Foundations??

[Nickfromwales]

4 minutes ago, Iceverge said:

 

Of course you could.

 

The diffusion scaremongers will along shortly to theorise us to death about how structures need to "breath" outwards no doubt . This completely forgets thehuge relative disparity in magnitudes of diffusion driven moisture and moisture carried by air leaks.  It's often hundreds of times more. 

 

It's like worrying about a drip in the ceiling of your pleasure yacht when there's a hole in the hull as big as a my boot. 

 

An immaculate Airtightness layer can go anywhere in the wall and it'll work fine….

Yes, I do like the logic, it’s just trying to get stubborn architects and designers to lift the needle off their heavily scratched records will be the hard part, as if they don’t agree then you’re back to doing it “the good old way”. 
 

I’m currently specifying M&E / renewables / airtightness options etc for a SIPs build client(s) and wish to use the Aero Barrier system for airtightness; the timing is fortuitous to do so right at this moment in the construction phase and would save a lot of labour / membranes / tapes and some possible minimal deconstruction of already installed stud work > external walls & roof if we can.

 

The more I look at the Aero Barrier system, the more I’m liking it tbh.

 

https://www.aerobarrieruk.co.uk For anyone curious. Some good vids on YouTube too. 👍

 

My difficulty (job for Monday) is to approach the ‘higher powers’ and beg for their almighty permissions, via argumentative logic, for us to do away with the VCL that they’ve specified to be installed on the interior face of the SIPs panels (wall to roof continuous) in light of (near) zero interstitial air or moisture flow in the fabric of the structure; demonstrable by the AT result from Aero Barrier test certification.

 

Anything wrong with that idea folks?  

[lizzieuk1]

16 minutes ago, Nickfromwales said:

guess this is a warning to remain vigilant at the time it matters most, as some may just steam through the construction and not realise how impactful even a 10mm undulation will be downstream

For a stonemason the tolerance is 3mm so, I'm sure hubby will be all over that, it may take longer but he won't let it slide! 

[JohnMo]

2 minutes ago, lizzieuk1 said:

tolerance is 3mm

I come from an engineer background at one point in my career I was working to 0.0005" or 0.0127mm. Walls were done to less than millimetre where this was possible.

 

 

[lizzieuk1]

On 01/03/2025 at 11:42, JohnMo said:

I come from an engineer background at one point in my career I was working to 0.0005" or 0.0127mm. Walls were done to less than millimetre where this was possible.

 

 

Well done JohnMo, looks like you've set the bar high!

[lizzieuk1]

14 minutes ago, Nickfromwales said:

The more I look at the Aero Barrier system, the more I’m liking it tbh.

Looks like a clever system Nick, any ideas on cost?

[lizzieuk1]

34 minutes ago, Nickfromwales said:

The beauty of coming on Buildhub at this stage is to get yourself in check, so happy days. Forewarned is forearmed, and so on   

It sure is!

Thankyou buildhubbers, you are all a vast knowledge base and I really appreciate your time with my  questions!

[JohnMo]

6 minutes ago, lizzieuk1 said:

Looks like a clever system Nick, any ideas on cost?

I wouldn't go that route with Durisol without first sealing every block.

[Nickfromwales]

2 hours ago, lizzieuk1 said:

Looks like a clever system Nick, any ideas on cost?

For a medium sized 3 bed SIPs build they’ve said (ballpark) ~£1500, possibly less, and done in a day!

 

They said they’d deal with sealing up the pre-installed ducts in the slab / foul and waste pipe work etc in that price, but I forgot to ask if they masked up the doors and windows.
 

Worst case there is that you’d have to do that ahead of their attendance, but I’d probably opt to do that myself anyways for peace of mind, say with 4mm hardboard or Antinox (same / other) sheeting, (Link here to random grab) , however, they also said that foam around doors and windows, dressed in properly, would suffice!  

 

If so, that would negate all the taping around openings and associated costs, making their price seem unbelievably good value for money.
 

That said, (as I am employed by clients and have to mitigate against failures for 6+ years), I asked if it was better for longevity if the windows and doors etc were AT taped (belt & braces) and the obvs answer was “yes”, but again that’s DIY’able with relative ease. Openable doors and windows are dynamic so there’s going to be movement when slammed shut etc, so my 2 cents is to foam and tape, but the chap says AB is fine to use with just the foam in situ. I think it would be a good day out for me to go see a live install. God I’m boring, I used to be cool. 🥲.

