Brick & Block Airtightness

[AD1]

Hi all, 

 

I'm about to start my build, standard clay facing brick, 150mm cavity with wool batts and inner block. Floor construction is block and beam, 150mm PIR and 75mm screed with UFH. 

 

My questions are around achieving airtightness. We are installing MVHR and so want to get it right. My architect has specified plasterboard on dabs to block walls but after reading on the forum some have used 25mm battens to create a service void and fix boards to.

 

- Should I put a breathable membrane  onto the blockwork then batten? It's going to be plastered and so is this overkill? 

- Another option is a parge coat? Which is better for airtightness? 

- Most walls on the groundfloor are block, should I use a membrance on all walls or only the external walls? 

- If I use a membrane, what's the best method to fix it to the block before battening? 

- Any recommendations on product brands etc? 

 

Thanks, 

 

Adam

[nod]

Yes you can achieve good airtightness  on brick and block The block work needs to be pointed properly and the dot and dab needs to be solid lines around every angle and sockets etc 

Parge is a waste of time and money 

Great for soundproofing But encourages the dry liners not to do there job properly 

 

[Miek]

Or wet plaster the walls instead of plaster board.

 

Care and attention with regards to the floor joists or any wall penetration is important. How is the first floor (if any) built?

 

 

 

 

[AD1]

46 minutes ago, Miek said:

Or wet plaster the walls instead of plaster board.

 

Care and attention with regards to the floor joists or any wall penetration is important. How is the first floor (if any) built?

 

 

 

 

 

First floor is eco-joists on hangers with stud walls above. 

 

[nod]

1 hour ago, AD1 said:

 

First floor is eco-joists on hangers with stud walls above. 

 

You can seal each room as a separate envelope and keep air from getting behind the boards and ceiling 

 

As a business I only do about 10% of our site work in wet backing 

It’s only slightly more expensive when you offset the saving in materials

I could do either on my builds but always find wet plaster to be colder 

 

[Iceverge]

Wet plaster.

 

Look up the Denby Dale house on You Tube. Some excellent videos there. 

 

Also double your insulation values. 

[DannyG]

We're also going brick & block and we're planning to use liquid vapour membrane (passive purple airtight paint) on all internal blockwork of external walls as well as the first 1-2 metres of any adjoining internal block walls followed by wet plaster.

 

We'll also brush on passive purple anywhere walls/floors meet and around joists, inside chases, etc.