ICF How much more expensive ?

[saveasteading]

I did detailed cost comparisons for a 4 storey building, I think I've said before. All aspects included, eg other trades.

 

I wouldn't normally but the room size favoured eps for once, I thought, and I had been looking into it in detail. The ICF people said it was perfect and there would be a big discount for size.

 

The geometry was fixed, as was that the walls were brick faced, which you would think favoured cavity wall.

 

In best price order.

Timber kit.

Metal kit.

Steel frame. Stud internals.

Brick and block, beam and block floors.

Eps systems.

 

 

But that was for us, designing and constructing, with total design control. It may be a completely different order of costing for a small house and diy. Certainly the cash difference is less as a sum rather than %.

 

I'm a bit nervous about polystyrene blocks on a windy site.

 

 

 

[Iceverge]

1 hour ago, Dave Jones said:

 

im off the same conclusion, ICF kits need to be less than the price of celcons per m2  to be viable in anything but niche builds. Even then they will still be double/treble the cost as you need rebar, conc and an external finish.

 

I cant see an upside to them currently.

 

 

Why celcons and not normal 7N concrete blocks? 

 

The cost of blocks here pre labour is still only about €7/m2 per leaf.  Lightweight aerated blocks are about three times the price and only make the difference of a few mm of insulation. 

 

 

 

 

[Iceverge]

1 hour ago, Jenki said:

I've built 2 cabins on my site, and this is the first time I've built in a windy area,( built a fair few large extensions but never where wind was a constant thought during the build.)

It was a lightbulb moment building the cabins and the reality of trying to get good levels of airtightness was more of a concern. I'm sat here now and we've got a constant 20mph, with the odd 30 gust. 

I was surprised when at stick built stage how the wind was trying to push down the frame, when the OSB went on everything became more stable, but the wind blowing through any gap was surprising.

All of the above can be designed around, and detailed away, but all this comes at a financial and time cost.  The ICF route for me gives me a bit more security, it would be cheaper to build with block, but again the detailing if very important and most definitely not free.

We're cladding the building, brick facade is not a choice in this locality. It's wet dash, render or cladding.

It is definitely not stick it together and off you go, as you say the added rebar, and propping is required, but with stick built I would also have to prop during construction. But the benefit of putting it together, and once it's poured it's solid will give me a shorter time exposed to the elements. Time will tell, but that's the great (scary)  thing about self build.  🤣

 

Did you consider masonry with EWI? 

 

[Dave Jones]

2 minutes ago, Iceverge said:

 

Why celcons and not normal 7N concrete blocks? 

 

The cost of blocks here pre labour is still only about €7/m2 per leaf.  Lightweight aerated blocks are about three times the price and only make the difference of a few mm of insulation. 

 

 

 

 

 

not in England.

[Iceverge]

1 hour ago, SteamyTea said:

Airtightness and continuity of insulation.

 

Airtightness is all down to the junctions. This is common to all build types. If you do a good job of the penetrations and use wet plaster with masonry it's not rocket science. 

 

No reason you couldn't do a membrane and service cavity inside a masonry wall like a TF. It'd be a lot cheaper. 

 

I was worried about continuity of insulation with ours but the bonded beads filled every single nook and cranny. I test drilled some awkward places to check and had a good scan with the thermal camera too. 

 

 

[dpmiller]

5 minutes ago, Dave Jones said:

 

not in England.

what *is* the comparative cost then?

[Iceverge]

5 minutes ago, Dave Jones said:

 

not in England.

 

Standard blocks are about 70c here inc vat and aerated about €2-3. What's the price difference there? 

[SteamyTea]

Just now, Iceverge said:

use wet plaster with masonry it's not rocket science. 

Every place I have ever lived in that had plastered solid walls, all had cracks in them.

Some had bulging plaster.

So I would not think the long term airtightness is going to be brilliant. But no need to worry, people will quote the ACH figures from the testing date.

[Iceverge]

1 minute ago, SteamyTea said:

Every place I have ever lived in that had plastered solid walls, all had cracks in them.

Some had bulging plaster.

So I would not think the long term airtightness is going to be brilliant. But no need to worry, people will quote the ACH figures from the testing date.

 

We have some settlement cracks but I've filled them with sealant and painted over. At least I can see them. 

 

Time will tell about the overall airtighess. I would be curious to do another test in 10 years. There have been some suggestions of houses getting more airtight over time. This masonary house only got a worse score after 25 years due to the window seals. 

 

 

https://link.springer.com/article/10.1007/s12053-019-09781-3

 

 

[Jenki]

35 minutes ago, Iceverge said:

 

Did you consider masonry with EWI? 

 

I'm not quick enough to lay blocks,  adding external labour definitely doesn't make the sums work, then you still have to add the additional steps to make it airtight. It's all a balance, but for me the sums and time ICF seems to work. Only time will tell.

 

[saveasteading]

2 hours ago, Iceverge said:

2 hours ago, Dave Jones said:

 

not in England.

 

Standard blocks are about 70c here inc vat and aerated about €2-3. What's the price difference there? 

Today wickes are saying one dense block is £2.70, inc vat, aerated £2.60 and medium dense £3.25. Each. Obv that comes down a lot for quantity.

 

[Dave Jones]

1 minute ago, saveasteading said:

Today wickes are saying one dense block is £2.70, inc vat, aerated £2.60 and medium dense £3.25. Each. Obv that comes down a lot for quantity.

