Waterproof roofing for shed?

My 12' x 10' garden shed/workshop is leaking - for the umpteenth time. Several times over the last month I've plastered black sticky stuff over the seam where it occurs. But somehow water is still getting in. This is the second felt roof I've had in 12 years and prompts my first question.

Q1. Why aren't shed roofs simply covered with some robust plastic sheeting, cut to size and nailed or glued after tucking around the edges?

I'm not a confident DIYer so want to get someone to fix it. But so far all the companies I've been looking up online seem to describe 'felt' in the context of sheds and flat roofs.

Q2. How/where can I find someone or some company to quickly cover the existing old felt roof (slightly sloping) with a permanent, reliable waterproof sheet of some sort, whether plastic, rubber or whatever?

Q3. Are there any downsides to such an approach please.

I need to get something done urgently, as the shed is used for my electronics hobby. Latest project damaged overnight.

Any practical advice would be much appreciated please.

Reply to
Terry Pinnell
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Reply to
Andy Burns

Wrong time of the year unfortunately as it must be applied in the dry but fibreglass would solve the problem very well. Butyl rubber (as used in pond liners) is an alternative that isn't as good but will last much longer than felt and doesn't need warm dry days to apply it.

Another alternative is clear Polycarbonate sheet. This is normally used to replace the roof (and give lots more light) but can also be laid on top of the existing roof.

Many roofers only understand hot melt/felt especially for sheds and although the techniques for all are fairly simple they often get it wrong. Find a local roofer familiar with the material you want to use

- for fibreglass and Butyl Rubber suppliers may be able to help with contact details for roofers who use their products.

Experience in Polycarbonate sheet is more usually found in local double glazing/conservatory companies but you might want to consider it (replacing the whole roof which is quite easy) as it transforms the amount of light inside.

Reply to
Peter Parry

But might not survive in full sunlight or with the odd tree bits falling on it.

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Reply to
charles

Yes someone I used to know swore that Butyl or however its spelled was the answer to this. Its often used in ponds, apparently.

I have a little shed that probably could do with a new roof. In the old days they used to use corrugated asbestos of course.... Brian

Reply to
Brian-Gaff

The brown corrugated roofing panels may be what you need. They can often be fixed over the top of everything. Several brand names, I think 'Onduline' is one, but bituminous fibrous shed panels. wickes have them.

Tim W

Reply to
Tim w

Appreciate that there is a wide differences between different "qualities" of felt roof...

You basic thin "shed" felt applied as a single layer and nailed on, its unlikely to offer more than a few years of reliable service (if at all).

Whereas a hessian re-enforced 2mm thick SBR[1] nail prep sheet glued or nailed on, then covered with 2mm SBR under felt, and finally finished with a 4mm thick SBR cap sheet with mineral finish will last decades as long as the substrate its fixed to is decent and stable.

[1] One of a number of trade names for a bitumen material modified with synthetic rubber or latex compounds to make it tougher and more flexible with age. Often available as "torch on" felts which are highly effective and very quick and easy to apply.
Reply to
John Rumm

If you want a rapid fix, just another layer of felt will do it. Easily diyed.

NT

Reply to
tabbypurr

Must say I'm attracted by the potential for replacing my many mains lights by daylight. But presumably I could no longer stand on it as I can at present, to cut back the adjoining laurel?

Reply to
Terry Pinnell

Thanks Tim, that looks promising. Just watched this video by Peter Parfitt:

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Surprised that none of the roofers I've spoken to ever mentioned it. Maybe half a dozen five years or so ago, and four this morning, with more calls yet to make.

Reply to
Terry Pinnell

It must have been very badly done to only last 6 years. Even a poor felt roof should last 20 or so - especially on a shed with presumably a pitched roof.

Reply to
Dave Plowman (News)

Thanks John. The only local man I've chosen so far to visit for a quote sounded enthusiastic about the 'torch on' felt. He also raised the alternative of rubber sheeting. I'll ask him about Onduline (or Wicke's equivalent) when he comes.

Although speaking from the depths of ignorance, I'd have thought that any method that did NOT involve seams and nails had a head start? Surely nails (or screws) are potential leak points, apart from the extra labour. After my latest inspection, I'm fairly sure that's where my current leaks are coming through.

Also, is there no spray-on stuff that dries over the top of the existing roof to a tough waterproof finish. A sort of industrial equivalent to these tins of paint-on covering I've been buying from Homebase?

Reply to
Terry Pinnell

You could always put a plank walkway on it if you used triwall. That would be quite adequate to spread your weight and walk on to trim the shrub and would cost you too much light.

Reply to
Peter Parry

Well if you are going to use nails you use them to fix the first layer only. A so called "nail prep" layer. This is a felt with hessian or similar fibres in it that make it much harder to pull the nails through. You fix that down with clout nails using a random pattern all over. Then you torch the underlay directly onto that. Once that is on there are no

*visible* nails.

You normally run of felt across the roof. starting from the bottom of the slope at the eves, and work up. The next strip overlaps the previous by abut 4" to 6" and directs any water over the previous strip. The top strip needs to saddle the ridge such that it covers the top of the strips of felt on both sides. (there are times where you can run an underlay perpendicular to the final layer).

When you fix the cap sheet you arrange for the overlap to be in a different place from the layer below. The cap sheet also has one "sticky" edge about 4" wide on the mineral finish side, That means that the two layers actively bond to each other at the join.

Have a look at:

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for an example of use.

Indeed - if the nails penetrate from the surface they can be leak points. Having them just fix an undersheet however avoids that.

You could just stick a torch on cap sheet over the lot.

Reply to
John Rumm

Wickes sheeting is Onduline, IIRC from reading their website recently.

As someone else said, they often just seem to think about torch on felt cos that's what they know.

I would consider the noise though if you will be in there in the rain. I don't know how Onduline is as it's quite a bit thixker than plastic sheeting, but corrugated plastic, or the double/triple wall stuff is really noisy in the rain

Reply to
Chris French

Get about that on our felted shed roof. But that's using "shed roof felt" which is very lightweight compared to proper roofing felt.

Reply to
Dave Liquorice

Might be but I wouldn't bank on it. Hot dipped galvanised clouts have farly large diameter shanks and a big flat head. The bitumen displaced by the shanks is compressed back around the shank by the head, in effect they are self sealing. But is the spacing is too wide and or movement the flet can fatigue and fail around the head of the nail.

Reply to
Dave Liquorice

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