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Restoring a roof can be a tricky business. Find out where to start, what techniques to use and how much the project will cost.
A worn-out roof not only looks shabby, but is just about the worst problem a property can have - because once damp starts to get in, it doesn't take long before the whole place starts to deteriorate. Apart from the immediate damage to cosmetic finishes such as decoration and plasterwork, damp conditions are the favourite of far nastier problems such as wet and dry rot.
Constantly exposed to the harsh impact of the environment, the roof is one of the most vulnerable parts of any building, and as such requires regular care and repair. Simple roof maintenance tasks include replacing missing or broken tiles or slates, and making sure that junctions in the roof are kept dry by inspecting lead flashings and mortar joints at all junctions. If left unattended, the serious problems that can result lead to far hire restoration costs.
Anyone buying a property to renovate should take a very close look at the condition of the roof to assess what, if any, work is required in order to be able to take the cost into account when assessing value.
How to assess the roof
Internal inspection: Most common roof restoring problems will show up as leaks inside the house. Look out for signs of damp on the walls and ceilings of the top-floor rooms. Plaster or wall coverings will be discoloured and may be coming away from the walls, and there are also likely to be signs of mould. If the problem has been left for some time, the ceilings may have bowed or even collapsed. If you see any of these signs the likelihood is that the roof covering is damaged or missing in places. The repairs may be relatively minor, but you need to see how extensively the damp has damaged the roof structure and the floors, as repairs here will be more expensive.
Even if there are no obvious signs of damp, you should inspect the roof structure internally with a torch. In a traditional roof that has not been replaced for several decades, you will be able to see the timber battens running horizontally over the secondary rafters, and the underside of the tiles or slates. This is because roofing felt, the secondary barrier now routinely used to protect against wind and rain, was not widely used until the 1940s. Any defects in the roof covering of an un-felted roof should be obvious because daylight will shine through into the darkened roof space.
Occasionally, you may see a roof where the space between the undersides of the battens has been filled with lime mortar strengthened with horsehair. Known as torching, this was done to keep out driving wind and rain, or as a repair to hold the tiles in place where the original fixings usually nails but sometimes wooden pegs have failed.
If the roof has been re-tiled, or the property was built after 1940, the rafters and tiles should be concealed by the under-felt and so signs of missing tiles will have to be inspected from outside; this is also the case where the underside of the rafters has been boarded, or where the attic has been converted.
External inspection: Other than when there are missing, broken or slipped slates or tiles - which you should be able to spot quite easily leaks are far more likely to be found at joints and junctions where two sections of roof meet, suchas a hip or valley, or where the roof abuts the wall or chimneys. Here, the joints should be waterproofed using lead flashing, also known as soakers, and/or mortar joints.
Repairs: Valleys should have a lead tray running beneath the tiles or slates, or more recently a fibreglass or PVCu tray. If this is damaged or missing, the tiles or slates will have to be stripped back and a new valley tray fixed in place and the roof covering replaced.
Hips should be covered with ridge tiles or bonnet tiles and these should be firmly bedded down on mortar. On some slate roofs the hips may be covered with rolled leadwork, laid over a broom handle section. If this is damaged it will need replacing.
Abutments (where the roof intersects with a wall or chimney) should have L-shaped lead soakers running from under the tiles and cut into the brickwork joints and then pointed in with mortar, with each course overlapping from the top down. On older houses, and where the roof tiles are uneven, e.g. limestone and sandstone, abutments were often filled with only a mortar fillet and these crack and fail easily, requiring replacement.
At the verges, tiles and slates should be bedded down on mortar, as should the ridge tiles.
Inspecting the roof
Infestation: Once you have inspected the roof covering, check that all of the main roof timbers are dry and solid and that there is no sign of rot or damage from wood-boring insects do not worry if you spot holes from wood-boring insects as they may be historic: what you are looking for is fresh sawdust.
Treatment and Repair: Any damaged timber must be removed and replaced. The structure will usually require chemical treatment to prevent re-infestation. Although many conservationists insist chemical treatment is unnecessary once the building is dry and the timbers moisture content below 20%, most lenders still insist this work is undertaken and a guarantee issued.
