leaking flat gararge roof questions

[wosun008]

Hi

My garage has a metal roof leaks eveywhere, it's a 6.5 by 5.5 metres sigle biulding. There are only four 5.5 metres wood beams and I can see mushroom on them, so think I need a whole new roof, joists deck boards waterproof layer....

I've done a lot of search and am confused about felt GRP and EPDM
felt won't last long time
GRP cracks and it's too cold now
EPDM needs adhesive and there is a fox family around, have no idea if they dig this, they dig a few holes in my garden

Some roofer told me 4 joists are not strong enough, should be 9 so the spacing between joists will be 600mm(now it's 1.2m) and they can biuld the GRP roof,
Is this necessary for all kind roof or only for GRP, what size joists do I need? how about the deck boards? plywood or OSB3? what thickness is needed?

I prefer EPDM but still havn't make my decision. please give me a rough price I should expect to pay, felt GRP or EPM whatever you say may help

Thanks

 

[freddiemercurystwin]

We assume the joists can span the 5.5m width so they ought to be something like 63x220 joists @ 450 centres. Decking can be OSB or ply although ply would be my choice, 18m thick whichever you choose. Personally I do not believe there is much difference between any of the flat roof materials including felt, they will all last well if constructed well, workmanship is the key to a long lasting roof.

 

[wosun008]

Why you choose ply? is it better than osb3?
what's the difference betteen torch on felt from bitumen Adhesive felt? which is better?

 

[tone1967]

for doing a garage roof 18mm OSB would be just as good and cheaper i would have thaught ?

 

[freddiemercurystwin]

OSB will be cheaper and will work I just don't like it tis all it can delaminate and fall apart.

 

[tone1967]

so it just comes down to a personal choice ....

as for the felt go for Torch on but don't go for the cheapest you can find

 

[wosun008]

I checked the old joists, they are 50x200 not 63mm
one roofer told me the roof needs 18 50x200 joists, are there too many?

are exterior (WBP) Plywood boards softwood ply boards or hardwood ply boards?

 

[cotswoldbuilders]

18mm t&g osb roof board or ply, with epdm rubber cut to size.

 

[freddiemercurystwin]

Joist predictions from your roofer sound about right to me, the smaller they are the more you need. I suggested you went for 63x220 @ 450 centres he's gone for smaller joists at smaller centres to compensate.

 

[catlad]

OSB.3 is made for the job, I think freddy you are thinking about the old stuff that did fall apart when it got wet.

 

[Zeberdee]

EPDM adheared to OSB3 (better in my opinion than ply cuz it dont de-laminate.)

And I dunno what the O.P. is going on about with foxes????

It must be another very poor rumour started by a worried felter or GRP fitter lol.

I've heard rumours that birds peck the rubber EPDM!!!! lol And that squiralls (sp) scratch it!!!!!! pmsl

 

[Xenon]

Hi



felt won't last long time

If you buy it from B and Q , no, it won't. If you use proper felt, then it will outlast most things. 600 centres with 8x2 will be fine on 18mm OSB