porch roof

[nospammer999]

Have a small flat roof over the porch (2m x 1m)... Boarded with t&g & felted over... Its started to leak in one corner ... no rot yet... I was think of reparing with fiberglass mat (csm) & resin + gelcoat.. Should I remove existing felt first? If not how do I prepare surface (brush off dirt & moss & loose chippings & do anything else?) If stripping felt ... can I put new resin & mat directly onto t&g or do I need to cover with something first (thinking of groves in board & also possible movement between boards with heat etc).

thanks AJ

[A.Lee]

I asked a roofer about this a few weeks ago, when a fibre glass resin was recommended on here - his reply was that fibreglass on flat roofs was a waste of time, as it will not expand/contract at the same rate as the roofing material, and would develop cracks eventually, and need to be redone yet again. His recommendation was a torch on bitumen based sheeting, which would last at least 10 years. Not really a DIY option as you need a big gas torch to get it hot enough. Alan.

[chrisj.doran]

Investigate your local DIY shed for flashing tape like

(various widths) which I've found works well. May help to warm it with a hairdryer in this weather. There are also mastics, like this: I haven't tried.

IME, either of these should cover you for a few years until the whole roof needs doing. Inspect carefully while you're up there and consider flashing all the way round anyway, as imperceptible cracks can leak significantly.

Chris

[John Rumm]

Not DIY? Try one of these:

better still:

[tam]

Hi all If you want to fibre glass it you will have to wait till next summer as the air temp must be above 10 c. The method Strip the felt off. Take any damaged/damp t&groove out. I would replace the t&g with WBP plywood 18 mil thick. You can buy fibreglass flashings for about £20 each. These must be fitted first and bonded to the ply with fibreglass bandage. Roofing fibreglass matt should be laid in 1 metre squares-or smaller with 2 inch overlaps on top of previously laid/rollered roofing resin then pour/roller resin on top 1.5 kilos per squre metre. It sets in 20 minutes dry in 24 hours. Then apply wax finish resin for non stick cosmetic finish. Its filthy stinking very hard work but the roof lasts 50 years plus. Its totally waterproof. The resin/hardener is only usable for 10-20 minutes on a hot day so you only mix 2 kilos at a time the secret is to have 10 to 40 pots and throw them away 75p each. The resin comes in 20 kilo drums cost £80 hardener about £15 matt is in 30 metre rolls £100 my Scottish supplier will supply matt cut to size and incomplete drums. All the liquids go off-hygroscopic-so buy fresh. Tam