Just bought and built a 10×10 foot shed. I’m a bit crap at DIY but it’s up, level, painted, square and not going to blow away. Feeling mega chuffed I had the first fix for electricity done on Fri only to find this morning the roof has leaked in the downpour yesterday.

The roof is felted, with 40cm overlaps and little fat nails (tacks?) At 30 cm gaps to hold it down. I assume it’s leaking from one of the mail holes… But need to wait for it to rain again to identify the source of the leak.

Any suggestions for a long term fix? Re-felt? Or sack the felt off and use something else Like EDPM or corrugated metal?

Having sunk a wodge of cash into this already and given its going to be a garden gym with zwift etc I’ll pay to get it dry.

Thanks. I_like_food_but_hate_diy

When ever I’ve felted a roof Ive always stuck it down with bitumen and then nailed it with clouts.

Hasn’t failed me yet. One shed in particular is now 10 years in with the original bnq felt.

That said – my own sheds are all pressed sheet steel and breather membrane

Single sheet of edpm won’t leak and will last as long as the shed. Well worth the money just to remove the faff

Grey Bostic Flexacryl over the nail holes and then ideally on a warm dry day and leave can in a bucket of boiling water before application Isoflex liquid rubber over the whole roof. All from screwfix. Is what I have done and it worked, but it is fixing a bodge in the first place. But I just wanted another 10 years.

If it’s a flat, or nearly flat roof with more than garden tools in I would pay attention to the grade of felt used and how many layers, thin on the bottom and thicker (heavier) on top. The weight of the felt can affect its durability. I would also use felt adhesive (messy) on all overlaps as water can go uphill by capillary action. It’s probably too late now but I would use adhesive under the whole of the base layer. Finding a leak can be impossible, just belt and braces with your methods. Good luck!
Edit – 30cm nail spacing is too wide, more like 30mm?

Did you felt from the bottom up to the ridge?
If not, that could be your problem.

I’ve put a metal roof on mine, but I still painted the sparking/roofing boards with a bitumen paint and flash banding on the ridge to make 100% sure because I live on the inner Hebrides. Felt roofs barely last a winter here. The first heavy rain shower and gale force winds and I was getting leaks through the corners (log cabin with overlapping corners) but the wood has swollen up now, plus I’ve run silicone down the external corners.

Having had a felt roof on my shed and various patches over the years….
Following a thread on here I put a piece of dpm over and then a pond liner.
All good so far.
Gone and done it now……

As above Flexacyrl or Acropol I’ve the nails will work. Your overlap at 40mm is a bit short. Capillary action will go to 50mm, won’t cause leaks but damp is likely

Have you thought of using Onduline (www.onduline.com) corrugated sheets over the felt? They’re easier to use than steel; you can buy a kit from them which includes ridge pieces, just nail straight onto the existing roof, nails with a sealing collar and colour matched. May be worth doing if you want the building to last. Felt is a bit mickey mouse especially if you live somewhere that gets a lot of wind and rain.

Any overlaps should be minimum 150mm, felt from the bottom up no water can run under joints

one piece edpm, cant think of a reason to do anything else

Redid our inherited leaking one with the onduline shed kit (A shaped pitched roof. Seriously easy and quick, looks better and should last ages.

40cm overlaps

Way to short , a light breeze will blow water under that . As said above 150mm is the way to go.

40cm is 400mm, that’s a fair overlap.

Edpm. At least a 25yr lifespan whereas felt you’ll get maybe 5yr. A single sheet will mean no joints. Dea easy to fit as well I.e. no messing with bitumen

The water could be tracking along one of the edges of the roof and getting in that way or could be driving rain.

Check it with a hose to see where it’s getting in.

Thanks all.

Yes, laid bottom to top. 400mm overlaps so that should be ok, but nails every 30cm, not 30mm as suggested. No bitumen, but that sounds minging to work with.

Will check out the corrugated roof but am feeling like EDPM is the way to go… Have lost faith in felt.

Will update when it’s done in case anyone’s interested.

You can retro fit the bitumen (it’s actually a liquid at normal temperature). Gently lift the overlap, use a stiff paintbrush and paint it up underneath as far as you can reach, nice and thick. Settle it all down with a wallpaper seam roller then nail at appropriate distances – usually 30mm but check your felt. I’ve had over 10 years out of correctly fitted felt roof’s, double that with two layer heavy duty. Use latex gloves and have lots of white spirit for clean up! A quick fix that should at least get you through the winter.

Edpm. At least a 25yr lifespan whereas felt you’ll get maybe 5yr.

Nonsense, properly done multi layer built up felt is a longer lasting and more expensive product. Single ply such as EPDM is a cost saving solution generally. I do this for a living.

If OP has only put a single layer of felt on then thats why water is penetrating; it’s supposed to be done in 2 to 3 layers. If it’s 2 layers already then it’s just been done poorly or incorrectly and needs re-done.