 

AB only do positive pressure testing on the day, not positive > negative x10, but if the air can’t get out then one can only surmise that it cannot get in either? Not sure if that test satisfies BCO, but as you’ll need to do an as-built AT test at the end of the build anyways I guess the matter is moot. I’d wager there are plenty of OCD freaks out there who would do an independent push / pull AT test after AB have left, to check / validate, but I have to admit I’d probably be one of those freaks. I can’t recall if BCOs ask for anything prior to the as-built test as we’ve always done both. Anyone?

 

From what I gathered on the phone to a very helpful chap at AB yesterday, they quote provisionally on a m2 basis, so easy enough for you to get a ballpark number off them for the cost of a phone call / email. @lizzieuk1, the price I had was for SIPs so may be a bit higher for you with woodcrete as I assume it would consume a lot more product? I honestly don’t know, but I will be finding out when I speak to their technical team again for my current and other upcoming build projects. 👌. 

 

I had seen the Isotex project get obliterated internally with Passive Purple, and not great results over the woodcrete tbh, not a fault of the product btw just a lot of ‘pores’ to the surface of woodcrete. I also think the installers (marched on by said Neanderthal) could have been more sympathetic, but I think he was limited by IQ. Final result was north of 3ach……😳. 

 

I can’t help wondering if the AB system would have been quicker & better there, I very much expect so, but I can tell you hands down it would have been massively, like HUGELY cheaper. The total spend on the woodcrete to get to the point where it was 50% parged (over 100% of the reachable interior surface area) and 100% purple’d was well into 5 figures. They even sprayed the inside of the SIPs roof!
 

For completeness, this was around Covid, and I don’t think there was much noise about AB at that time. It was mentioned here a good while back, but it’s Saturday and I can’t be arsed to look for it. First member to find it wins a prize*. 

 

(Please nobody who’s DIY’d respond to those numbers, this was a commercial project where people were charging a premium to operate their companies at the request of the clients who were almost entirely ‘hands off’).

 

Also with noting that Adam White at Intelligent Membranes is a super helpful chap, and he was happy to come to site and meet up with me to discuss the best possible solution (for the Velox project) and between his input, the strategic use of Passive Purple and my OCD / methodology we got that in at 0.88 provisionally and then to 0.66 with some trouble shooting. I think it could (would) have been easy enough to get it much better, sub 0.6, but that’s as close to PH as they needed to be as they didn’t (iirc) go for the arse-ache of full certification. 
 

@lizzieuk1 I would recommend you explore this with AB, but either way I would also recommend that you do install other airtight measures at sole plate level > openings > wall plates > roof junctions accordingly, eg the bits / areas people forget about until it’s too late to do anything about it.  We can tell you where / how / with what as you progress. 
 

You’ll also need to parge the window and door reveals with woodcrete, so the AT tape has something uniform to stick to, also, as AT tape onto a porous / perforated surface will do nothing. On the Velox one where I was instructing the builder on the clients behalf, we put the paint on version of Passive Purple where the tapes landed, which gave excellent adhesion, and that was still getting applied over the parge coat. (The PP can be sprayed or applied by brush / roller, there are 2 different viscosity versions of that product available, to allow either method of application). 

 

Maybe the AB route would be quickest and simplest way forward for anyone considering woodcrete, but also (to be fair) this may be better vs tape and membrane regardless. Only place it’s not going to be an option is for cellulose blown frames where the membranes required to hold in the insulation.

 

Last point, I promise, is about timing of when you want to get AB done. I’ve spent a bit of time this week looking into this. It’s less than ideal (but not impossible) to have AB come into an existing residence and make it airtight retrospectively. But just think about the scene from Mr Bean when he masks off everything to paint his house (including each individual grape 🤣 and that’s how far you’d have to go to not have this product nicely layered over everything you own. So get AB in at the point of becoming weathertight, doors and windows in, roof on, no internal finishes on floors or walks etc, and that’s about the sweet spot methinks. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

* I lied about the prize. 

