Cavity closers

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Hi.

Can someone tell me the correct procedure for closing window and door cavities.

I know you can buy cavity closers specifically for this, but the BCO has said that he is happy for us to just close the cavity with the 60mm of insulation that we were using for the wall cavity and use some DPC for the external wall.

Sounds a bit time consuming, so I may just buy the proper product, but is what he is saying OK to do.

Also what is the best way to close the cavity on the bottom of the door opening. One of the tradesmen said that he just fills it with concrete, but I can't see that being correct as you're breaching the cavity.

Is a cavity closer sufficient. I don't know if it is strong enough to support people walking over it.

Thanks.
 
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Hi.

Can someone tell me the correct procedure for closing window and door cavities.

I know you can buy cavity closers specifically for this, but the BCO has said that he is happy for us to just close the cavity with the 60mm of insulation that we were using for the wall cavity and use some DPC for the external wall.

Sounds a bit time consuming, so I may just buy the proper product, but is what he is saying OK to do.

Also what is the best way to close the cavity on the bottom of the door opening. One of the tradesmen said that he just fills it with concrete, but I can't see that being correct as you're breaching the cavity.

Is a cavity closer sufficient. I don't know if it is strong enough to support people walking over it.

Thanks.

The "proper thing" I payed for was just celotex-type insulation board with some DPC glued on and some tags for holding it in place.
You can also get some fancy concertina-types.

But, just fit in a piece of foam board nice and tight and/or fill the gaps with expanding foam. Wedge a piece of DPC between the insulation board and the outer leaf and bend round under the window frame and you basically have what I payed for.

However, if the windows are PVC and extending into the cavity as per regs, there is no point in the DPC at all.

Cavity on door opening. I just filled with concrete (form a trough with some DPM), which does create a thermal bridge. But I thought a heavy traffic area with just a cavity closer would be a bad idea.
You could create a narrow thermal break to be bridged by the floor covering (tiles etc).
The best insulated solution - map out the door openings earlier and build the door openings without a cavity extending the floor right the way across to the outer leaf.
 
Agree with Simon.

We use foam board, foam fixed in place to close reveals.

I also echo what he said about door openings and the floor detail. It is impractical to fit cav clodgers at this junction and using dpm and concrete or screed is the best solution.

In fact, all the things he said remind me of stuff i have said in the past on this very forum...... :idea: :LOL:

Great minds eh. :mrgreen:
 
Thanks Guy's.

The BCO said that he was happy for me to use the cavity insulation with DPC, but I forgot to ask him about the bottom of the doors.

I was a bit doubtful because some of the tradesmen snubbed there noses when I told them what I was doing, thinking that I was penny pinching.

100mm closers seem to be standard and as I have 110mm cavities I thought it would be easier to find an alternative.

Thanks.
 
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There is no need for [expensive] cavity closers. They do nothing that cant be done with insulation cut to fit, or expanding foam.

If you are using aerated blocks, then you can return these round at the reveals

For thresholds, almost every builder builds the wall up in cavity and then everyone scratches their heads.

The inner leaf should be left down one or two courses and the the floor or screed taken across to the outer skin and some insulation foam put between the two for a thermal break. The DPM should be continuous under the threshold too
 
Hi.

I was thinking about the best way around this last night.

At the moment there is a beam and block floor installed and on top of that I need to fit 80mm of insulation and then 70mm of screed.

There is 150mm of block protruding on each of the 4 doors at the moment.

Could I just take these blocks out, fit the 80mm insulation, bridging the cavity and screed over the top of the lot.

I will also add some dpm/dpc around the edges,so that the insulation and screed are protected.

Cheers.
 
Like a lot of things they have their place, when the job is a self build or is being overlooked closely by the client this approach is fine, when the job is bigger or a (not so conscientious) builder is being employed a preformed closer is well worth the extra. They're also attractive to the big house builders as they arrive preformed to save the Bricky even having to measure the opening and speed is f the essence.

Plymouth BC don't actually accept anything but pre-formed closers nowadays partly due to the graphical location but mainly the incapacity of many builders to fit a damcor right or the ability to secure a strip of dpm next to the insulation.
 
Agree with Simon.

We use foam board, foam fixed in place to close reveals.

I also echo what he said about door openings and the floor detail. It is impractical to fit cav clodgers at this junction and using dpm and concrete or screed is the best solution.

In fact, all the things he said remind me of stuff i have said in the past on this very forum...... :idea: :LOL:

Great minds eh. :mrgreen:

Indeed. The trick is to pick up information on one forum and post it on another ;)

Simon.
 
There is no need for [expensive] cavity closers. They do nothing that cant be done with insulation cut to fit, or expanding foam.

If you are using aerated blocks, then you can return these round at the reveals

For thresholds, almost every builder builds the wall up in cavity and then everyone scratches their heads.

The inner leaf should be left down one or two courses and the the floor or screed taken across to the outer skin and some insulation foam put between the two for a thermal break. The DPM should be continuous under the threshold too
Can I ask a question Woody.
Following on from my thread about our windows - I know you say cavity closers are not needed or do samething as foam/other insulation.

But, in one of our windows where 1st fitter had removed old cavity closer and new fitter used timber to butt frame to/ then added dpc, some mineral wool and then foamed.
However I have felt when it's windy or very cold, there's a draught like feeling that wasn't in the old window that had cavity closer- is there a possibility that the original old upvc double glazing was better fitted and no draught due to proper cavity?
 

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