Garden office roof replacement

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16 Oct 2009
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Location
Gloucestershire
Country
United Kingdom
Hello,
I built my 4x3m pent roofed garden office (shed) about 20 years ago and the 3 ply felt roof has just about given up on me. I'm looking to replace it and am seeking some advice about my options.

Felt
I could simply strip the felt and apply new. I know that the substrate (18mm OSB) will probably be sound and all the edges/trim would be reusable. It's the cheap option but would fail again in 10-15 years just as the last one has.

EPDM
I'm interested in this option as it seems to be the next cheapest and has a longer life expectancy (50 years?). I don't know if the existing substrate will be 'clean' enough for this option (tar spots, divots, protruding OSB edges, etc.) and may need replacing. That's bump the cost up and I don't know if 8'x4' boarding or T&G boards would be better. I'd also be interested in adding a layer of insulation if going with this option to help reduce the heat in the summer (don't know why I wouldn't do this with a felt roof too) and to deaden the noise of rain. Would that require an additional boarding over the top? Is it actually going to make any difference as the walls are not insulated?

Metal sheeting
This too has a longer life expectancy but seems to be susceptible to condensation and noise. I'm also not sure about how to finish any cut ends to avoid corrosion.

Insulated metal sheeting
A more expensive version of the previous option but with improved condensation and noise management. The same problem exists regarding exposed cuts.

GRP
Seems a bit fiddly but I have worked with glass before and so it is viable. I don't know if this is overkill for a garden office/glorified shed.

Tile
The fall is only about 10% so tiling is an option but it's on the limits and is probably a pricier option. It's require a lot more prep but would be more durable.

I think I'm leaning toward the EPDM option but would like to know how 'clean' the board needs to be to lay it on and what, if any, insulation options I have to reduce the noise and heat issues.

Any tips appreciated,

Mike
 
You could just overboard it with another layer of OSB. But if going to that expense then the insulation might not be a terrible idea, you use something economical and sandwich it between the layers. Then your EPDM on top.

If you can find insulation seconds, or find a builders merchant with a special offer on, then insulating won't be too much extra.

Some would poo poo the idea, as the walls aren't insulated. But if you have any form of heating in there, then that's good enough reason, plus it future proofs it if you wanted to insulate the walls in the future. (Boomerang kids, wife kicks you out etc.etc)

https://www.secondsandco.co.uk/

Insulated metal sheets are also a good option, you can spray any cuts end with galv spray, it will get covered up by the angle trim anyway.
 

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