On 24/11/2016 13:23, Chris J Dixon wrote:
There seems to be a move to retro-fit plastic dry verges these
days, with plenty of firms touting for business.

My cement tiled roof is due for some attention, and I don't do
aerial clambering.

Are they a good idea? What are they screwed into?

What sort of prices are reasonable? I am in a semi, but next door
is lower, so I effectively have two gable ends.

Unusually for me, I was curious enough to allow a caller at my
door to give me a price, which started at £550, then dropped by
£100. I've just had a flyer for another outfit (devoid of street
address) which would be £298.

What dodges do the unscrupulous use, about which I should be
wary?

Chris

Technically they are nonsense. A properly mortared end joint using
the correct amount of cement for bedding will last the life of the
property.

what is more important is the way the tiles and undercloak are
installed.

Small tiles need a hip effect at the end to stop water being
blown over the gable end and causing rot to the ends of the tile
battens and supports.

large concrete tiles like Marley Modern must be laid flat and
so the undercloak must tilt down about 3 degrees so that water
blown over the gable end runs down the outer edge and not
find its way back into and behind the barge boards.

Ask about 20 'roofers' how they install Marley Modern tiles
and you'll by lucky if even one knows the correct answer.
You should therefore assume that most of the people installing
dry verges, also haven't bothered to RTFM. A solidly mortared
verge is probably your best bet if you live in an exposed
area. In Southern Ireland it is standard practice to build
some shuttering along the end of the roof from ridge down
to gutter, infill with some chicken wire and create a solid
concrete slab about 8 inches wide and 4 inches deep to stop
extreme winds ripping the whole roof off.

Dry ridges and verges are used by the big builders because
it is quicker and looks tidy.

The storm we had in October 2013 ripped a few of these plastic
end panels off on a few houses where I live.