How to Repair Pitched Roof

How to Repair Pitched Roof

The timber rafters of most pitched roofs measure 100 x 50mm. On roofs less than about 30 years old, the rafters are covered with roofing felt a type called reinforced (it has a layer of hessian cloth bonded into it) comes in rolls 20m long by lm wide. The fell is usually fixed to the rafters with galvanised felt nails 20mm long which have large heads. Each strip of felt should dip slightly between the rafters, overlap the next one further down the roof by at least 150mm, and the bottom strip should overlap the fascia so that it pokes into the gutter. On exposed roofs the rafters might be covered with wooden boards (called sarking) to give extra protection.

Battens are nailed over the felt across the rafters. The size of the battens depends on the type of roof covering to be used and how close the rafters are together: 38 x 19mm limbers are usually adequate. The battens should be treated with preservative and fixed with 50 or 65mm nails if steel ones are used they should be the galvanised type. Roofs covered with sarking need counter bat­tens- lengths of 38 x 6mm timber nailed parallel to the rafters before the main bat­tens are fixed.

The most common materials used to clad pitched roofs are slates, stone, tiles (plain or interlocking) and shingles.

Slates and plain tiles are overlapped so that each row overlaps the one below and the vertical joins in each row are stag­gered. They are nailed to the battens -preferably with aluminium, copper or silicon-bronze nails usually with two nails to each tile or slate. The amount of overlap needed depends on the pitch of the roof more overlap is needed for shal­low roofs. The head lap is the amount the tiles overlap the row-but-one beneath. The side lap is the distance from the side of a slate to the vertical gap between the slates in the row directly beneath. The gauge is the length of the slate or tile exposed on the roof and is the same as the batten spacing.

Natural slates, usually a blue-black col­our, were used on many older houses built around the turn of the century. Simulated slates are becoming popular on new houses and as replacements. These can cither be plain slates made from fibre cement (asbestos is no longer used) or reconstituted slate in resin with deckled edges.

Natural slates are available in many sizes usually from 255 x 150mm to 610 x 355mm and every one needs nail­ing to the battens the holes can be made with an electric drill fitted with a masonry bit. There are two positions for the nail holes.

Head-nailed slates have holes so that the head comes more-or-less flush with the top of the batten.

Centre-nailed slates have holes further down but not exactly central so that the head of the slate sits on the bottom edge of the batten, to make room for the nail from the slate.

Head-nailed slates are more likely to lift in strong winds, so this method of nailing is generally not used on shallow pitch roofs or with large slates. On the other hand, head-nailing is generally easier, though the nails are less easy to get at afterwards. Slates can be laid on a roof with a pitch as low as 20 degrees.

Reconstituted simulated slates can be laid single lap, they are held on to the roof with clips. They need a minimum pitch of 25 degrees.

Natural stone slates are no longer generally available, but reconstituted stone slates can be laid on roofs with pitches from 30 degrees.

Traditionally, tiles were made of clay, but since the end of the Second World War most have been made of concrete. Most houses are now roofed with interlocking concrete tiles, but plain tiles are still avail­able in both clay and concrete plus matching ridge or valley tiles. Plain tiles Some plain tiles are nailed to the battens, but most have small projec­tions called nibs as well which hook over the battens. Usually nailing every fourth or fifth row on the main part of the roof and exposed tiles a couple of rows at the ridge and eaves, and the tiles at the verges is enough. For plain clay tiles the pitch must be at least 40 degrees. Tiles are about 265 x 165mm and are very slightly curved.

Interlocking tiles

With these tiles the sides of the tile overlap each other so only one layer is needed. There are many different types depending on the pitch of the roof: most cope with pitches of 30 degrees, some with pilches less than 20 degrees. The sizes vary but 380 x 220mm is fairly common. Interlocking clay tiles (pantiles, for example) need a minimum pitch of around 35 degrees.

Shingles are a kind of wooden tile often made from western red cedar a wood which weathers to a silvery-grey colour. They are used on roofs and for cladding walls which need extra warmth and weather protection and are also more common on steep roofs where their visual appearance can be best displayed. The tiles are usually about 400mm long and taper from 8mm to1.5mm. They are available in a variety of widths.


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