First timers attempting an ICF and Oak Frame house in Devon

[Nickfromwales]

1 hour ago, JohnMo said:

Not correct. Woodcrete is an open structure and water will free flow under gravity out the bottom. It doesn't readily absorb water.

I have direct experience with both Velox and Isotex (both are woodcrete) and these blocks do harbour moisture, transmit it through the block, and are very different to use when stored dry vs left out in the elements. They do dry out, when kept dry though, but are like a coarse sponge vs a teabag. 

 

With woodcrete there was defo a presence / visible signs of moisture in the product within the dwelling, particularly on rainswept elevations, but not with EPS, at all.

 

Agree about free flowing under gravity, as that’s how water (rain) was getting inside the builds. It was notable on the lower 1/3 - 1/2 of the internal leaf, but was sopping at DPC. This was its worse at window and door reveals. 

The sub-contracted builder on that particular project was a very fussy chap too, so this wasn’t down to poor workmanship, quite the opposite in fact as in ‘it’ was getting a helping hand from

that chaps team; they were learning and mitigating as they went, to allow for such inadequacies, through his diligence and perseverance.

 

I’d say these types of builds should have the external rain-screen on asap.

 

Regarding EPS ICF, I have never seen the same, and I’ve been around enough of them. A brilliant product in comparison and will always be my go-to when a client approaches me with an enquiry and a preference to do an ICF build.

 

I'm also not a fan of the block having a bridges, or many bridges per block, capable of allowing air flow or moisture to wick, and with EPS ICF you don’t get either as the bridges are either EPS, synthetic, or stainless steel. 👌. 

 

 

[ToughButterCup]

Just for the record...

 

We have a few bits of Durisol left lying around uncovered and outside ( for at least 4 years). It's drizzling now, so the few blocks I have are wet. Tomorrow will be fine, so by lunchtime the face facing the sunshine will be dry. I'm considering using them to build the base of a static workbench. (Because the blocks will be filled with concrete and thus immovable). 

 

We have a piggery next to the house. 8 years after it's construction the piggery is still unclad. Exposed to the elements. It looks horrible. 

 

But it's bone dry.

 

Durisol is hydrophobic. The 'weave' of the fibers means that it's mostly made of air. 

Durisol is just like a Landrover: water flows out of it as fast as it flows in. 

[JohnMo]

2 hours ago, Nickfromwales said:

Velox and Isotex

Obviously Velox and Isotex are not very good copies of Durisol. So should not be compared as the same.

[jack]

20 hours ago, MCoops said:

Hi, I don't think they are - just the oak framing companies details, which is all over the web anyway. The previous docs are all on the planning portal also, so already in the public domain.

 

The document I referred to shows your name and the site address. If you're happy with that, no worries.

[Nickfromwales]

49 minutes ago, JohnMo said:

Obviously Velox and Isotex are not very good copies of Durisol. So should not be compared as the same.

Worse copies imho, as the block has way more woodcrete bridging between the external leaves to the internal ones, eg far more pathway for air / infiltration and obvs water / rain ingress etc.

 

I'm not posting negatively or argumentatively here because I woke up on the wrong side of the bed btw, these are actual, hands-on, real life experiences that I have had from gaining 1st hand experience, whilst physically being on these projects, and from being on site for the duration from pre-construction right through to completion.

 

I'd be interested to understand which of these manufacturers were early / late to the table too, before I suggested one copied another perhaps? The achievable U value with Velox, for eg, must be far in excess of both Durisol and Isotex, as the concrete core is completely enveloped in EPS, with just multiples of small cold bridges from the metal ties.

 

If you look at all 3 systems pragmatically then this is inarguable, by the design differences and not just my conclusions, and these are the fact based findings of myself, at least.

[MCoops]

20 hours ago, Alan Ambrose said:

>>> Yes, we are essentially building the house twice.

 

This gets trotted out fairly frequently on BH. So, conventional brick & block isn't? Something else covered with SIPs isn't? Yeah, don't worry about it if it works for you.

 

The other one usually raised is 'green oak expands contracts all over the place, how will you keep it airtight'?

 

Err, steel beams do this too, maybe steel doesn't have a great thermal expansion coefficient. Is this a problem in practice? So conventional softwood stick built doesn't move with moisture?

 

Green oak will move across its width but an irrelevant amount on length. It'll also settle down very quickly.

