Using a breathable membrane under tiles

Lemo

My shed has a tiled roof with no felt underneath and is leaking in a few places. The pitch is quite shallow so it's probably windblown rain. A friend got me some Ruberoid Roofguard SB to put underneath. My question is what to use with:

- Normal clout nails for that you'd use for felt?

- What sort of adhesive, if any on the horizontal laps? I'll be able to put decent-sized laps, 250mm or so.

Thanks.

Viking House

The clout nails are fine, don't pull the membrane tight, let it sag between the rafters, no need to use adhesive where the membrane overlaps as this helps the roof to breathe, unless the pitch is bad then you need to tape it.

Lemo

Thanks. I think I'll need the tape. I presume that's something you'd be more likely to get in a builders providers than Woodies etc. What's it called?

Maud

The easiest tape to get may be the one used for a Radon barrier

rooferPete

Hi,

If your roof has such a low pitch that you expect to need both a jointing tape for the underlay and a 250 mm head lap will most likely still cause problems after you fit the underlay.

By using such a long head lap you will be tilting the tiles back which at best will leave them level but most likely the water will be running back with the front lifted off the course below it.

A Major Item to take into consideration is the safety of your roof, if the pitch is as low as you indicate it will mean the tiles are a "Dead Load" on the rafters instead of hanging from the laths.

Concrete roof tiles weigh on average 5 tonnes per thousand, take care about the amount of weight you have over your head and the ability of the timbers to carry both the tiles and items such as wind, snow load etc.

.

Lemo

You might be right, Pete. Maybe I should just take the tiles off altogether and put a felt roof on.

ircoha

Lemo wrote:

You might be right, Pete. Maybe I should just take the tiles off altogether and put a felt roof on.

load a few pics up before u do that, and let us have a peep

rooferPete

Hi Lemo,

You might think about metal sheeting depending on the location of the shed it seems to be a good candidate considering the amount of timber used for a cut roof.

Strip, felt, cross lath and fit the sheets the reason I mention location is you might want a nice to look at finish, tile sheet would work but is harder to fit properly, you can go cheaper with a cladding sheet if you don't mind the industrial look.

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Lemo

OK. Taken in the fading light but should give you the idea... Next door's adjoining shed has a recently done felt roff (same pitch etc.) so it might be easiest to just continue that on.

rooferPete

Hi Lemo,

Hard to work out the pitch from the photos, one possible sign is the top corner in the second photo the tile appears to be flat / level.

The inside photo suggests old tiles possibly 18" x 9" the brand name escapes me at the moment but originally made in Clondalkin, the side laps appear to have been sealed maybe it's a shadow.

If they are what I think and you can remove them clean they do have a re-sale value for repairs.

I agree follow your neighbours roof, if possible use a 50 mm angle fillet under their felt and use it as the joining divide line, that way if either roof leaks in the future the water can't pass the party wall into your deck.

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