 

ouch.

 

paying just under £1 + vat

[JohnMo]

8 hours ago, Dave Jones said:

 

could you post a photo of the brickwork. Did you use a tiler or a brickkie ?

Did it myself, with the wife as additional labour.

 

 

[saveasteading]

33 minutes ago, Dave Jones said:

just under £1 + vat

That is because you don't have the freedom that Britain has to buy from wherever.  Oops. Politics

 

Seriously gb doesn't produce cement any more so it is imported.

Stone and sand aplenty though, so the rest of the cost must be higher wages, and profits, and prices from different sources remarkably similar.

 

Best price for lots of blocks is usually about the same as readymix. So may be about £1.50.

Perhaps others are more up to date on current prices.

 

[Jenki]

4 hours ago, saveasteading said:

I'm a bit nervous about polystyrene blocks on a windy site.

😬🙈. Me too. All insulation for that matter.

[saveasteading]

8 minutes ago, Jenki said:

polystyrene blocks on a windy site.

Are you allowed to build and fill in stages?

[JohnMo]

3 minutes ago, saveasteading said:

Are you allowed to build and fill in stages?

Interesting that is how you do Durisol, 6 levels at a time, fill 5.5 blocks, repeat.

[Jenki]

1 minute ago, saveasteading said:

Are you allowed to build and fill in stages?

Foundation course will be poured first, then I'll make a decision if I want to put all 4 course up before next pour. PolySteel have metal ribs t&g and clips that secure blocks to each other. So it's possible to use timber to screw the blocks to each other. You can use this timber for propping as well.  I intend to build my scaffold on the inside and use this to assist with bracing.

 

[saveasteading]

A downside of stages is in getting concrete delivered in small , and expensive , quantities.

And if you have outside labour, then that too.

 

Unless of course you mix your own on site, when the small stages make it less daunting.

I think on our project they were mixing 1m3 an hour with a domestic mixer. 

[Happy Valley]

We used Polysteel and braced from the inside by drilling into the slab. Had three concrete pours, ground floor, first floor then above once steels were in up to roof level. We attched pieces of ply to bits that we thought might be more vulnerable to a blow out. We didn't have any. Self tapping the stone/block ties into the steel frame made life easy for the builder.

 

With all that caging and rebar we used a piece of ply and hammer drills to ensure the concrete dropped to the bottom as you can't get an aerator in there.

 

 

Edited May 1, 2023 by Happy Valley

[saveasteading]

27 minutes ago, Happy Valley said:

as you can't get an aerator in there.

I am rather surprised that the kit has not been made to do this.

So I would seriously suggest to use the old 2 x 2 method of tamping. Just move a timber up and down in the concrete and it will mix and settle it, and remove air. It also merges the previous pour wit the new one, if soon enough and so loses a weak layer.

 

Looking at that picture, though, there are skinny vibrating pokers that should fit in there. Ask the plant hire company to get one in.

 

Wind speed at Wick is averaging 20km/h this week, up to 38km/h  (10m/s.).  That is windy.

I am thinking Happy Valley's support inside  and the scaffolding outside, wedged against the wall....and lots of stages.

 

Somebody earlier mentioned the wind during construction. The building will create increased wind speed and forces during construction, so all edges are vulnerable until all the openings are closed. Adding the roof before infilling windows also increases the forces.

It would be the same for timber of course, and it wouldn't be as heavy as concrete filled walls.

[Jenki]

2 hours ago, saveasteading said:

Wind speed at Wick is averaging 20km/h this week, up to 38km/h  (10m/s.).  That is windy.

It's calm now (5mph)😁, but we regularly see sustained winds of 20mph gusting 30.

[Jenki]

Just a quick update on my build, and the rebar, which initially was at over 3KM.  After chatting with Will at Poly steel, and the guy preparing the drawing for the certificate of design, there seemed to be large turning forces added to the walls, so the foundations (bedded on rock), were going to be huge to resist these forces.  The discussions resulted in the ICF walls being designed to stand on tier own ,not taking into account the Roof  structure? once the roof (fink trusses - and counter battens) were added  these turning forces (Moments) were eliminated, and the result will be  a more standard strip footing and a reduction of rebar by 50%.

A lesson that even though the cost of the ICF calculation were part of the ICF purchase, the disconnect between the two engineers could have cost considerable £££.   

[saveasteading]

Has anybody suggested bolting your footings to the rock?

Depends on the depth of course, but there is little point in breaking out granite and replacing with concrete.

[Dave Jones]

On 01/05/2023 at 14:15, saveasteading said:

I did detailed cost comparisons for a 4 storey building, I think I've said before. All aspects included, eg other trades.

 

I wouldn't normally but the room size favoured eps for once, I thought, and I had been looking into it in detail. The ICF people said it was perfect and there would be a big discount for size.

 

The geometry was fixed, as was that the walls were brick faced, which you would think favoured cavity wall.

 

In best price order.

Timber kit.

Metal kit.

Steel frame. Stud internals.

Brick and block, beam and block floors.

Eps systems.

 

 

But that was for us, designing and constructing, with total design control. It may be a completely different order of costing for a small house and diy. Certainly the cash difference is less as a sum rather than %.

 

I'm a bit nervous about polystyrene blocks on a windy site.

 

 

 

 

there is no way timber frame is cheaper than brick and block.