 

>>> We did speak to Oakwrights about it, but their costs were eye watering

 

FYI - I'm having sensible conversations with them re frame supply only. You can get a rough number for retail oak in £ / m^3 from online suppliers. (Last time I calculated it was £2.3K/m^3.) Then see how much the joint work and erection adds to the quoted price and check whether it's honest. I figure the oak frame guys should be charging about 3x the retail cost / m^2.

I'd never thought about Brick & Block like that - but yes, its essentially the same isn't it haha! Having the Oak solely on the inside means it can move all it likes really, adds to the character. All our airtightness is in the ICF walls and SIP roof. 

 

Glad you're making headway with Oakwrights, maybe we spoke to the wrong person there - or maybe they were busier then and not so much now, who knows. We've found a great local supplier and builder so we're happy enough. 

 

Hope it goes well for you when you start! 

[MCoops]

13 hours ago, Iceverge said:

 

Proper compression seals are key whatever you choose. Sliding seals don't work well . 

 

 

It's not solely a woodfiber issue. The houses I saw were EPS ICF. Amvic brand I think. 

 

Woodcrete is a different beast to woodfiber and I've never seen it in person. @JohnMo and @ToughButterCup have used it off the top of my head. 

 

In any case I would batten the ICF (before the pour to avoid drilling into concrete afterwards) and then fit cement board externally for to create a cavity for the rendered section. 

 

What's your plan for decorating inside the ICF? 

 

 

 

 

 

We've had a good chat with @ToughButterCup  Interesting you've seen it on EPS too, wonder what standard the build quality was done to. If they're on the mass new estates nothing would surprise me, they seem to go up so fast with so little care and consideration. 

 

Will definitely look into battening before fitting the cement board externally. Internally - well we were going to wet plaster originally as we'd planned on using Durisol, but we're a bit unsure on that now. Leaning more towards Nudura, which will need battening and boarding. Though we are thinking of lining with ply, we're not a fan of plasterboards - can't get the same fixing into them like you can masonry. Still a bit unsure on that side of things. Just trying to get the thing up and out the floor at the moment haha!

[MCoops]

13 hours ago, JohnMo said:

Not correct. Woodcrete is an open structure and water will free flow under gravity out the bottom. It doesn't readily absorb water.

 

Not sure where you are getting the information but it nothing like anything I experienced doing our build. Are you really talking about woodcrete ICF blocks or something different? Or wood fibre insulation?

 

 

@JohnMo Talking Durisol, ISOTEX type ICF blocks. Just from talking to people who have built with it and had problems. Everyone seems to have a different experience / opinion. Assuming your build went well? 

[ToughButterCup]

7 minutes ago, MCoops said:

...

Will definitely look into battening before fitting the cement board externally. Internally - well we were going to wet plaster originally as we'd planned on using Durisol, but we're a bit unsure on that now.

...

 

Think about airtightness too @MCoops.   Durisol is 80% ish air. So on my own, I rendered outside and in first ( and had the shoulder muscles to prove it ) 

Battened and boarded the wet room (+  tanking membrane (3) and tiles). Elsewhere plastered straight to the pre-rendered wall . BTW we found a plasterer who was a magician - needed to , the walls were all over the place(ish)

[MCoops]

@Nickfromwales Appreciate your experiences. It's not the first time I've heard them. The water issue seems to congregate at DPC level, and with so many bridges going from external to internal it seeps inside, particularly around opening as you say. So many people have said this - hasn't filled me with confidence.  I believe Durisol (Ecobrix) is the oldest block, but unsure on timescales on the others.

We do like the solidness of the woodcrete blocks, but the airtightness (or lack of) seems to be an issue to, with Ecobrix actually telling us we'd need to go and foam all the gaps up - which isn't really the point. 

It's an absolute minefield. Might just reinstate the cob barn 😂

[MCoops]

3 minutes ago, ToughButterCup said:

 

Think about airtightness too @MCoops.   Durisol is 80% ish air. So on my own, I rendered outside and in first ( and had the shoulder muscles to prove it ) 

Battened and boarded the wet room (+  tanking membrane (3) and tiles). Elsewhere plastered straight to the pre-rendered wall . BTW we found a plasterer who was a magician - needed to , the walls were all over the place(ish)

@ToughButterCup We have an almighty plasterer we found while renovating and have already t'd him up for the job, whatever that job ends up being. Worth their weight in gold plasterers! Hubby had a go once, never again haha! 

