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Shed roof replacement advice

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Afternoon all, current shed has been in place for five and half years. Patched a leak on the felt roof last year but there is now more water coming in so I suspect the felt has reached the end of its life. Roof is 3.5m and it's just under 5m long.

Current setup is sarking boards which I think are still sound. I was going to put OSB over this and either get 10/15 year rated felt or go down the EPDM route. 

Having picked up some 18mm OSB yesterday off marketplace I am now thinking it might be too heavy to add onto the existing structure and that 9 or 11mm would be better.

If I stripped the existing boards off I would need to recycle these and I'm not sure the EPDM works ok when it's not on ply or OSB. 

Also, with EPDM do you have to use the trims? The adhesive element I understand but the trims are confusing me at the moment.

Any advice?

 


 
Posted : 11/06/2026 2:44 pm
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I am not sure about the EPDM side of things. I looked into it briefly when re-doing my shed roof.

In the end, I went with Coroline boards. I think another brand is Onduline. They are easy to handle, durable, easy to cut and you can get ridge tiles which makes it pretty easy to do a neat job. It would be worth looking into that option.

18mm OSB does seem a bit over the top for a shed roof 😁


 
Posted : 11/06/2026 3:23 pm
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Posted by: stumpy01

18mm OSB does seem a bit over the top for a shed roof 😁

I used that on mine, on 6" rafters. But it's a turf roof I can grow strawberries on and walk around on for weeding/picking


 
Posted : 11/06/2026 3:50 pm
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I've put EPDM on two garage roofs and one porch roof in the last 10 years, all have been problem free. Easy as anything to do. Technically uses a trim but I don't see why it wouldn't work just folded under itself at the edges.


 
Posted : 11/06/2026 4:30 pm
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EDPM is my go to such roofs. So easy to use.

Generally I "improve" the detail on the standard ex-factory roof edge, adding fascia, barge boards and drip battens all round. On the pic below, I used the contact adhesive round the perimeter and onto the vertical edges. Trim rubber edge with a new Stanley blade against a extra spacer strip after gluing. 

Not 100% successful tbh, a year or two later the rubber is peeling off a bit on the edges. I think stumping up for the proper edge trims is the way to go.

IMG_20240831_173943052_MFNR.jpg


 
Posted : 11/06/2026 4:55 pm
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I also went the wriggly plastic sheet/ onduline / coroline route on my old shed. Been there 12 years and never an issue.

(And my newer two sheds have been plastic Keter sheds for this reason...)


 
Posted : 11/06/2026 5:00 pm
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I've got EPDM on my shed roof.

It's glued onto ~150mm 19mm T&G boards.

At the gutter edges it came with it's own trim pieces, which I f***ed up fitting by cutting the EPDM to the wrong line so they don't grip it properly, so it's actually just overlapping a bit and not doing much.  I don't really see why, other than neatness, you couldn't just use nails like you would felt.  I suspect the reason is simply that the plastic trim will last 10-15 years whereas nails and wood wouldn't.  The Gable end is just finished with wooden boards. 

Fitting was dead easy, drape it over the roof to get it in the right position, peel back half of it and apply adhesive, roll it back and press it down.  Repeat the other side, trim off the excess and fit the trim pieces.  Unlike felt on the other shed which every time you touch it tries to fall apart a little more. 


 
Posted : 11/06/2026 5:09 pm
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I just went with glued down felt again, but it's definitely got downsides, pain in the arse to work with and depressingly easy to damage. I do like the look though. 

Way I see it is sheds are an impermanent structure, I'm reroofing mine because I just moved house with it frinstance, if it's still in the same place with the same roof and in good shape in a decade I won't mind putting a new roof on it if it needs it, but there's a pretty good chance it won't be and so doing it cheaply and easily and impermanently makes sense to me. 


 
Posted : 11/06/2026 5:11 pm
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I did my big shed with Coroline corrugated sheets about 15 years ago, it's gone out of shape badly and is very leaky now.


 
Posted : 11/06/2026 5:36 pm
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Posted by: Simon

I did my big shed with Coroline corrugated sheets about 15 years ago, it's gone out of shape badly and is very leaky now.

Is that the sheeting that has failed or the structure underneath?

Coropol about £360 with ridge trim and screw fixings.

EPDM about £180 for the rubber then adhesives maybe £60-£100) trim bumps it up a fair bit. 

Felt probably £130 for 20m of decent stuff and some adhesive, I have nails already.

 


 
Posted : 11/06/2026 7:03 pm
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Just added metal profiled 2nd hand sheets to my roof, but it does have good 'trussed' for support. If using flexible type sheets they need uniform support as they can loose shape in hot sun. Felt just does not seem to last these days!


 
Posted : 11/06/2026 7:13 pm
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@rockthreegozy It's the sheets that have failed, they're supported on purlins, I think the spacing is to spec.

 


 
Posted : 11/06/2026 8:48 pm
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Metal profile ‘tin’ roof on mine - survived the 90mph winds of Storm Amy


 
Posted : 11/06/2026 9:52 pm