[Nickfromwales]

On 01/03/2025 at 11:52, JohnMo said:

I wouldn't go that route with Durisol without first sealing every block.

I’d say get a quote first, then compare. May just turn out to be quicker, cheaper and better overall. 

Edited March 2 by Nickfromwales
Cheaper not chewier lol.

[JohnMo]

1 minute ago, Nickfromwales said:

I’d say get a quote first, then compare. May just turn out to be quicker, chewier and better overall. 

Not saying don't go that route, just the amount of holes in the blocks, may make the process less cost effective and difficult. Seal the blocks first, then fill boots. 

 

[Nickfromwales]

18 minutes ago, JohnMo said:

Not saying don't go that route, just the amount of holes in the blocks, may make the process less cost effective and difficult. Seal the blocks first, then fill boots. 

 

Elementary my dear Watson.

 

If what I’ve read makes sense, then the airborne atomised product will work its way into the little nooks and crannies, vs try and form a layer on the surface of the block. I think this would consume a bit more product obvs, but looking at previous projects and time / labour / grief, I think this may be the way forward, just to take the plunge and allow the AB system to do its thing.

 

They demonstrate this system closing a hole the size of an A4 sheet down to the size of a postage stamp. 

 

I’ll speak to them and see what they have to say, but I doubt the product is that expensive for them to quibble project to project, material to material, perhaps.

 

I’ll let my fingers do the walking 👍

[lizzieuk1]

21 hours ago, Nickfromwales said:

Elementary my dear Watson.

 

If what I’ve read makes sense, then the airborne atomised product will work its way into the little nooks and crannies, vs try and form a layer on the surface of the block. I think this would consume a bit more product obvs, but looking at previous projects and time / labour / grief, I think this may be the way forward, just to take the plunge and allow the AB system to do its thing.

 

They demonstrate this system closing a hole the size of an A4 sheet down to the size of a postage stamp. 

 

I’ll speak to them and see what they have to say, but I doubt the product is that expensive for them to quibble project to project, material to material, perhaps.

 

I’ll let my fingers do the walking 👍

Wowser, thanks Nick for such a thorough run through of all that! 

As you say it is worth asking the question re cost and a conversation around woodcrete to see if that approach is a cost effective/practical option or if parging first would be better. (Obv they will want to sell as much product as they can so I guess critically appraising their answer is in order) 

 

The one issue I could see for us, is that we have been looking at a posi joist roof structure & blown cellulose which, sounds like it may not be suitable for that system. The cutting & fitting of pir between rafters (and now a need to tape all sides) is so painful, not to mention the cost, so we're looking for a better way! 

[lizzieuk1]

58 minutes ago, Nickfromwales said:

We can tell you where / how / with what as you progress.

😊 thanks

[Iceverge]

Aerobarrier is a buildhub thing. 

 

 

Typically seems to be used by people to go from "Very good"---> "Excellent" . Anyone who's not aiming for "very good" already is too stupid to understand and should go back to sniffing solvents. 

 

I don't think it's going to cure an absolute leaky bucket of a house but it's certainly the icing on the cake. 

 

It can be redone in an old house but requires Statzi levels of masking to avoid contaminating Aunt Janes prize doilys. 

 

I think it really shines where you've screwed up some element of the design process and want to get the number down. 

 

Properly planned and executed airtightness isn't that hard for the non glue sniffers out there. 

 

 

 

 

 

 

 

 

 

[Iceverge]

4 minutes ago, lizzieuk1 said:

The cutting & fitting of pir between rafters (and now a need to tape all sides) is so painful, not to mention the cost, so we're looking for a better way! 

 

DO NOT DO THIS!!!!!!!

 

JJI joist ( or cut lumber) roof and blown cellulose is the biz. 

[JohnMo]

3 minutes ago, lizzieuk1 said:

posi joist roof structure

If you going that direction, you will need a vapour and airtight membrane inside. Then the wall airtight layer makes sense internally, not external. Then bond the ceiling/roof membrane to the block work inside. 

[Iceverge]

The more I read the more I think woodcrete is irredeemablly compromised. 

 

If you want solid feeling walls go for masonry and full fill cavities.

 

If you want speed go for factory TF. 

 

If you want DIY go for stick build and cellulose. Line with Osb behind the plasterboard for ultimate solidity. Add a masonry skin for 500 year durability. 