[JohnMo]

43 minutes ago, MCoops said:

@JohnMo Talking Durisol, ISOTEX type ICF blocks. Just from talking to people who have built with it and had problems. Everyone seems to have a different experience / opinion. Assuming your build went well? 

Durisol build - zero issues, 2 of us did the walls neither of us builders nor had either of us done it before.

 

38 minutes ago, MCoops said:

Durisol (Ecobrix) is the oldest block

Just after WW2, others 30+ year after.

 

39 minutes ago, MCoops said:

airtightness (or lack of) seems

If you are wet plaster inside that side is sorted. Render on outside that side is sorted. We lime/cement parged inside, very thin coat. Stone slips, and wooden cladding outside.

[JohnMo]

48 minutes ago, MCoops said:

Ecobrix actually telling us we'd need to go and foam all the gaps up

Well that won't make then airtight. Obviously the person doesn't understand airtightness.

[Nickfromwales]

1 hour ago, MCoops said:

well we were going to wet plaster originally as we'd planned on using Durisol, but we're a bit unsure on that now. Leaning more towards Nudura, which will need battening and boarding.

Nudura had a major advantage of being an 8’ long block which gives quicker lay time and straighter walls.

Annoyingly it’s a Canadian product ,so the inset nylon(?) fixing strips are at 405mm oc, so our metric 1200x2400mm stuff doesn’t work. Shame they can’t do a different stock model for the UK, but it may be we just don’t buy enough of it. 
 

Will need battening then board, unless you become inventive and are happy to stick the boards together and keep the joins away from the strips. Can be done, just an additional consideration when costing up the gross figures.

 

As far as wet plastering directly over woodcrete (if that’s what you’re referring to) then you’re in for a surprise as to just how hard that’ll be. On the Velox build there was an annex done first off, full wet plastering directly to the woodcrete, and required a lot of sets to get it ready to skim. Ended up around 30mm thick overall. 

The dried out walls had a visible crack around every single block, like the walls were painted over Lego. Took a lot of additional painting to deal with the enormous amount of locked in water that then sat in the woodcrete / bonding / skim etc, like best part of 6 months with heating and MVHR running. Not sure if they carried on displaying the cracks, but they were unhappy enough to take my advice and dot n dab the main residence. 
 

The unevenness in the cured woodcrete ICF was nowhere near close to taking a few sets of skim to a finish for paint. The sales patter may suggest this is easily achievable, but it ain’t. 👎.

 

The clients wallet was hit HARD, getting this to an acceptable finish. Very hard.

 

EPS ICF can be buffed out with surface rasps, and is very easy to rid of any undulations.

 

EPS cuts quickly and easily with a hot knife, but woodcrete is a PIG to chase or remove for services. I ended up using a 22mm SDS wood chisel and it took forever installing cables and pipes at the required safe depth.

[ToughButterCup]

4 minutes ago, Nickfromwales said:

...

The unevenness in the cured woodcrete ICF was nowhere near close to taking a few sets of skim to a finish for paint. 

...

 

 

Exactly right.

It's one of the many compromises made when choosing any build system. 

[Nickfromwales]

56 minutes ago, MCoops said:

I believe Durisol (Ecobrix) is the oldest block

Ok, thanks, I’d never asked the question, but interesting to see them how Isotex seem to have tried to limit the bridges. A very different block to the Durisol.

Velox different again as it is a totally separate internal leaf after concrete, this offering up the best option for an airtight build, but still needed a huge amount of time / labour / materials + liquid AT membrane (Passiv Purple) to parge and seal to airtight before dot n dabbing.

 

Just sooooo much additional work. 🤷‍♂️😵‍💫

[BotusBuild]

I have a blog on here outlining some experiences of our build with Nudura. Real self builders here.

All gone pretty well and very pleased with it. The imperial/metric issue Nick talks about above is a little annoying but we have dealt with it.

We have the outside rendered directly to the EPS using Nudura recommended render system. We are also partly stone cladding and partly wood cladding, and will end up with a couple of "steps" to contend with.

Overall, I would build with it again

[ToughButterCup]

7 minutes ago, Nickfromwales said:

..

The dried out walls had a visible crack around every single block, like the walls were painted over Lego. Took a lot of additional painting to deal with the enormous amount of locked in water that then sat in the woodcrete / bonding / skim etc, like best part of 6 months with heating and MVHR running. Not sure if they carried on displaying the cracks, but they were unhappy enough to take my advice and dot n dab the main residence. 

...

