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The nice thing about a tiled roof is
that it can be dismantled and reassembled using the same tiles, if there
is an alteration to the building. But too often roofs need to be
repaired because they were not constructed correctly in the first
instance, or a secondary trade, such as the plumber/electrician, has
decided to install a vent, or flue, through the roof, and has removed
tiles and not re-fixed them correctly.
In many instances it may be correct to slide out the
affected/broken tile and replace it without nailing or clipping. But
what should you do if the tiles are fully clipped and nailed?
Reinstating the fixings can be difficult, but not impossible.
Interlocking variable head-lap tiles
If the tiles are nailed, or should be nailed, it is essential to
determine if the rafter pitch is below 45° or not. At 45° and above all
interlocking tiles must be fully nailed. Below 45° it is possible,
unless the wind uplift for the roof is very high, to install a tile clip
to the lower left hand interlock with some difficulty. This can be
achieved by nailing the clip into position with the hook resting in the
clip recess of the adjacent tile. The clip is held up with a trowel, or
similar thin implement, while the new tile is slid into place under the
hook of the clip. Once in position the trowel is removed releasing the
clip, which locates with the side interlock of the tile. Clips are
generally much more efficient at resisting wind uplift forces that a
head nail fixing.
If the tile must be nailed and/or clipped as well, the
solution is to measure the distance in, and the distance up from the
bottom of the tile, to position the nail hole in the tile. Next release
the clip on the tile above and slide the new tile into position. Mark
out the position of the nail holes of the tile below the replaced tile,
and the replaced tile, and drill a hole through the upper tile directly
above the nail hole to allow a screw with a cap and washer to be
installed through the two tiles and into the batten below. This should
be done twice for the head and the tail of the replaced tile. Depending
upon the thickness of the tile being replaced, the screw could be
between 40mm and 120mm long. If there are two nail holes and the tiles
are laid broken bond it is important to not drill through the side
interlock. Also the screw fixing should be either brass or stainless
steel. A coated steel screw is not suitable. Also the cap and washer
must form a waterproof seal around the hole; therefore careful drilling
and the insertion of a mastic sealant around the screw shank where it
passes through the lower tile would be advisable.
For resin slates, such as the Redland Cambrian slate,
there are repair kit systems that use special adhesives applied to
specific parts of the tile that bond the resin slate to the adjacent
slates and transfer the wind suction loads to them. These systems are
tile specific and the fixing instructions should be followed to the
Interlocking fixed headlap tiles
Generally speaking we are referring to clay pantiles that are laid
straight bond. If the tiles are laid broken bond then they should be
treated the same as variable head-lap tiles. With clay pantiles that
have the top right hand corner and bottom left hand corner shouldered it
is very easy to remove a vertical band of tiles down from the ridge to
the eaves as they can be easily rotated out to the left, once the head
nail and the clip, if it has one, have been removed.
Many clay tiles, especially old designs with no weather
bars and interlocks, have the nails driven in parallel with the rafter
through the nib, rather than the face of the tile.
With this type of fixing an individual tile
can be re-nailed using a Z-shaped drift, by inserting the nail in the
nail hole with the nail head resting on the nib. By positioning the tile
25mm up the roof under the raised corner of the tile to the top right,
the nail can then be driven in using the Z-shaped drift and a hammer,
much like using a sate ripper which eventually pulls the tile down into
its correct position.
It is possible to repair these tiles by drilling
through both tiles at the bottom of the pan directly above the batten.
This is the worst place possible to do such a fixing as all the water on
the tile is channelled to that point so should be avoided at all cost.
Clipping the bottom edge of the tile in an array is possible with a Z
clip, but the head of the lower tile must be head nailed.
In many instances plain
tiles are not nailed every row so it is quite easy to remove the two
courses of tiles above, re-nail the affected tiles and replace the
un-nailed tiles using a trowel. But where the tiles are all twice nailed
such as with vertical tiling, it is impossible to re-nail replaced
In this case the Marley Plain tile repair clip can be
installed to the tile, and using a special tool, the tile can be
installed with the clip clamping the tile to the batten. This clip only
works with 38 x 25mm battens and where the back of the batten is
exposed, i.e. not nailed directly to rigid sarking, or a wall.
Where tiles are fixed with annular ring shank nails, when they are
removed they will leave a torn hole. The new fixing should be either a
larger ring shank nail or screw fixing to achieve the grip in the same
There are some situations where it is not possible to head nail tiles,
such as with theMarley dry ridge system that has a plastic batten
section. In most instances it is possible to undertake remedial repairs
by using clips, or screw fixings, to comply with BS5534: The British
Standard Code of practice for slating and tiling. Most systems are
visible on completion, whilst others will be completely invisible.
Either way the right fixing method for the tile and situation needs to
be determined. Often stripping down from the ridge may just be easier
and quicker than getting the right remedial fixings (unless you have
them in your tool kit already).
- When drilling a screw hole through a
tile never use the hammer action facility, and always use a sharp
- Avoid using any plastic clips for
long term roof repairs as the plastic will age harden and may fail
- Never use coated steel screws or
nails to fix tiles onto a roof as the coating can be scratched and
rust will start to destroy the fixing.
by Chris Thomas, The Tiled Roofing Consultancy, 2 Ridlands Grove,
Limpsfield Chart, Oxted, Surrey, RH8 0ST, tel 01883 724774