly, the walling material will absorb moisture generated from within the building through porous finishes, such as limewash or distemper. The high level of ventilation usually found in older buildings and the use of open fires helps to control humidity levels and encourages evaporation.

On the other hand, modern construction techniques rely on the use of vapour barriers and sealants with limited ventilation being provided by extractor fans or trickle vents. The use of such techniques in older buildings can trap moisture with disastrous effects. Unless adequate ventilation is provided, measures to reduce heat loss can create problems with condensation, mould and fungal growth, which can create health problems. Condensation is often misdiagnosed as rising or penetrating damp.

Several types of material are used for loft insulation, ranging from sheep’s wool to fibreglass. They come in either rolls or bats and are easy to install within the roof space over the ceiling joists of the top floor. Quilts should be installed underneath electric cables in order to avoid any risk of heat building up. Do not insulate underneath water tanks as they need the slight warmth from below in order to avoid freezing, but the sides and top must also be lagged.

A ‘thermal bridge’ – a path of least resistance along which heat is transferred – will be created if the insulation is not also laid over the heads of walls. As water condenses on the coldest surface, the creation of a thermal bridge will concentrate the moisture in this area. If the insulation cannot be correctly detailed and additional ventilation cannot be provided to compensate, particularly where roofing felt has been used, it may be better not to insulate at all.

As insulation tends to reduce the temperature inside the roof space, the risk of condensation is increased. Moisture from within the building should therefore be controlled and any points sealed where it may gain access into the roof space, such as holes around pipes and cables.

If you are considering insulation that follows the rafter line, such as in an attic with habitable rooms, the installation is complex. It will require a ventilation path below the roof cladding, the insulation itself, a continuous vapour control layer and an internal lining. The detailing must be correct and specialist advice should be sought to ensure that the design is appropriate for your building.

Avoid all spray-on insulation products. They reduce ventilation and can trap moisture within the rafters and battens. They can also prevent the reuse of slates and tiles when the roof cladding needs to be replaced.