Garage roof advice + ideas of costs

[Mighty Flex]

Hi all,

We have a free standing single garage, 11' by 28' (I believe), and the roof is proving a problem. It has a felt roof that has leaked around the edges, which has been partially removed. Any particularly bad wood at the edges has been attended to, or can be sorted, but the problem lies in the fact that felt has been stuck to the roof with tar rather than being nailed down. Basically, in places it is very difficult to remove, and leaves a mess on the plywood of the roof.
My father has bought a rubber membrane roof covering+ fittings, but we are a bit stuck as to what we can do with it. This could still be returned.

It could be put over the felt, but this seems a bit of a rubbish solution. We could try to remove more of the felt, but this will take a long time - are there any tips on speeding it up, and will the tar damage the membrane?. It could be re-boarded, but this obviously adds a considerable cost. If the plywood was replaced, is OSB worth considering? The beams are not fantastic but are structurally sound.

The other option that has been considered is a pitched roof, but my father hasn't managed to get any quotes out of anyone (though I don't know how hard he has tried ). This is obviously a more expensive option, but ultimately a better solution.

So, what do we do with the roof? What sort of money should a pitched roof be? Are there any other ideas, and how does the cost compare.

I realise I have asked a lot of questions, but it would be great to have some more ideas for what to do, as we are a bit stuck.

Thanks for any replies


Felix

[swiftpete]

Hi, there are two options really, I wouldn't bother trying to take up the felt if it's fully stuck down, you'll never get it up properly. You can either overboard it, or replace the boards completely. If the current boards are chipboard, the best bet is to rip the whole lot up. If they're solid ply, then you can overboard. Use either 11mm OSB if you're overboarding, or 18mm if reboarding.
18mm boards are around £15 inc vat from a timber yard and they'll deliver. They come in 8x4 sheets so for your roof you'll need 10. If you're ripping the roof off you'll need to get rid of the old boards and felt so you can hire a skip. You should be ok with a 4 yarder, if there are loads of stones on there you might prefer a 6 yarder and the price is not too different, plus it should leave you with some room for any other household stuff.
Just make sure you cut the boards cleanly and try and get the surface as flat and smooth as possible.
A pitched roof will cost you a lot more money and you'll need planning permission. It's an option, but if you do the flat roof right then it will last a long time so pitched roof is not really necessary.

Your profile says cornwall/bath, is the roof in one of those places?

[roofer]

Your original roof has been bonded in bitumen. It should of had a venting layer but sounds like it hasn't. The colder bitumen is, the easier it is to strip the felt off. So, first thing in the morning is favorite, get a flat garden spade under an edge and ease it under, you should then find it lifts. If its been done in torch on, it will be bonded in elastomeric bitumen, that will bring the face of the ply with it.
If changing to pitched if the ridge height doesn't exceed 4m then you may not need planning, but check with local authority. Pitched conversion with engineered trusses would be circa 2-2.5k.

If your going to end up buying a new deck, strip existing and deck again.

[Mighty Flex]

Hi

Thanks for the replies. I have just been having a look, but the rain is getting annoying!

This is in Penryn, Cornwall. We are not sure of a good place to order board from if we do decide to do it. Are there any suggestions?


Thanks again


Felix

[roofer]

Look for a Wickes or Asphaltic depot.

[Mighty Flex]

roofer said:

If changing to pitched if the ridge height doesn't exceed 4m then you may not need planning, but check with local authority. Pitched conversion with engineered trusses would be circa 2-2.5k.

Would this be with felt or tiles? Including fitting?

[roofer]

Mighty Flex said:

Would this be with felt or tiles? Including fitting?

Tiles and fitting. Concrete not Clay.

[swiftpete]

Wickes are more expensive than a normal timber yard, their boards are about £25 compared to £15. But they'll still be the same boards, so if you don't have a timber yard close by and don't mind paying more you can certainly use them. Replacing the deck will probably be a better job than overboarding, but it is more work and obviously a lot more mess etc in the garage. It's hard to say what is the best decision for you, but if the current boards are in any way rotten or soft, I'd rip them up. I generally prefer to replace than go over the top anyway, but then I do it all the time so am used to it, if you're doing a DIY job then you might not want to risk falling off one of the joists.
Just make sure you prepare the boards properly and make sure they're screwed down securely before you lay the rubber as you won't have another chance afterwards!

[eskidavies]

corrugated sheets and flashing screwed to existing with screws and rubber washers job done,mine cost 600 quid for 20x15 but i also had galvanised z-perlins and membrane you only need sheets.

[roofer]

eskidavies said:

corrugated sheets and flashing screwed to existing with screws and rubber washers job done,mine cost 600 quid for 20x15 but i also had galvanised z-perlins and membrane you only need sheets.

Probably more suited when there's a bit of pitch about the roof....