Plastic roofing underlay with adhesive

radioactiveman

Hi,
Does anybody know where you can get plastic underlay for roofing that has adhesive on the back?

The type I am looking for is like normal underlay but with glue on the back that can be heated with a blowtorch to put it on. I have seen it around but can't find it anywhere in hardware shops
(background to this is my garage is leaking with joists actually going rotten + with woodworm because they are completely wet... so would like to do a good job while I'm at it).

thanks!

Buford T Justice

radioactiveman wrote: »

Hi,
Does anybody know where you can get plastic underlay for roofing that has adhesive on the back?

The type I am looking for is like normal underlay but with glue on the back that can be heated with a blowtorch to put it on. I have seen it around but can't find it anywhere in hardware shops
(background to this is my garage is leaking with joists actually going rotten + with woodworm because they are completely wet... so would like to do a good job while I'm at it).

thanks!

If you're joists are rotten then you need to replace them. What is the roof currently made of?

Can you post up a pic?

North West

Hi radioactiveman
I think what you might be looking for is torch on underlay ( it's not plastic but it's very tough ) Usual roof 2 layers of torch on underlay and 1 layer of torch on overlay. It's available in most builder merchants. Then you can buy a silver paint to reflect sunlight in summer ( dont know the name of it ) Be careful when torching felt.
North West

radioactiveman

Hi NorthWest
thanks that sounds like the stuff, will know what to ask for

If you're joists are rotten then you need to replace them. What is the roof currently made of?

Can you post up a pic?

Will put up a pic in a while
It's pretty bad. The garage is a basic block building with sheets of galvanised iron for the roof.
Where the galvanised iron meets the wall it goes into the concrete, but there are 1 or 2 fairly big gaps (an inch or two) where the water is getting in. When the roof was first done I think the felt inside actually kept out some of the water, which wasn't a great solution :pac:

I am thinking of:
taking off the galvanised iron sheets,
replace the joists that have gone bad
put on roofing grade MDF, then underlay, then felt

- Maybe also put in lead, the garage wall is higher than the actual level of the roof so it might be possible to cut a slit in the wall, put in the lead flashing and then seal it with some concrete, but I haven't done it before so I've no idea if that would be a good solution

Forgot to mention: a little water getting in isn't the end of the world but you can see the cavity blocks are soaking wet where it's happening and one of them has actually cracked inside and out

radioactiveman

Pic:


water is getting in at the left of the picture where the wall is higher than the roof. It looks ok at this angle but further in there are gaps. Where the roof is going into the concrete in the middle it's basically ok though

Buford T Justice

Are you looking at re-doing the whole roof, or just repairing the damage at the front?

Would definitely be no harm in cutting a trench in the wall and dressing in some lead to keep the water out.

North West

Hi Radioactiveman

If your thinking of replaing the roof check timbers are ok and are at suitable centres on roof. Use OSB 18mm or Shuttering ply. Then torch on underlay felt, the torch on overlay. take off capping on wall and you can torch up and over the blockwork. Then replace with new capping.

North West

endasmail

id use WBP plywood 18mm
id also go with lead flashing down the wall ,with the trench cut into it