ICF

[SteamyTea]

Seems to me that ICF is getting mentioned quite a bit.

Why is this?

 

Seems that a lot of people like the system, but there have been a lot of problems with it as well.

 

So it is about time that we dis a proper critique of it, may save a lot of tears.

[JohnMo]

I'll start off

Durisol

Advantages

1. Easy to DIY, just read the installer manual and/or go on the course.  I did mine at the height of COVID, so no training available. No issues I just read the manual.  If you one of those that knows better than reading a manual, the product is not for you.

2. Pretty good U value out of the box 0.14, for the 365mm thick block.

3. No special tools or props, or support system required, except adjustable props at the opening (ease and cheap hire locally)

4. Vapour open breathable walls, remains so with a cement/lime parge coat, while becoming airtight.

5. Little or no thermal bridges

6. Can build in just about any weather and pour concrete at just about UK temperature - well in the minus temperatures.

7. Didn't that much rebar, when compared to other systems.

 

Disadvantages

1. Not air tight so a large coat or similar required internally.

2. Blocks are not fully square due the the tapers in the moulds.  Once you realise it's easy to make allowances.

3. Only 6 rows of blocks high between concrete pours

 

Some say during the build the house will get flooded as the they are open to water entry - our build started November and windows weren't in until April, we had no issue with water getting in after the roof was on. We also had 2 walls open and not covered externally for approx 2 years with no issue. 

 

[SteamyTea]

8 minutes ago, JohnMo said:

I'll start off

Good start, thanks.

[Ajn]

13 minutes ago, JohnMo said:

Some say during the build the house will get flooded

Well yes and no. We had problems with the weather side wall. Heavy rain at an angle of 45deg didn't come in it just ran off until it hit the dpc then came in. Not a lot but if we didn't have to have the dpc then it would be no problem.

 

Durisol will not hold water in any form and would work without a dpc.

 

Key tips though.

1. don't let a builder anywhere near it.

2. a battery grinder is good for removing the odd nib as you lay them.

3. Use string that is not bent for your lines

 

 

[ToughButterCup]

Here's what I have written about Durisol.

There are 189 hits on this search  (Search> Durisol > author search> @ToughButterCup ) - so I think it's fair to say I know my way around a Durisol block. 

 

I have made every single error there is to make on the system, from simple sloppiness, to under-ordering -  to allowing a complete wall collapse. Blow-outs, some spectacular, others piffling.

But it's hard to  separate my initial incompetence and naivete from the merits or otherwise of the build system.

 

I now - after eight years with the stuff - have absolutley no doubt whatever that an experienced builder who has built a few houses in the system can build a very airtight, highly insulated house with Durisol. No doubt at all.

 

The principal issue is that the system is marketed as suitable for first-time - (and likely once only builders) 

I was (but am no longer) the very weak link in the chain .

 

The cost of that experience has been bourne by my long-suffering family who have constantly believed in me, grinned and bore the substantial errors and ommissions, and continue to sing 

 

 

[SteamyTea]

34 minutes ago, ToughButterCup said:

have made every single error there is to make on the system,

To make it easy, a short list here may be helpful to others.

And don't forget to mention the bracing.

[Jenki]

My experience is currently 0, but will rapidly change from Wednesday when I take delivery of my PolySteel blocks.

Why I changed to ICF.

1, My location is windy, exposed, costal.

2, The cost of insulation ( wool batts / wood fibre) has gone astranomical.

Added to the cost of tapes/ membranes for airtightness.

3, I can use the PolySteel block underground so removes cold bridges and is cheaper than an insulated raft. This eliminates the DPC, as the core is continuous

 

4, Scotland as of February require a U of 0.15 for walls. The PolySteel blocks don't meet this on there own. So need EWI / IWI. A negative 

 

5, PolySteel have a metal grid and firings at 150mm centres to allow you to screw EWI/ IWI , battens, plasterboard etc. 

They clip together, and have T&G on all edges, making them very robust, and blowouts, as far as I can tell are rare.

Wall Air tightness is guaranteed.

6, My costings to build with ICF compared to Timber frame, with the same U values / airtightness are similar, I think ICF will cost me around 3k more, but I am  saving on the foundation cost so this come down to 1.5k. And I doubt I would achieve the same airtightness with timber frame.

7 lastly, the process will be quicker. And I only have a short "long day" season so speed is good to try to get watertight for winter.

 

[FM2015]

Personally, rather than being brand specific, people who want an ICF build should be looking at the following:

1. Big one first, work with a warranty provider and lender who know about ICF. They will provide a steer.

2.  Achieving latest sap regs does put emphasis on the walls achieving a certain wall value but sap is about the building as a system not a collection of discrete entities

3.diy or subcontractors.  The same products don't necessarily apply due to experience Vs simplicity of product.  Someone is still stacking a liquid vertically

4.  Price point/performance

5.whole system cost.  What additional benefits, cost, materials, labour does a product provide once built?  Some icfs need battening off, others don't.  Airtightness, window finishing, exterior finishing.  It's not just about the blocks.

 

I'm always going to lean towards eps/XPS based systems installed by a professional simply because pouring and pumping concrete IS dangerous and often it is experience which is the key mitigator.  Yes, I am also in the trade but diyers are going to DIY, so they should appreciate the risks.

 

 

[FM2015]

Adding to the above.

 

Understanding that ICF is part of a wall system not the whole thing when it comes to structural warranties.

 

Not all ICF systems can be covered by all renders for example.  Different ICFs have different conditions for cladding, and different cladding attracts different warranty conditions.