Hi,

I have a flat garage roof that has started to leak. It currently has
chipboard beneath the felt, which has started to expand and rot. So I need
to totally replace the roof, replacing chipboard with 18mm WBP ply, then 3
layers of felt (2 underlay 1 top)
Now my question is, the 1st layer of underlay, should I nail it to the ply
boards, stick it, or leave it free moving. I read this website
http://www.diydata.com/projects/flatroof/flatroof.htm that says to nail the
felt every 6" (using proper felt roofing nails), however I was talking to
our 2 builders/maintenance contractors at work and they said if you nail it,
when the felt expands, it rips, so you should just lay it on, and not
nail/stick it.

Who is right?

Any help greatly appreciated!

Cheers

Ben

"Thanks to God, I am Still an Atheist"

Never, ever, nail felt! This makes holes in it, unsurprisingly. It should be
stuck using the appropriate adhesive which should be laid in stripes up and
down the roof at, say 1 foot intervals. If you plaster the whole roof with
adhesive it is likely that when the felt gets holes in it the rain water
will gather, unable to get out by gravity, whereas with 'vertical' glue the
water, if any penetrates the felt, will run out to the gutter. The you glue
a top sheet on top.

Rob Graham

I've used cheapo felt and good felt, and I'd always use the best if the
money's there. Its a small difference to pay to make the roof last
twice as long.

I've never tried fibreglass resin roofing, but have heard its much
better, might be worth looking into.

NT

The message .com
from contains these words:

've never tried fibreglass resin roofing, but have heard its much
better, might be worth looking into.

Is this something you can buy off the shelf and stick on or do you have
to do a wet lay-up on the roof? I would have thought doing a wet lay-up
on a sloping roof would be awkward to say the least.

--
Roger

Its rigid, so its a wet lay job.

NT

hello ben,
well i'll start by saying that you need to forget about the felt thats
sort of like the vcr compared to dvd
have a new grp roof it lasts forever its not effected by the change in
weather and with the felt you can almost rest assure you'll be paying
out again.
many people are having garage roofs,flat roofs
asbestos roofs replaced with grp roofs.
if you need more advice on where to look for this service contact me

grp has two layers the top layer being a coloured gel coat 100%
water/weather proof.

Hi,

I beg to differ with your above comment.

I understand why you would say this, as old traditional felts could be seen as being the 'VCR' of flat roofing. However, new modern high performance polyester roofing felt membranes are so advanced these days, that most are guaranteed for 20 years but will last for in excess of 30 years at a smaller cost to that of rival materials such as GRP or EPDM (Rubber). These high performance modified membranes are the 'Blue Ray' of flat roofing!

If i can be of any further advise please let me know. I know my view is a bit biased as i work for a roofing felt manufacturer but i have seen a few roofs with all materials on, and i wouldn't be working for who i do if i didn't believe in what i was selling.

Mat Holland