Cavity width in standard cavity wall.

Slig · 10-09-2008 01:04PM #1

TJGer wrote: »

About to insulate the cavitys in a new house. The company doing it do both wool and bead. Just curious as to which one would be better. The cavity is 180mm in a concrete block house. Any advice is welcome!

180mm cavity?

TJGer · 10-09-2008 05:17PM

Slig wrote: »

180mm cavity?

Yeah 180mm. Extra space for insulation apparently. Advice from the builder (father in law!).

sydthebeat · 10-09-2008 07:51PM

TJGer wrote: »

Yeah 180mm. Extra space for insulation apparently. Advice from the builder (father in law!).

have you anyone certifying the build??

what centres have you wall ties at?

TJGer · 10-09-2008 10:34PM

sydthebeat wrote: »

have you anyone certifying the build??

what centres have you wall ties at?

Our engineer is certifing and the builder is registered with Homebond
Not sure on the wall ties, why?
Went with the wool after all. Seems to have filled the cavity well.

sydthebeat · 11-09-2008 08:30AM

TJGer wrote: »

Our engineer is certifing and the builder is registered with Homebond
Not sure on the wall ties, why?
Went with the wool after all. Seems to have filled the cavity well.

interesting, i was lead to believe that HOMEBOND wont stand over any cavity larger than 150mm.... can you clarify this for me.

wider cavities require specialist design. The wall tie centres need to be increased to provide stability to the structure. In some cases specialist wall toies need to be used. If your engineer has signed off this stag ethen he/she is taking the responsibility that the build conforms with the building regs, including part A, structure. the wall tie type and number need to comply with I.S. 325 : Part 2 - Irish Standard Code of Practice for Use of Masonry

muffler · 11-09-2008 08:40AM

sydthebeat wrote: »

interesting, i was lead to believe that HOMEBOND wont stand over any cavity larger than 150mm.... can you clarify this for me.

wider cavities require specialist design. The wall tie centres need to be increased to provide stability to the structure. In some cases specialist wall toies need to be used. If your engineer has signed off this stag ethen he/she is taking the responsibility that the build conforms with the building regs, including part A, structure. the wall tie type and number need to comply with I.S. 325 : Part 2 - Irish Standard Code of Practice for Use of Masonry

Its more than interesting in that I dont see why an engineer would be needed (other than stage payment and cert. compliance) at all for any structural inspections. Its the Homebond inspector who would be responsible for structural elements.

TJGer, have you documentation to say that your house is registered with Homebond or is it simply a case that your builder is affiliated only?

Slig · 11-09-2008 09:26AM

This is straying a bit off topic (my fault for bringing it up, sorry) and no doubt worrying the OP but can we give an answer.

From my experience, and I'll have to look it up but any wall construction cavity larger than 110(ish) needs more wall ties for a start. The DOE have only certified systems to use a 150mm cavity. Any system with a larger cavity requires an independant structural engineer to carry out a survey and submit it to the DOE for approval.
Thats what I got from the various reps (couldnt get a straight answer from the DOE) but I'll do a bit more digging.

muffler · 11-09-2008 09:42AM

Slig wrote: »

This is straying a bit off topic (my fault for bringing it up, sorry) and no doubt worrying the OP but can we give an answer.

You are quite right Slig. Its hard not to run off topic(ish) at times but what I'll do is open a new thread to debate cavity widths.

muffler · 11-09-2008 09:44AM

For anyone wishing to debate wide cavities i have opened this thread and transferred a few posts from another thread.

Edit: This post obviously should be at the top but as the others are older they will appear first.

Slig · 11-09-2008 09:48AM

muffler wrote: »

For anyone wishing to debate wide cavities i have opened this thread and transferred a few posts from another thread.

thanks, but you missed the one at the end:D

muffler · 11-09-2008 09:49AM

Slig wrote: »

thanks, but you missed the one at the end:D

Oops

mossysheehan · 30-01-2009 08:46PM

I know this thread hasn't been used in a while but this is something i've always been fairly interested in. What is the best wall construction when using concrete blocks? My father is at planning stages at the moment and i'm trying to decide on the wall construction, as efficient and easily constructable as possible. Think i've rounded it down to two:

1. 150mm cavity with 100mm Kingspan k8 or similiar insulation(how thick can you get this stuff, it only goes to 65mm on the brochure i saw) Wet plaster finish and outside rendered.

2. Avoiding thermal looping and poorly placed insulation, uninsulated 50mm cavity, with skimmed, insulated plasterboard with servive gap and insulation between battens. I know there is issues with heat loss at the jambs, cills and head of window and door opes here.

Any suggestions or advice on these?
Or other suggestions on energy efficient and airtight cavity wall construction?

Also, does skim on plasterboard provide as good airtightness as in a sand/cement finish?

Looking forward to hearing any input,
Moss

Bubbling · 17-07-2014 04:36PM

mossysheehan wrote: »

I know this thread hasn't been used in a while but this is something i've always been fairly interested in. What is the best wall construction when using concrete blocks? My father is at planning stages at the moment and i'm trying to decide on the wall construction, as efficient and easily constructable as possible. Think i've rounded it down to two:

1. 150mm cavity with 100mm Kingspan k8 or similiar insulation(how thick can you get this stuff, it only goes to 65mm on the brochure i saw) Wet plaster finish and outside rendered.

2. Avoiding thermal looping and poorly placed insulation, uninsulated 50mm cavity, with skimmed, insulated plasterboard with servive gap and insulation between battens. I know there is issues with heat loss at the jambs, cills and head of window and door opes here.

Any suggestions or advice on these?
Or other suggestions on energy efficient and airtight cavity wall construction?

Also, does skim on plasterboard provide as good airtightness as in a sand/cement finish?

Looking forward to hearing any input,
Moss

Hi Moss,

What did you specify / build in the end.

Kingspan have today quoted me a u value of 0.17 W/m2K for a 100mm block work inner leaf, 100mm Kooltherm K8 Cavity board, 40mm Cavity (140mm total cavity) and 100mm blockwork outer leaf, plastered internally and externally. This is well within the Part L threshold of 0.21 W/m2K and is within the 150mm max cavity width that is structurally advised. This seems to tick all the boxes as far as I can see?

Or am I missing something?

As this is such a straight forward construction, why then is a dry lining board often specified in addition to having cavity wall insulation in similar construction?

Thanks!

BryanF · 17-07-2014 05:08PM

start your own thread this one is 5 years old!!! ( and applicable to different much older regulations )

Cavity width in standard cavity wall.

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