insulating a solid wall

[oldfart]

hi all, can anyone help,

Had a two storey extension shell built (over garage), the main side wall to the extension has come straight up off the garage wall which is 4" block with facing brick (no cavity).

In order to comply with reqs plans show the following spec,

Breather membrane to blockwork, 3x2 studding, 75mm dritherm, foil back plaster board.

I understand the principal of it however the breather membrane is causing me a few probs.

I can only find the stuff reccommended for roofing, is this ok?

If so I only need about 10mts yet some of the rolls seem to be 50mts and cost hundreds! is there a smaller product out there i cant find one.

Once i get my hands on the right membrane i,ve got to fix it to the blockwork any ideas on the best way of doing this

many thanks

 

[Mr Winston]

When i first read your post i thought you had built a 4" block wall 2 storeys high!

I think you must have some steel beam or similar to carry a cavity wall for the first storey, am i correct?

Are you having a clear 50mm cavity between the studwall and the existing blockwork - or is the studwork going to butt against the block wall with the insulation between the studs?

If the latter I think you should be looking for a vertical DPM to the 4" block wall - rather than a breather membrane (which is more like a timber frame construction)

Dupont Tyvek do house wrap breather membranes for timber frame construction (reflex i think & hence the length and price as its normally used for new houses) - this is different to the roof breatheable membranes.

To get any shorter lengths you may want to look out for timberframe house going up in your area who may have 10m+ offcuts from their jobs

The membrane is fixed to the studs not the blockwork

 

[oldfart]

Thanks Mr winston sorry to have scared ya with the blockwork!, you are correct regarding steels!

You are also correct when you assume the 3x2 is to butt upto the blockwork, and infilled with 75mm insulation, i agree with you about the vertical dpc, rather than membrane. in truth its not really a solid wall there is a slight cavity between block and brick about 30 - 40mm.

After posting the thread yesterday i phoned my labc to convince them i didnt need membrane, They agreed! however they then sadistically burst my bubble when they said if the architect has specified it on the plans then i must abide!

On my travels yesterday i popped into a Travis Perkins who were very helpful had,nt come across my prob before but i left there with a roll of breather membrane (£90.00)

thanks for your advice though, you say fix the membrane to the stud, I assume build the framework on the deck staple to the back? offer upto wall & fix.

thanks again for replying