Structural Movement: Look out for gaps between major roof timbers such as the tie beams, rafters and purlins, ceiling/floor joists, or bowing walls: all signs that the roof might be spreading. If the walls of the building have moved, the principal rafter feet may no longer be sitting on the walls and this may eventually lead to roof failure.
Repair: If there are any signs that the roof has structural problems, the extent of repairs required will need to be decided by a structural engineer. Small sections of the structure may be removed by providing temporary support, but if whole trusses or rafters have to be replaced, part or all of the roof covering will have to be removed before the repair can be undertaken. Although this will add to costs, one benefit is that the roof can be felted properly, the whole structure inspected and battens replaced. It will also allow the inspection and repair of weak spots. If there are plans to convert the roof space, stripping the roof covering can also make it easier to incorporate insulation over the rafters.
If the roof has spread and pushed the walls out, pulling the structure back in to its original position is unlikely to be possible, and it is more likely that the walls will have to be stabilised using lateral restraint straps. The rafter feet can then be supported by steel brackets fixed to the walls, steel extensions running onto the walls, or alternatively, in some situations they can be bolted into the floor joists to prevent further spread. It may also be necessary to insert new horizontal cross-ties to prevent the trusses from spreading.
Repairing and Replacing Roof Coverings: Stripping and re-covering an entire roof is an expensive job and should be avoided unless absolutely essential. Replacing individual tiles or slates that are missing or broken is not a difficult or expensive repair, however it is important to find a good match for the rest of the roof.
Stripping tiles or slates will result in the loss of a good percentage of the material and an allowance must be made for this in calculating replacement costs.
Flat Roof Repairs: All flat roofs must have a slight pitch to help rainwater flow away. If the roof structure moves, this pitch can be altered, causing pooling. If the roof covering is not entirely waterproof, the standing water gradually finds its way through. Standing water can also be caused by blocked gutters or downpipes.
Spray-on Urethane Foam: An effective alternative to stripping and re-laying an un-felted and un-insulated roof is to use a spray-on urethane foam applied to the underside of the rafters. This adds a waterproof layer and insulates the roof structure and is, therefore, a cost-effective solution. This technique also fixes loose slates or tiles in place. The only drawback is that the strong bond can make the roof covering difficult to remove later when individual tiles or slates crack or spall and need replacing. It also prevents the slates or tiles from being salvaged in the future and so is not a technique generally favoured by conservationists.
Roofing contractors: Roofing contractors will repair or replace conventional roof coverings such as clay or concrete tiles, natural or artificial slates, and stone roofing. Most leave flat roofing and other, less common, roof coverings, such as thatch, metal and turf, to specialists. Roofing contractors generally work on a supply-and-fix basis and provide an all-inclusive fixed price quote taking into account the size of the tiles and the coverage.
Flat roof coverings have a tough job. They have to be totally waterproof, hard-wearing, resistant to tears, able to expand with the building, and also be resistant to damage caused by ultraviolet rays from the sun. The main choices are asphalt, built-up bitumen felt (usually with stone chippings on the surface), metal, glass-reinforced plastic (GRP), synthetic rubber and man-made single-ply membranes. For a contemporary look consider single-ply membranes or metal.
Modern Roof Structures: Many new houses built since the 1960s use modern roof trusses in place of rafters and purlins. They use much smaller sections of timber arranged in a web and connected using metal plates known as gang nails. Made from treated softwood, they should resist fungal and insect attack and so the only structural damage is likely to result from poorly undertaken alterations. For a renovator, the main drawback with fink trusses is that they do not lend themselves to adaptation for loft conversion without considerable work.
Article Courtesy: http://www.homebuilding.co.uk/feature/restore-roof
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Roof Restoring | Roofing Inspection | Roof Restoring - Learn about roof restoring & roofing inspection. Get prices from local roofers for roofing services
Roof Restoring | Roofing Inspection | Roof Restoring - Learn about roof restoring & roofing inspection. Get prices from local roofers for roofing services
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