Single skin 140mm with EWI

[K78]

I’m really struggling to find section details of 140mm block walls with EWI. 

 

This is all my search has uncovered.

 

Can anyone point me in the right direction?

 

Thanks

[PeterW]

What are you actually looking for ..??

 

structural designs..??

 

BBA approved designs ..??

 

Standard details only work where you have a standard build (think developer / NHBC) and are only useful to illustrate a point. 

 

If you are planning to use this design - which would need Insulation both sides from what we have discussed previously - then your architect / Structural Engineer need to sign off on it or produce the calculations needed.

 

Once you have that, and you are using the manufacturers standard installation methods for the insulation, you have everything you need. 

 

 

[K78]

I wanted something to show a builder I’ve been discussing it with. He’s not convinced and says it should be 215mm (block laid flat). He says that BC won’t like 140mm without a approved detail.

 

Ive read similar on another forum which is why I was considering joining the AECB. They have silver standard examples of 140mm externally insulated walls. 

 

 

[Miek]

140mm is the minimum width for a two storey single skin IIRC. But 140 is non standard and costs more so it can be simpler  to use a standard 215 block instead. 

[K78]

1 hour ago, Miek said:

140mm is the minimum width for a two storey single skin IIRC. But 140 is non standard and costs more so it can be simpler  to use a standard 215 block instead. 

 

This is exactly what I’ve been thinking today. No need for internal insulation either which I really want to avoid. 

 

Less problems if I ever sell too. 

[PeterW]

35 minutes ago, K78 said:

 

This is exactly what I’ve been thinking today. No need for internal insulation either which I really want to avoid. 

 

Less problems if I ever sell too. 

 

Why avoid internal ..?? 

 

You'll need to have walls over 400mm thick to do that design. 

[K78]

1 hour ago, PeterW said:

 

Why avoid internal ..?? 

 

You'll need to have walls over 400mm thick to do that design. 

 

‘I’d rather use thicker external insulation. One job rather than two. 

[PeterW]

Cost of fixing system will start to outweigh your thicker insulation costs. Also consider final finish on the insulation and how you will manage windows and doors. 

 

215 on flat will be 50% more expensive on blocks and mortar too. 

[Miek]

I looked into building to passive standard with single skin and EWI thinking it would be cheaper and simpler. But I changed my mind and went for a 300mm full fill cavity instead. EWI to passive thickness was a bit pricey and quite a fiddle to install, also needs more specialist trades when compared to a cavity build which is far more common. I also felt that external block and render was more durable than the thin coat EWI render systems, and far easier to fix things to, like downpipes or overhead cables. 

[K78]

19 hours ago, PeterW said:

Cost of fixing system will start to outweigh your thicker insulation costs. Also consider final finish on the insulation and how you will manage windows and doors. 

 

215 on flat will be 50% more expensive on blocks and mortar too. 

 

The blocks are a higher expense no doubt. I can get 100mm locally for 90p but the cheapest 140mm I can find are £1.60. I’m sure I can find a better price on the 140mm.

 

My windows are big so I’m not too worried about lack of light. I’d have them sat in boxes situated between the wall and insulation. 

 

Doors ive not thought about tbh. 

 

Finish will be timber cladding with insulation between batons. 2 x 50mm (horizontal then vertical) rather than 1x 100mm. 

 

Edited July 17, 2019 by K78

[PeterW]

You can’t do the cladding like that - it needs an air gap and a drained cavity so you can’t fill fill. 

[K78]

7 minutes ago, PeterW said:

You can’t do the cladding like that - it needs an air gap and a drained cavity so you can’t fill fill. 

 

Ive seen quite a few on greenbuilding forum? That is where I got the idea. There is still a air gap between the insulation and cladding. 

 

If it has to be 100mm batons so be it. I just want to keep things as simple and cost effective as possible. 

 

I prefer ewi with cladding rather than render. The render system can look awful after a few years. 

[Russell griffiths]

You don’t need a baton at all you are thinking house when you need to think office block, lots of commercial systems that use aluminium bars fitted to the outside of the insulation with long fixings, I think a lot use a counter bracket fitted through the insulation. 

 

Still not convinced on your 140mm blocks, good luck getting someone to lay them. 

[K78]

2 hours ago, Russell griffiths said:

You don’t need a baton at all you are thinking house when you need to think office block, lots of commercial systems that use aluminium bars fitted to the outside of the insulation with long fixings, I think a lot use a counter bracket fitted through the insulation. 

 

Still not convinced on your 140mm blocks, good luck getting someone to lay them. 

 

‘I’m going 215mm. The saving isn’t worth the hassle.