August 2020

Perfectly Pitched
“To strip a new roof and
re-install it is
expensive,
inconvenient, and
wholly undesirable”
installed correctly, though there were a few ridge
unions which had not been fully screwed down
onto the ridge tiles, leaving them vulnerable to
dislodgement in high winds.
Above: This image shows a tile without a clip.
Above: Only the left-hand verge tiles are clipped.
Continued from page 26
All the left-hand verge tiles are secured by head
nailing and verge clips. Therefore, the fixing of the
left-hand verge tiles complies with BS 5534 and
the manufacturer’s recommendations.
There are no verge clips on the right-hand verge
tiles, which is what prompted the investigation.
Standard verge clips, such as the ones used on
this development, are fixed onto the ends of the
tile battens and wrap around the outer edge of
each tile to secure it, meaning the clips are
visible when installed.
Technically, if each right-hand verge tile had been
head nailed and clipped using a tile clip (tile clips
are not visible once installed) then the fixing
would comply with BS 5534. Unfortunately, on the
roofs inspected, the roofer has not used tile clips,
therefore the fixing of the right-hand verge tiles
does not comply with the Standard.
Dry ridge system
The dry ridge system is a universal type, i.e.
designed to fit most common ridge tile profiles.
Generally, the dry ridge system appeared to be
The ridge union is not securing the ridges.
Remedial works
Unfortunately, in most cases, the only way to
bring an incorrectly fixed roof into compliance
with BS 5534 and the manufacturer’s fixing
specification is to remove the roof tiles and reinstall
them using the correct fixings. Roof tile
nails and clips are generally designed to be fitted
as the roof installation progresses, so it is not
usually possible to mechanically fix tiles with the
surrounding tiles in place.
To strip a new roof and re-install it is expensive,
inconvenient, and wholly undesirable, not to
mention the potential contractual disputes
which will inevitably arise. So clearly, getting it
right first time is crucial.
Summary
• Make sure all perimeter tiles, i.e. at verges, eaves,
ridge, abutments, each side of hips and valleys, are
twice fixed. For cut tiles, seek the roof tile
manufacturer’s guidance on how to fix these. Some
manufacturers provide special clips for cut tiles.
• Always obtain a manufacturer’s fixing
specification for every roofing project and, most
importantly, follow it.
• When using dry fix ridge and hip systems,
follow the manufacturer’s installation instructions
and take care to ensure that all ridge and hip tile
fixings are done correctly and securely.
Contact John Mercer
www.johnmercerconsultant.co.uk
@Johnmercer3
28 TC AUGUST 2020