This section of our site provides you with information on common faults with old roofs. We also have details on repairing these faults and advise you on the options of repairing or re-roofing.
We have also taken the time to provide you with a dictionary of roofing terms (to your right) which will assist you in understanding the roofing jargon we use in this section of our site.
We hope you find this section both useful and informative. Please contact us if you have any questions.
The life of a roof is finite; one should, therefore, acknowledge the fact that at some point in time it is liable to fail.
The first signs of deterioration in the roof covering are usually indicated by the presence of broken and delaminated slates/ tiles or daylight showing through to the loft area. Cracks and eventual breakage are caused by the effects of weather and movement within the roof structure, which increase as the fixings decay.
Delamination occurs with slates and clay tiles, which are of a laminated structure. Water, which is absorbed into the slate or tile during the winter, can freeze and expand, causing the layers to separate and flake off.
A roof, which has an uneven surface, gives a reasonable indication that the roof timbers and battens are sagging. This may be due to decay in the timbers caused by water ingress or settlement within the building structure. The end result is a general disturbance of the roof covering, producing strain on the fixings and breaking of mortar joints.
Slates or tiles, which have slipped, indicate deterioration in the fixings, which may be nails or wooden pegs. If slipping has occurred in several places on the roof, it must be assumed that all the fixings are in an advanced stage of decay.
On closer examination, it may be found that the bedding mortar used at the ridges, verges and hips is cracked and decomposing allowing movement and water penetration to take place. Metal flashings and valleys may also require replacement as erosion and fatigue can produce hairline cracks allowing water to enter, which is mostly caused by incorrect installation.
Mortar fillet flashings are cheap and were common before the 1940’s, but they are generally less effective than metal due to their durability and inability to accommodate minor thermal and structural movement, which causes cracking. They are also susceptible to frost attack, which also results in the cracking of the mortar fillet.
Any faults already mentioned will leave a roof vulnerable to water penetration and further deterioration. It is necessary to inspect a roof thoroughly before any major refurbishment work in other areas is started and any faults rectified by taking one of the alternatives, which follow.
If the faults are confined to small areas and the remainder of the roof structure is sound, replacement of damaged slates or tiles may be the answer.
There could be a problem in obtaining slates or tiles of similar profile and colour due to tile or slate designs becoming obsolete; second-hand slates or tiles would have to be found.
However, it must be remembered that patching will not prevent deterioration in other parts of the roof and frequent inspections and repairs may be required. Patching is ugly, inconvenient and impractical and the cost of small repair work will rise annually.
This sort of treatment should be regarded as an uneconomic long-term solution.
There are a number of surface treatments on the market designed to form a protective layer over slates or tiles. The coating compound is applied in a liquid state, which hardens off, sealing gaps and holding the slates or tiles in place.
This type of treatment does not remedy faults in tiling battens and rafters, which may continue to decay due to moist air becoming trapped in the roof space. Natural ventilation through the roof coverings is prevented and alternative methods would be required.
The life of the material is uncertain, and the British Standard B.S.5534 Slating & Tiling does not recommend the use of surface coatings either internally or externally.
Re-roofing offers many advantages over repairing. Upon the removal of the old coverings, the timber rafters can be closely examined, replacing and packing-up where necessary to bring the roof structure onto an even plane.
Roofing felt is installed providing a barrier against wind, driven snow, dirt from outside.
New battens, slates or tiles are laid, bringing the roof up to present-day standards and performance associated with newly constructed buildings.
Ventilation products are installed to provide adequate ventilation of the roof void in accordance with current Building Regulations.
| Term | Description |
|---|---|
| Abutment | The junction of a roof surface with a wall, or any other structural feature, which arises above it. |
| Barge Board | A board fixed along the edge of a gable. |
| Batten | Horizontal small section timbers that are nailed to the rafters and to which tiles/slates are secured. |
| Back Gutter | A gutter formed in lead at the back of a chimney, or any other structure, which penetrates the roof to disperse water onto tiles/slates. |
| Cold Roof | A roof that has insulation laid horizontally at ceiling level and a void between the insulation and its outer roof structure and covering. |
| Course | A horizontal row of tiles or slates. |
| Dormer | Framed window unit, which projects through the sloping plane of a roof. |
| Down Pipe | Pipe which takes water away from guttering to drains. |
| Eaves | The horizontal, lower edge of a sloped roof – where the first course of tiles/slates are laid on the fascia board. |
| Fascia Board | The horizontal timber trim attached vertically at the eaves that covers the rafter ends, the wall plate or the wall face. The guttering is fixed to this and upon which the first course of tiles/slates are laid. |
| Felt/Underlay | Untearable bituminous or PVC sheet material, supplied in rolls and laid over rafters. |
| Flashing | Strip of lead, used at abutments, to stop water penetration. The Code of lead means the thickness. |
| Gable | The upper portion of a sidewall, which comes to a triangular point at the ridge of a sloping roof. |
| Gauge | The length of tile/slate exposed after it has been installed. It equals the distance between the top of one batten and the top of the next. |
| Gutter | The trough that channels water from the eaves to the down pipes. |
| Headlap | The amount by which a tile/slate overlaps the course below it. |
| Hip | The meeting of two pitched roof surfaces, which meet at an external angle. |
| Hip Iron | A metal hook, which is secured to the roof structure to support the hip tiles and stop them from slipping. |
| Mortar | Sand & cement mix consisting of 3 parts sand to1 part cement. |
| Parapet | Low protective wall that extends above the roofline for support. |
| Pitch | Also known as slope, is the measure of how steep a roof is. The pitch of a roof is a big factor in determining the kinds of materials that can be used and the longevity of the roof. Usually, a steeper roof will last longer due to its better draining capabilities. |
| Purling | Main structural roof support timber: usually situated half way up the roof span: to which rafters are nailed. |
| Rafter | The supporting framing timber, sloping from ridge to wall plate. |
| Raking Cut | A diagonal cut across courses of tiles/slates. |
| Ridge | The uppermost horizontal junction of two slopes forming the apex of a pitched roof. |
| Saddle | A piece of impervious flexible sheet material (usually lead) dressed to shape, fitted to provide weather protection. |
| Secret Gutter | A gutter former at an abutment and effectively hidden from sight. |
| Soaker | A small piece of sheet (usually lead), shaped and inserted between double lap tile or slates on the abutment between a roof slope and a vertical wall. |
| Soffit Board | A board fixed to the feet of rafters, which forms the underside of projecting eaves. |
| Undercloak | Fibre cement strip, fixed at the verge beneath the battens, onto which the verge tiles/slates are bedded. |
| Underlay | A layer of material acting as a barrier between the roof covering and the sub-structure (see felt). |
| Valley | The junction of two inclined roof surfaces at an internal angle to provide water run-off; channel to allow roof slopes at different pitches to join together and discharge water into gutters. |
| Valley Gutter | A visible gutter running down the valley. |
| Verge | A free end of a roof surface; for example that at the end of a gable or dormer. |
| Warm Roof | A roof that has insulation and a vapour barrier laid above or between its supporting structure (normally on the pitch of the rafters), and immediately below its weatherproof membrane. |