 

 

 

 

 

 

 

 

[lizzieuk1]

13 minutes ago, Iceverge said:

 

DO NOT DO THIS!!!!!!!

 

JJI joist ( or cut lumber) roof and blown cellulose is the biz. 

In preference to posi joists? 

Then underlined with insulation for cold bridging?

[lizzieuk1]

8 minutes ago, Iceverge said:

The more I read the more I think woodcrete is irredeemablly compromised. 

It is used quite widely in other countries though so, there must be positives that drive the usage.

[JohnMo]

11 minutes ago, lizzieuk1 said:

It is used quite widely in other countries though so, there must be positives that drive the usage.

Following a hurricane - one house left, the Durisol house being constructed.

 

Doesn't rot

Doesn't burn

Doesn't seem to blow down (once concrete filled. 

 

[G and J]

39 minutes ago, JohnMo said:

Following a hurricane - one house left, the Durisol house being constructed.

 

Doesn't rot

Doesn't burn

Doesn't seem to blow down (once concrete filled. 

 

Leaving one very hungry wolf presumably?

[Iceverge]

3 hours ago, lizzieuk1 said:

In preference to posi joists? 

Then underlined with insulation for cold bridging?

 

Yup, they create closed "boxes" which is easier to get a good densepack of the cellulose. 

 

There's the square root of zero thermal bridging through the OSB webs of an I joist. I would counter batten underneath for a service cavity though. 

 

 

Something like. 

 

Tiles

Tile battens

Counter battens

Breather membrane

11mm OSB

350 mm I joists with Cellulose.

Membrane 

20*70mm battened service cavity

Plasterboard 

Skim.

 

U value about 0.11. 

 

Alternatively 

 

Tiles

Tile battens

Counter battens

Breather membrane

11mm OSB

220mm sawn joists with Cellulose.

Membrane 

95*45 mm battened service cavity with mineral wool or cellulose 

Plasterboard 

Skim.

 

U value about 0.14 but all off the shelf material from your local merchant and lots cheaper to boot. 

 

 

 

[lizzieuk1]

3 minutes ago, Iceverge said:

 

Yup, they create closed "boxes" which is easier to get a good densepack of the cellulose. 

 

There's the square root of zero thermal bridging through the OSB webs of an I joist. I would counter batten underneath for a service cavity though. 

 

 

Something like. 

 

Tiles

Tile battens

Counter battens

Breather membrane

11mm OSB

350 mm I joists with Cellulose.

Membrane 

20*70mm battened service cavity

Plasterboard 

Skim.

 

U value about 0.11. 

 

Alternatively 

 

Tiles

Tile battens

Counter battens

Breather membrane

11mm OSB

220mm sawn joists with Cellulose.

Membrane 

95*45 mm battened service cavity with mineral wool or cellulose 

Plasterboard 

Skim.

 

U value about 0.14 but all off the shelf material from your local merchant and lots cheaper to boot. 

 

 

 

Amazing, thankyou 😊

[Iceverge]

20 hours ago, JohnMo said:

Following a hurricane - one house left, the Durisol house being constructed.

 

Doesn't rot

Doesn't burn

Doesn't seem to blow down (once concrete filled. 

 

 

Fire protection is deffo an advantage. 

 

It's the airtightness that I'm disappointed by. 

 

Also they don't appear to be inherently sealed against water ingress either, necessitating extra rain screens. The apparent difficulty chasing services (watch this space) also has left me scratching my head a little. 

 

TF would be just as easy to DIY and as you need a rain screen and service cavity anyway I think I'd be going that route.

 

Having heard tales on here of folk getting shafted and losing deposits to dodgy manufacturers of ICF and offsite timber frame I'd be cautious of that too.

 

Stick build or masonry tends to be less financially risky in my opinion. 

 

 

[Nickfromwales]

16 hours ago, Iceverge said:

Having heard tales on here of folk getting shafted and losing deposits to dodgy manufacturers of ICF and offsite timber frame I'd be cautious of that too.

That ICF goon shouldn't make us paint the rest of them with the same shitty brush. Also not the ICF manufacturer at blame there (afaik?), just that goon of a supplier in the UK.

 

Did I mention the word goon?