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You were wrong about the 10mm air gap having thermal properties. Fact. Wrong. You were wrong. Thank you and have a nice day :)

Are you nuts or something? You have been arguing whilst talking about a different system. Mine isn't full fill. And I haven't said anything controversial here, just reported what celotex are saying and what is on my plans. I have acknowledged it can be different on site and may be variations.

Why are you being prickly? If you read the first two posts of the thread you would see we solved the problem for ourselves and have corrected course. All my responses since are factual and reasonable. Each to their own, take it or leave it.

Which is what my system is. Dot and dab plaster board, fibolite block, celotex therma class 21, 10mm air gap, outer brick.

Wrong. That would break the outer foil. This is a partial fill system requiring 90mm board and a 10mm air gap. The further from the inner leaf the boards are, the less benefit, hence building inspectors wanting, and celotex recommending, fasteners to hold it against the inner leaf. Also...

Ok so they're being made, and recommended by Celotex, and used by builders for no reason at all? The gap between the boards and inner leaf should be as small as possible, ideally no gap at all (ideally).

I'm relaying what the technical team at Celotex told me. I don't doubt that it is more complicated on site but that's what they who design and make the materials say. They literally told me you don't need an air gap and that they test such conditions, but that it will diminish the U value. I'm...

Agreed, but you need around 8mm to fit the fasteners into the space. Less than 8mm gap and you can't use the fasteners and the insulation boards are supposed to be held up against the inner leaf, notwithstanding that some very small gaps from imperfections between the two won't matter. Without...

Wrong. The 10mm air gap is part of the U Value calculation. You can have no air gap at all with the boards we are using and in some ways it would be easier to build that way - e.g. no fasteners required - but the thermal properties wouldn't be as good. A gap also reduces the odds of water...

No, he says on the video that they intend to have the 10mm gap, and it is relevant because it forms part of the U value calculations, as it does in my case. Some insulation requires a 5mm gap when combined with fibolite. If it is full-fill, then that is fine, you can of course do that. But if...

Looks like the same thing happens in the video! He says at the start of the insulation section that they don't have the 10mm gap but that they'll "get it back". They won't get it back unless the boards are off the inner skin and can be pushed in by that amount. The red fasteners are 8mm thick so...

I have some answers in case it is of use to others... - the insulation company (Celotex) explained that their boards work with zero air gap. So can be sandwiched between the two walls no problem. The air gap will help with the U value but not needed because of moisture ingress. Their tests...

Hi all, The extension project rolls on, and has hit a bump in the road. Around 50% of the fibolite block wall is in place. The builder has today began the process of attaching the 90mm, foil backed insulation boards into the 100mm cavity, and then building up the facing brick. He is using...

LOL! What's weird is I've seen pretty much all the episodes of Tales of the Unexpected even though it was before my time.

Interesting, thanks. Funny you should say that as the old extension on my house, which was built in the early 70s and is on the sunny side of the house, has really terrible pointing. The grains fall out like dust if you rub your finger on them. My builder speculated that they must've built it...

Why does the blocks being wet matter? When you say soaked, do you mean like taken from a puddle soaked, or wet patches on the blocks because they've been stored out in the rain all day soaked?

Hi all, Block wall was built up to 5 course yesterday, fibolite. Last ones went in just before 8pm. It has rained over night although it was dry or at least very light rain in the first few hours after last blocks went in. Looks like heavy rain due all afternoon today though. How long before...

Yes, but don't the crushed feet basically mean holes in the slab which will be points of weakness? Or are the bars amd slab as a whole going to work together to outweigh that?

I blame the building inspector for recommending it. Not that they actually examined the ground in their 25 second visit, which I'm paying hundreds of pounds for. Oh well. Based on what you've seen, would that reinforcement do any harm based on how it ended up being a tad uneven with some...

How long after pouring are you supposed to wait before putting weight on it. My builder has put fibolites on there in seven stacks of ten blocks in a line across the slab on boards. Pour was five days ago.