 

'... The dried out walls .... Took a lot of additional painting to deal with the enormous amount of locked in water ...'

Woodcrete ( as in 'Durisol' ) drains itself ...

 

Not one block outline is visible anywhere on the inside ( and parts of the outside) of our house. 

But in our piggery - even though its been rendered, you can see every single block. Because its not plastered or clad. (yet)

[Iceverge]

What sequence do you plan on building the oak frame and the ICF @MCoops? 

 

What comes first? 

[JohnMo]

17 minutes ago, Nickfromwales said:

EPS cuts quickly and easily with a hot knife, but woodcrete is a PIG to chase or remove for services. I ended up using a 22mm SDS wood chisel and it took forever installing cables and pipes at the required safe depth

If you want to chase walls woodcrete isn't your friend, as the woodcrete eats sharp teeth for breakfast, soon blunting them. I did the easy way, service gap with battens and plasterboard (dry lined). Battens are screwed directly in to woodcrete (through thin parge coat) with self drilling screws with a blob of sealant on them as they breakthrough the batten.

 

Only bit I didn't do was the plasterboard or taping/jointing.

 

Big polystyrene blocks are quicker and easier, but require suitable props and support y(they weren't available to us, as we are to far north), to hold it all together while the concrete is poured. Durisol needed a few bits of OSB screwed on at corners. Only thing hired in was adjustable props for the lintel forming.

 

All systems have pluses and minuses, choose what suits you. Various direct experiences of different systems offered, some I wouldn't touch with a barge pole, Durisol I would use again without issue. But would also look at polystyrene based ones as they offer airtight out of the box. But only if all the additional support structure were readily available.

 

Rebar not mentioned, Durisol needs very little, all the webs that @Nickfromwales doesn't like is one of the reasons for this apparently. I have rebar around openings and at a couple of high stress corners and that is about it.

[MCoops]

1 hour ago, Nickfromwales said:

 

...As far as wet plastering directly over woodcrete (if that’s what you’re referring to) then you’re in for a surprise as to just how hard that’ll be. On the Velox build there was an annex done first off, full wet plastering directly to the woodcrete, and required a lot of sets to get it ready to skim. Ended up around 30mm thick overall. 

The unevenness in the cured woodcrete ICF was nowhere near close to taking a few sets of skim to a finish for paint. The sales patter may suggest this is easily achievable, but it ain’t. 👎....

 

Wow, 30mm - that is something we definitely can't encounter as we have to spec the Oak frame to be xmm off the ICF wall - we were thinking to allow just a small gap, maybe 20mm, to allow a wet plaster skim behind, but will definitely look into this more and allow more wiggle room. 

[MCoops]

@Iceverge Plan is to get the Oak frame in place first. This is all being made off site so will just be craned in and fixed. Then the ICF walls will be built around the outside. Then the SIP roof panels will be added. 

We need to get the Oak out of the elements as quickly as we possible as the rain affects the finish, and obviously the drying out time increases the wetter it gets. 

[MCoops]

@JohnMoWe did wonder how easy it would be in reality to chase out the woodcrete. It doesn't look like the easiest thing to cut, though I've not tried yet. I do have a block though, I will test on. Durisol (Ecobrix) advised against battening and boarding as the wet plaster is needed to meet the air tightness. 

We do have all  the props available for EPS ones, but that is one plus point to woodcrete the fact these aren't needed. Though, everyone I've spoken to has had a blow out on their woodcrete pours - every chance this is user error though too, not necessarily the blocks. 

 

Thanks for your experience! 

[Russell griffiths]

7 minutes ago, MCoops said:

@Iceverge Plan is to get the Oak frame in place first. This is all being made off site so will just be craned in and fixed. Then the ICF walls will be built around the outside. Then the SIP roof panels will be added. 

We need to get the Oak out of the elements as quickly as we possible as the rain affects the finish, and obviously the drying out time increases the wetter it gets. 

Don’t worry about racing to get it in the dry. 
100% it will get wet, and 100% it will change colour because of this. 
you will need to clean the oak with oxalic acid when it’s all done to bring back the natural colour. 

[JohnMo]

5 minutes ago, MCoops said:

Durisol (Ecobrix) advised against battening and boarding as the wet plaster is needed to meet the air tightness

Again not correct.

 

You can parge coat (then mix of lime, cement, soft sand, mixed to a cream thickness) applied with a broom (and as in image) or you can do a membrane. We have almost no wet plasterers around us, so that wasn't an option.

 

is is