As with repairs to chimney stacks, only the competent and confident handyman should attempt roof repairs. Safety is even more important in this case, since you will be working on the roof slope without even a friendly chimney stack to hold on to. Roof ladders are essential unless the repair needed is within easy reach of the eaves, and all access equipment should be secured. Tools needed are fairly limited — a hammer, a number of timber wedges and a tool called a slater’s ripper if you are working on a slate roof.
Refixing loose slates
Slates are held in place on the roof slope by nails driven through their centres or their top edges into battens. They usually slip because these nails have rusted away, or because the slate has split near the nail hole. It is usually possible to slide a slipped slate back into position, and to secure it with a strip of lead or other metal called a tingle. First you must slide the old slate out completely, allowing you to nail the tingle to a batten through the gap between the two slates underlying the one you removed. Then the old slate can be eased back into place, with those above it wedged up very slightly to give enough clearance. When the slate’s lower edge is aligned with others in that course, the end of the tingle is bent up and folded over the lower edge of the slate to hold it in place.
If slates are cracked or badly split, the only remedy is to remove the damaged slate and replace it with a new one. To do this you need a tool called a slater’s ripper, which has a hooked end designed to be slipped up under the offending slate and around the nails holding it. By jerking the ripper downwards, the hooked blade is made to cut through the nail, so freeing the slate. Then the new slate is carefully pushed up into position and secured with a tingle, as already described.
Replacing loose and damaged files
Most types of tiles are held in place by nibs behind their top edges which hook over battens nailed across the roof slope, and by the weight of the tiles in the next course up resting on them. If the nibs are damaged, the tile will have to be fixed back in position like a slate, or replaced completely. But if it has simply been dislodged by high winds, you should be able to slide it back into place with the nibs hooked over their batten. In either case, you will probably have to wedge up surrounding tiles slightly to allow the offending tile to be replaced. Do this gently, or you may crack other tiles, which will then have to be replaced too.
Replacing ridge files and slates
Ridge tiles and slates are bedded in mortar, and may have to be reset if movement in the roof has cracked the mortar. The loose tile or slate should be lifted off, and all the old mortar chipped away. It should then be re-bedded in a mortar of 1 part cement to 3 parts sand, laid along the ridge. Place the tile on this, tamp it down carefully, level with its neighbours, and finish off by pointing up the gaps between it and them and along the ridge tiles’ lower edges.
Waterproofing pitched roofs
If a tiled or slated roof is in poor condition, with a lot of loose and missing tiles or slates that have become porous with age, the only satisfactory long-term remedy is to have the roof stripped and re-covered. But you can make a short-term repair by covering the entire roof surface with bitumen emulsion, bedding a coarse scrim material in the emulsion and applying further coats to form a waterproof skin. There are a number of proprietary systems available for this purpose.
At eaves level, the ends of the various roof timbers are protected by planks of wood. Fascia boards are nailed to the cut ends of the rafters at the eaves, while bargeboards protect the ends of the roof purlins and tiling battens at the gable end of a roof. The barge and fascia boards will have their inside faces flush with the house wall if the timbers are cut off flush with the masonry; where the timbers protrude to give overhanging eaves, there will be soffit boards fixed at right angles to the fascia and bargeboards to fill the gap between the board edge and the wall. All this wood is prone to attacks of rot.
Replacing fascias and soffits
Since the house gutters are fixed to the fascia boards, these must be taken down first. You can then prise away the old timbers with a crowbar or bolster, and extract any nails left in the rafter ends.
If you are replacing both fascia and soffit, the new soffit is cut and fixed first. It must be a perfect fit against the house wall, so timber slightly wider than necessary is nailed temporarily in place. A block and pencil is then used to scribe the wall’s contours on to the soffit board, which is then cut and nailed into place. Next, the fascia boards are cut and nailed into place so that their lower edges protrude beneath the soffit. Joins between adjacent boards are made over a rafter end, and should be tightly butted together to prevent water penetration. The guttering can then be re-fixed.
You follow much the same procedure to replace bargeboards, fitting new soffits first if needed. At this point, a shaped tailpiece must be cut and nailed to the lower end of the bargeboard to fill the gap between it and the horizontal soffit behind the fascia.
Preserving the new wood
Because fascias, soffits and bargeboards are so exposed to the weather, it makes sense to try to prevent rot from getting a foothold in your newly installed wood. Use timber that has been preservative-treated by your timber merchant.
Flat roofs are usually constructed of several layers of roofing felt bedded in bitumen mastic or hot bitumen and covered with a layer of chippings rolled into a further bitumen layer. Joins between adjacent sheets of felt are overlapped rather than butted, and are arranged so that joins in successive layers do not coincide causing a weakness.
If a flat roof starts to leak, pinpointing the trouble can be extremely difficult. Begin by scraping off as many of the chippings as possible, and inspect the roof for signs of splits or other damage caused, for example, by ladders standing on the roof. You may find blistering where water has penetrated beneath one or more of the felt layers; these should be slit with a sharp knife so that bitumen emulsion can be brushed underneath the edges and the felt re-stuck. The damaged patches can be cut out and a patch of new roofing felt let in, bedded in bitumen emulsion. Then in all these cases the entire roof surface should be coated with a further layer of bitumen emulsion and the chip-pings replaced.
Re-covering a flat roof
If repairs and all-over waterproofing do not work, you will have to re-cover the roof. Begin by folding up flashings where the roof meets a wall, and then cut and strip all the old felt. Inspect the roof timbers beneath, replacing any that are showing signs of rot. Then lay the first strip of felt so that it just overlaps the edge of the roof above the gutters, and nail it at 150mm (6in) intervals all over. Lay succeeding strips so that they overlap by at least 50mm (2in) to complete the first layer.
Start laying the second layer at a slightly different point, so that the joins do not coincide with those in the first layer. Spread the bitumen mastic all over the roof surface and lay the felt in it, treading it down all over to fix it firmly in position. At the roof edges, allow the felt to overlap enough to reach into the gutters after being folded up into a double tongue and nailed to the verge batten. This will prevent water from running down the fascia boards. Finally, spread another layer of bitumen emulsion and tread down the third layer of felt, again avoiding coinciding seams. Finish off by folding down existing flashings or fitting new ones and spread another layer of bitumen to hold the final layer of stone chippings.