Garden Shed Roof

[JoeJoe]

Our shed has a single layer of felt on its sloped roof nailed in place with battens nailed over along the edges. The shed is free-standing.

It has now developed a leak.

My plan is to recover it with new felt - preferably two layers (or more

- as many as I can get out of the role).

I may be missing a trick, but I cannot see any roofing felt on Screwfix's website. All I see are underlay felt. Is that the same thing?

Alternatively, corrugated plastic sheets seem to be pretty cheap, so it got me thinking... What would using those instead involve? I see that I will need screws (as in

or similar). But, what would stop the water from running down the underside of the sheet though? Would I need one of these as well?

TIA.

[Bill Wright]

Buy from a roofing supplier.

Bill

[Brian Reay]

I would use felt, a couple of layers, using 'lap cement' (a rubber like glue) to bond the layers together. Be generous with the cement. I did a couple of dormers like this in our previous house over 20 years back. As far as I can see the front one at least is still in place.

[Bill]

In message , JoeJoe writes

Often recommended here, what I used was Onduline corrugated sheet. I think cost-effectiveness depends on how the length of the sheets matches the width of the roof. On mine each single sheet matched the roof pretty well, so there was hardly any wastage.

The apex of the roof can be covered with the special capping pieces.

I used stainless screws and plastic washers through the tops of the corrugations, not the nails suggested in the literature.

No messy black gunge needed, easily done on my own, and it is lasting very well.

[newshound]

If you eBay "steel roof cladding" you may be surprised how cheap the plastic coated or galvanised stuff is. For a single pitch felted roof that might be the simplest way to do something which will out-live any standard shed. With the type which is basically flat with little ridges, you could just glue it down using mastic straight on top of the existing felt. I'd put a few screws with penny washers along the edges to prevent wind lifting. You can put these in the valleys as long as there is a good splodge of mastic between the sheet and the felt, it won't leak then.

[JoeJoe]

Thanks for the tip - looks good.

Problem is that my roof is sloped, not pitched. How would I stop water from running down the underside of the sheet from the higher end of the roof?

[Bill]

In message , JoeJoe writes

I'm not sure, but I would have thought that either the ridge or the verge shapes would have worked OK just with the free side hanging over the edge. My sheet edges just hang over the edge of the existing roof by about 3" and have survived fine, so I don't think the unsupported edges would come to much harm in high wind.

[John Rumm]

Much the same way - with a capping that protects the edge and allow water to drip off the top. kind of like you are creating a mini ridge.

(alternatively you could flash right over and onto the wall at the top)

[Brian Gaff]

Do not use corrugated plastic sheets. Worst thing since non sliced bread. Go brittle and crack then torn off by wind. Brian

[Brian Gaff]

And use galvanised nails. Brian

[Nightjar]

Most standard roofing sheets have a wall flashing available to match their profile.

BTW, if you are laying onto a solid roof, check that the sheeting you are using is suitable for that application. Some specifically state that they should not be used on a solid base.

[Harry Bloomfield]

I agree. I used the metal sheet on my garage with a 6" over hang at the front and it faces into the weather, with a down slope to the rear. I have never had any issues with water running along the underside of the sheets, or the sheets being caught by the wind. I did make a point of adding plenty of fixings along the leading edge though.

[stuart noble]

Last time I looked Homebase were the cheapest for bog standard felt. Keep it simple I reckon

[Dave Liquorice]

Did our shed with the small corrogations "Onduline" a while back having got fed up with felt only lasting 5 years or so.

Width? That to me is left to right not up and down the sheets go on up and down... Even with cutting 2' or so off each sheet it's still worth while IMHO. I don't expect to have to do it again so saving the time and cost of replaceing the felt again... I also have uses for those offcuts, old galvanised tank cover and something to go over the genset when it's earning it's crust outside in the weather (which is likely to be bad if it's running)...

I used the nails. Did it about 2 years ago, looks like it as done yesterday and survived Ophelia (we had gusts into the 60's mph and sustained windspeeds of over 50 mph).

[Thomas Prufer]

You'd want a felt that has crushed slate on the top, or some other UV protection. Underlay felt may not have UV protection.

Onduline is ok and very cheap, and will last > 10 years if you don't step on it when it's cold and stiff. Metal panels can be loud when rain falls on it.

I'd put Onduline or metal panels over the existing layer of felt...

I have heard on usenet that pond liner makes a reasonably priced roof, and comes in sizes that make one seamless piece feasible even for large sheds. The people suggesting this say no UV protection needed, other disagree.

Thomas Prufer

[Bill Wright]

I did a roof with that stuff and it's been fine. It was an easy job as well.

The B & Q stuff is thinner than some others. Don't use it.

Bill

[Andy Burns]

Coroline is thinner than onduline, but there's not much in it (2.6mm vs

3.0mm)

That said, I did intend to use onduline, and ordered some online because I could only find coroline in wickes and B&Q, only to discover after cutting it to length that what had been supplied *was* coroline (I got a refund for the difference) it's been fine for over 5 years, one pressure washing to remove algae that gathers on it because it's under a tree.

[JoeJoe]

Unfortunately my roof is 2.1m long (top to bottom, slopped roof), and the sheets come in 2m, so going to be a messy job...

[Bill Wright]

I had a similar problem. I can't remember just how I did it but by making each run of 4.2m from three pieces I was able to use almost all the sheeting. I don't think the three pieces were equal. I'll have a look in a bit. I do think it's a good idea to allow a lot of overlap by the way, especially if the slope is slight.

Bill

[Martin Brown]

This time of year you might be better off patching it with a temporary repair and waiting for a nice dry sunny spell to do a proper job.

Various bitumen paints and black sealant gunges in tubes are available for this sort of thing. Wear clothes you intend to throw away after.