Airtight Conversion

[walsall]

Afternoon,

Don’t normally do domestics, but am involved with a smarthome project. The inside leaf is blockwork and will be dry lined. Normally I’d just chase the cables and boxes in the wall.

The builder wants to apply a parge coat to the wall to increase airtightness as a base to the dot/dab boards. One solution is to clip the conduit to the walls on top of the parge coat, just chasing out the boxes and use lots of adhesive behind to make them airtight. Then just have bigger dots to clear the cables/oval conduit.
Has anyone with experience of these obsessive airtight issues got any better ideas?

I can’t tell you how much I prefer unistrut & galv trunking!

 

[DPG]

I'm intrigued by this. Is a normal two-leave cavity wall with plasterboard on it not airtight enough? Daz

 

[walsall]

I'm intrigued by this. Is a normal two-leave cavity wall with plasterboard on it not airtight enough? Daz

Not that airtight at all. The plasterboard isn't too bad but dot/dab edges, joins etc allow quite a lot of air movement through the cavity. MVHR systems need the house to be very airtight to get the best out of them.

 

[Marvo]

I don't have any advice for you I'm afraid but I do have a couple of questions. Firstly are you going to seal the cable or conduit entries into the backboxes? Secondly can I ask exactly what is 'dot and dab'? It's a phrase I've seen used a few times but never figured out what it is.

 

[trev]

I don't have any advice for you I'm afraid but I do have a couple of questions. Firstly are you going to seal the cable or conduit entries into the backboxes? Secondly can I ask exactly what is 'dot and dab'? It's a phrase I've seen used a few times but never figured out what it is.

It's where the plasterboards are fixed with an adhesive

 

[Marvo]

Thanks Trev. Are the plasterboards being fixed to the existing brick wall? If so why? Wouldn't it be easier to just plaster the wall?

 

[trev]

Thanks Trev. Are the plasterboards being fixed to the existing brick wall? If so why? Wouldn't it be easier to just plaster the wall?

Yes they're fixed direct to brick/block work but I've got no idea if it would be easier to plaster direct.
I'm a sparky

 

[ayjay]

no need to use oval conduit for the drops imo, we never have
just surface clip to the blockwork

 

[peterinreading]

We used the following sequence recently for a similar job where the sealing was for damp proofing rather than air tightness:

1. Chase the wall for the cables and boxes
2. Seal the wall
3. Fix the cables and boxes using sealant for every hole you drill to maintain air/water tigntness
4. Fix the plasterboard

 

[davesparks]

Thanks Trev. Are the plasterboards being fixed to the existing brick wall? If so why? Wouldn't it be easier to just plaster the wall?

Yeah, lumps of wet adhesive are launched at the wall then the plasterboards are pressed onto it.
The advantage is that it only needs a skim afterwards which will be dry in no time in this modern world of everything having to be finished yesterday if not sooner.

 

[Engineer54]

I always thought these wooden framed buildings needed a heavy duty PVC (or whatever) vapour lock membrane. That's what they used to use anyway. To be honest i wouldn't even give a Thank You for these modern matchstick wood framed houses. They are never going to come even remotely close to lasting as long as a brick or brick and block construction.

At least when they built wood framed houses/buildings 300/400 years ago they used OAK!! Try screwing a screw, or knocking a nail into those old oak timbers, ...no chance, those matured oak timbers are now as hard as steel!! lol!!

Another thing, i wouldn't be wiring the lights looping through the switches, you'll not be getting all the connections into some of those 25mm back boxes!! lol!!

 

[shanky887614]

Yeah, lumps of wet adhesive are launched at the wall then the plasterboards are pressed onto it.
The advantage is that it only needs a skim afterwards which will be dry in no time in this modern world of everything having to be finished yesterday if not sooner.

its much quicker and cheaper than the old method, buy chamfered boards, tape it then a tiny bit of filer/plaster over joins and quick sand and its ready to paint

 

[davesparks]

Exactly quicker and cheaper therefore by modern standards it must be better!

 

[walsall]

We used the following sequence recently for a similar job where the sealing was for damp proofing rather than air tightness:

1. Chase the wall for the cables and boxes
2. Seal the wall
3. Fix the cables and boxes using sealant for every hole you drill to maintain air/water tigntness
4. Fix the plasterboard

Thanks Peter -I guess that's the route we'll have to follow...
This I going be something we see much more of as the building regs get tightened up.

 

[R G]

Don't know about airtight conversion but just lately all my customers are completely watertight thats for sure...