Traditional block and stone build

[DaveH]

Hi, first time self builder here. Whilst everyone seems to be going timber frame, ICF, Passivhaus etc my build is a far more traditional block and natural stone construction. This has been a big learning curve and both my architect and builder definitely favour the traditional way of doing things. The shell is constructed and I will be moving towards first fix soon but I definitely have a few questions for the experts here along the way!

[joe90]

Welcome and bring the questions on, we love it. Mine is a traditional block and brick construction but with more than usual insulation and great attention to airtightness detail. Not a passive hous but following its principles. Simply because I want a comfy house that does not cost me a fortune to run in my retirement.

[DaveH]

Thanks Joe90. Lovely part of the world you're in!

 

Unfortunately I have been working abroad a lot this year and I fear that in my absence the cavity insulation (50mm PIR) may not be quite as complete and taped up as I would have liked had I been supervising. There are certainly a couple of other things I'm now wondering the best way forward on:

 

1: the internal blockwork leaf was not pointed so I have some gaps in the mortar which is not good for airtightness I considered wet plastering but I'm now wondering about battening the walls with extra insulation, taping everything up and screwing plasterboard over the top.

 

2: the roof is a very traditional slate roof on 6x2 timber rafters and steel purlins. It has been built as a cold roof so now I'm trying to figure out the best way of achieving a good level of insulation. The 1st floor is built partially into the eaves with the rest being loft/crawl space.

 

Any advice is welcomed.

[Gav_P]

My place is built very similarly to yours... except the main house was done over the last couple of hundred years and I’ve tried to improve the air tightness and insulation whilst reconfiguring and adding a new extension.

 

 I’m interested in the advice that comes forward on this... ?

 

p.s welcome to the forum... it’s been indispensable for me!!  

Edited November 22, 2018 by Gav_P

[Declan52]

Is 50mm pir  in a cavity enough to satisfy building regs?? 

You can parge coat the block work to seal it up then do as you propose.  50mm battens with 50mm insulation in between. Then it's up to you.  You could overboard with more insulation and tape it up then plasterboard. Or use a membrane.  Your going to have to think about cables for plugs switches etc.  Do you put in a service cavity too run all the cables. 

For your roof is it a bungalow with a room in the roof type setup??

If so you can either cut pir to fit between the rafters (not a nice or easy job) then put more pir underneath. 

Or high density rockwool in between and pir  underneath. 

Or cross batten the  roof to give you  200mm and get the  insulation blown in. 

All have their pros and cons. 

[nod]

1 hour ago, DaveH said:

Thanks Joe90. Lovely part of the world you're in!

 

Unfortunately I have been working abroad a lot this year and I fear that in my absence the cavity insulation (50mm PIR) may not be quite as complete and taped up as I would have liked had I been supervising. There are certainly a couple of other things I'm now wondering the best way forward on:

 

1: the internal blockwork leaf was not pointed so I have some gaps in the mortar which is not good for airtightness I considered wet plastering but I'm now wondering about battening the walls with extra insulation, taping everything up and screwing plasterboard over the top.

 

2: the roof is a very traditional slate roof on 6x2 timber rafters and steel purlins. It has been built as a cold roof so now I'm trying to figure out the best way of achieving a good level of insulation. The 1st floor is built partially into the eaves with the rest being loft/crawl space.

 

Any advice is welcomed.

You could wet plaster 

But depending on how much room you are able to looser You could fit and dab with insulated boards 25 mil insulation board would take up 70 mil on each wall 

Or 50 would take 100 off each wall 

[DaveH]

Thanks Declan. Building Regs are perfectly happy with 50mm PIR but with hindsight it just doesn't seem enough to me. The property is actually over three floors on a sloping site but in a chalet style. The top floor has one metre of wall before the roof structure.

 

Nod, the other option I considered was dot and dab insulated boards, paying particular attention to sealing up around the bottom edge (continuous run of adhesive at the bottom and around door casings, switch and socket boxes etc?) I'll price up the cost of materials and the installation time of both options. I do like the idea of being able to run services along battens though without having to chase walls etc..

[PeterW]

Where in the UK are you @DaveH as I can’t see how 50mm hits BRegs unless it’s a conversion or extension ..??

[DaveH]

8 minutes ago, PeterW said:

Where in the UK are you @DaveH as I can’t see how 50mm hits BRegs unless it’s a conversion or extension ..??

 

West Yorkshire

[PeterW]

So that’s a wall U-Value of 0.24.  What’s the DER/TER from the SAP calcs..??

 

I would be looking to add a minimum of 25mm if not 50mm of insulation to all the internal walls after a parge coat or at least pointing up all the gaps. 

 

 

[DaveH]

Parge coat and internal insulation does seem the way to go. Are there any particular pros and cons between dot and dab insulated plasterboard and battens with slab insulation in between? More PIR or EPS or rockwool?

[j_s]

Battens would give more control to make sure everything is sealed behind before the plasterboard goes on and gives you the service void you want as well as less risk (not 0) to insulation when it comes to picture hooks and other fixings to the plasterboard.

You could even do the insulating your self then and make sure it's all done correctly