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Bad Airtightness Test Result


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2 minutes ago, AliG said:

 

Every house I have had previously they only laid the kitchen floor up to the feet of the kitchen units, I thought I was being smart asking for the whole floor to be done.

Yeah I know what you mean. I’ve had a few places that only had tiles on the ‘open’ floor space. But what the hell are the builders thinking by leaving some of the tiles they have put down ungrouted.

 

It really goes to show that you need to be on site everyday keeping an eye on what the hell they are doing! I can’t remember how many times I had to get the builders to redo something that they had tried to shortcut. God knows how much I missed!! 
 

This is why so many on here do everything themselves.... it may take years longer to get finished, but at least it’s done right. 

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10 minutes ago, Gav_P said:

 

This is why so many on here do everything themselves.... it may take years longer to get finished, but at least it’s done right. 

This is why I didn't bother asking them to come back and do these jobs. They are quite small and they just wouldn't do them carefully enough. I don't think they understand air tightness really.

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11 hours ago, AliG said:

I don't think they understand air tightness really.

My neighbour had new windows fitted so popped around to see what everything looked like  and got hatting to the fitter.  He claimed that if you made a house airtight then it would be stuffy.

I said the MVHR deals with that.  He did not have a clue what I was talking about.  He kept claiming that you need some 'holes' to 'stop the place overheating'.

Neighbour still gets leaks, but they are nothing to do with the windows.

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Working my way slowly through the fixes.

 

A problem area consistently has been the WC and hall cupboard which stick out from the house so have a flat roof above them.  The roof is a warm flat roof made from a concrete plank with PIR on top of it. It was the very last piece of the house completed as we were waiting for the stone archway at the front door that is part of it.

 

This area has always been colder than everywhere else in the house, the heating needs to run much much more. I had the builders remove the WC ceiling and check for holes above causing draughts, when they did this I could see a gap between the wall and the concrete plank where I could see the insulation  in the cavity and asked them to fill this but there is still an issue.

 

It occurred to me that there is a MVHR vent in the cupboard ceiling and if I removed this I could see a little of what is going on between the plasterboard and the concrete plank. I removed this and stuck my phone up there.

 

I could only see the plank to wall junction on the inside and there was a gap there also. I suspect there might be a gap at the third edge that I have not seen. Also the builders consistently fill gaps by just pushing rock wool into them which simply is not air tight enough, there seemed to be rock wool in various places so I could not see what was behind it. Also there is virtually no wind at the moment so I cannot feel any particular draughts, just general cold and air movement.

 

I am thinking that I bite the bullet and cut a couple of holes near the edges of the ceiling so I can both see if there are gaps and then fill them in. I don’t want to cut holes in the ceiling but this area has been an issue for some time.

 

Simple question. What’s going to be easier to patch. A straight edged hole cut with a multi tool or a 100mm circular hole cut with a hole saw? I was thinking a circular hole is less likely to see the plasterboard breaking up and cracking at the corners. Or am I overthinking it and it doesn’t matter?

 

 

 

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3 minutes ago, AliG said:

100mm circular hole cut with a hole saw? I was thinking a circular hole is less likely to see the plasterboard breaking up and cracking at the corners. Or am I overthinking it and it doesn’t matter?

@Onoff did a great example of this in one of his posts. Circular hole looked like a nice easy way to go.

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1 minute ago, Gav_P said:

@Onoff did a great example of this in one of his posts. Circular hole looked like a nice easy way to go.

Oh also, I had a moment not unlike yours where I was really annoyed by something the builders had done at a previous house so I just started opening up holes with a hammer... this is not the best option, it was a bugger to fix later. 

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Just now, AliG said:

Thanks. Looks like I should maybe try a 152mm saw as that’s the size of the duct hole that I was able to get my arm right up inside.

Yeah sounds sensible. You can then just put back the extracted round bit with a bit of ct1 or something, and then fine fill. 

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Thanks guys. Looks like I can get a 200mm one pretty cheap. No point spending a lot to cut three or four holes. May as well go as big as possible once I’m making a hole anyway.

 

I would hope it fills nicely but it is in a cupboard so not quite so concerning. If it works well in the cupboard I might try in the WC also. 

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11 hours ago, Onoff said:

Super Rod Cavity Master is an option. Basically a modified Starrett that cuts a shoulder. I've only ever used the steel drop in plates in t&g flooring. You can also use the mesh infills you plaster over. 

Very clever, but I'm going to try the Ebay £6.99 option I think

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OK, got my hole saw. Scary thing to use as the blade keeps turning after you stop the drill and even more scary using it just above your head. I stopped with the hole 90% cut and finished off with a knife.

 

Found the issue. I also ordered an inspection camera for £30 off Amazon and that is helping.

 

The MVHR has to come round a sharp corner and through the Porotherm wall to get from the hall to the WC, it runs above head height in the space between the ground and first floor windows.. They took out the two corner Porotherm blocks and assumed that the PIR behind them was enough to stop draughts. But of course it is not tight in any way.

 

Trouble is, it is such a massive hole, I am not sure how to fill it.

 

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I have know there was an issue here for some time. Other places where the MVHR is taken through the Porotherm it was sealed. Here, however, I think the builders thought it was an inside wall so left it, but it connects to the outside cavity.

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On 05/01/2021 at 22:15, PeterW said:

Biggest hole saw you can find and cut two or three holes with it. Then just glue a bit of batten on the back, smear of filler round the edges when you put it back and job done. 

 

What's done on my house to warmcell (airtight layer is outside) is 100mm hole saw through plasterboard (before plastering), then cut 200x50mm strips of 6mm or so plywood and push that through the hole so it overlaps.  Then drywall screw that plywood so it spans the hole along with one or two screws to hold the original plasterboard disc in place, et voila!  Scrim tape over when it comes to plastering.  I did hundreds of them...

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