Making shed roof waterproof?

What is wrong with the roofing felt which everyone uses for sheds?

Just lay it from the roof lower edge working up to the peak, with a good overlap for each layer, nailed down with the galv headed nails made for the job at least every 9" or so. When both side are finished, have one side overlap to the other, or lay a final strip along the peak.

Done properly with decent felt it will last for years. Leave the old felt in place for extra waterproofing.

I wouldn't use nails, I'd use roofing bitumen to stick it down.

Felt sold as suitable for sheds is generally fairly thin rubbish and does not last for very long.

The heavy grades fare somewhat better.

The key point is to avoid having any exposed nail heads at all.

This can be achieved by cutting the top strip on each side so that the top is about 100-200mm down from the apex on each side.

It is also a good idea to paint some compatible adhesive/sealer below and above the top of each level of felt as it is laid.

Finally, a strip can be cut to go over the apex and overlap the top level of felt on each side. This can be stuck down with sealer and no nails at all.

At the bottoms, a small batten should be fitted underneath the roof boards. The felt should be folded over the batten and then it can be nailed to the underside. The point is not to have any nails exposed directly to rain or water running down.

Indeed. I simply got new felt, new battens, and spent a merry day in the summer re-felting mine. no leaks.

Thanks all - but I asked about plastic (or alternatives). I have felt at present - and it leaks! Key phrase in my post was "...a permanent solution".

Nothing's permanent. Felt should last a long time. If that's not long enough, why not use slates?

I would expect the proper grade of 1mm stainless steel sheet, properly fixed down at the edges to last several centuries. A meter thick slab of granite should last much, much longer, though you need to check to see if the existing roof will cope with the load.

Hey, not so fast, my slates are 100 years old and one or two have slipped.

Perhaps the OP is planning to store nuclear waste.

Jim A

Felt is the alternative to plastic. Done properly, as instructed, with good quality materials, it will last for years.

MBQ

Define permanent.

MBQ

On Mon, 03 Apr 2006 16:13:07 +0100 someone who may be Terry Pinnell wrote this:-

How will plastic not leak?

Felt is not permanent, but I doubt if your shed is either. Felt should last 5-10 years without leaking, if done properly.

Some types of plastic are vulnerable to the sun.

Have you still got the guarantee?

I wonder how long roofs on new houses will last....

Put it in an enamelled steel bread bin, cross out the word "Bread" and write in "Nuclear Waste" in red felt-tip.

Tile it. After rebuilding the roof and walls to take the weight.

There is no permanent solution. Very few Neolithic roofs survive intact. Possibly you could make a 'long barrow' and use sarsens covered in earth ;-)

Or lead, or copper.

Bad felt will last about 5-8 years, good felt will do about 20.

All are, to a greater or lesser extent.

A lead roof is the answer in that case, reduces the rays.

On Tue, 04 Apr 2006 14:43:34 +0100 someone who may be wrote this:-

A suitably thick roof would be rather too much for the wooden walls, though they and the floor would need to have lead added to them as well. The door would be interesting.

Still not permanent though:-)