Plastic liner between joists and roof tiles - what is it?

[nickldn]

I wonder if someone can help me identify what type of plastic liner I have between my roof joists and roof tiles, in the loft.

My house was built in 1968 with a pitched slate roof, there's a flexible black plastic type lining between the slates and the joists supporting the roof, but it's started to rip in places exposing the slates, which in turn seems to bring in damp to the ceiling underneath the loft.

I need to buy some replacement plastic sheeting to patch over the holes/tears, buy I don't know exactly what I need. I've spoken to a few roof merchants, but they haven't been particularly helpful.

Could anyone offer me any advice?

Thank you in advance,

Nick

 

[freddiemercurystwin]

The purpose of the lining you describe is really as a back-up in extremes of weather. If the slates are leaking they probably need replacing so could be a sign your roof is nearing the end of its life, or maybe they were laid with inadequate gauge (how much they overlap each other) when first fitted. Millions of houses across Britain have no membrane at all and their roofs do not leak.

Is this the original roof? Would have just expected felt membrane.

Photo?

Anyway try here //search.diynot.com/forum_sear...tbytime=0&author=&search=Search+Forum&stype=0

 

[nickldn]

Thank you, I think I've found something suitable:

Cromar VENT3® Light

I've found a 15m roll for sale, which will be much cheaper than buying a while 50m roll. Will it be ok to use this product to patch up the current membrane?

I don't think there's a problem with the roof itself, rather its lack of ventilation causing mould around the ceiling edges of the bedroom and bathroom, but it seems to be worse in the places where the current membrane is broken. I know this won't solve the problem entirely but it may help alleviate it little.

 

[catlad]

Sounds like you have a membrane that was around in the 80's that was basically plastic and was discontinued due to condensation problems.

 

[nickldn]

Could anyone give me some idea of difficult would it be to replace the whole membrane.

It's an end of terrace house with a pitched roof which is sloped on the end. This means the membrane would need to be changed on three sides of the house, in a cramped space. Would tiles need to be lifted to slide the membrane between the joists and the tiles?

I could probably attempt it myself, it it doesn't involve lifting tiles, but it's going to be a tough job.

Would replacing the old membrane with a breadthable modern type really make a huge amount of difference to the levels of condensation in the house? The roof eves should let moisture out, but I don't know for sure if they let out enough.

 

[freddiemercurystwin]

It is impossible to replace a roof membrane. and when I say impossible its not a bit difficult its actually impossible. Unless you remove all of the tiles and their battens first.

On a roof, the membrane is sat on top of the rafters. Then the battens are fixed, with nails, to the rafters, through the membrane, then the tiles hung on the battens. So without removing all of the tiles and removing all of the battens that are nailed to the rafters it is impossible to replace the membrane.

Unless you are Mr Impossible that is, he's one of the Mr Men. I know this because I've just read it to my lad. Mr Impossible could do it but not you. Sorry.

Does your house suffer from excessive condensation then?

 

[nickldn]

I thought that might be the case somehow, well I guess I'm stuck with it, unless I do a loft conversion and even that probably won't help.

The house is fine, until it gets cold, then mould appears on the 1st floor ceilings predominantly in the two outside corners of the house, at the end of the terrace. It just so happens the roof membrane is torn near those parts, so I was thinking there might be some correlation. But I suppose it's more likely it's to do with double glazing and lack of air circulation.