Brick & Block or ICF or Poured Concrete

[Shah]

Hello All,

 

Just want to get some opinions on what is best out of the above three building types? Some specific questions arise while researching the internet: Benefits/drawbacks

Concrete blocks with EWI

Fully fill cavity walls

Poured concrete walls with EWI

Which is more cost effective etc

 

Thanks,

Shah.

[Declan52]

Cheapest option will be the cavity wall. All the components are readily available and are of a standard nature.

Blocks with ewi while more simple to do as its not a standard method here it carries a specialist tag for no real reason so the render system and fixings tend to be more expensive. There was a post on Ebuild a while back where some one went through the different options for ewi and some of the prices where very high.

The concrete wall as it requires shuttering and steel will be the most expensive.

You shouldn't base your choice just on price but compare each one with regards the u values each system is likely to get you plus how much work is involved afterwards when you come to put in all the services and how you deal with airtightness. Each will have aspects that are better than the others. Also factor in can you get trades in to do the work locally or will you be paying higher labour costs due to the skills needed. 

What about timber frame ???

[K78]

I priced concrete block with ewi and cavity. Cavity is by far and away the cheapest.

 

You will also have less problems if you sell. 

 

EWI is ridiculously expensive in the uk and the render systems have a lot of issues IMO. 

[AliG]

I think a lot depends on who you are using to do the build both architect and builder and what they are used to working with.

 

I really wanted to do ICF, my architect had never used it but I persuaded him to try it. But then I couldn't find a reasonable quote to build it. It is advertised as a cheaper build but that wasn't the case when I looked into it.

 

In Scotland most self builds today seem to be SIPs, in England I am not so sure, maybe they are still mainly brick and block and as has been said that is probably the cheapest method.

 

The design of the house also comes into it. I was going to use SIPs after the ICF quote but the SE said that the spans were large and it would end up being full of steelwork so we went with Porotherm blocks. These are a thin joint block system which offers modestly better insulation, lightweight aircrete blocks are similar.

 

In terms of insulation, you can get a good wall U-Value with any method. Historically blockwork tended to have a 100mm cavity so only room for 50mm of insulation. I am having a 150mm cavity and 100mm of insulation as well as insulated plasterboard on the inside. You can get a good U-Value with any method it is usually just a matter of making the walls thicker. Similarly airtightness can be achieved via different methods for different builds. It is probably harder to fit insulation tightly in a cavity so it may not be as effective as it should be, full fill beads work well from that point of view but as they are EPS you need a large amount to get a good U-Value. I believe that they work out quite expensive.

 

I think the MBC twin wall timber frame a lot of people on here use looks very attractive from an insulation and value point of view. Personally I wanted concrete upper floors for a more solid feeling house so went with blocks.

 

I just checked, the actual outside walls are less than 5% of the build cost of my house. Especially on a larger build where the outside wall to volume ratio is low they won't move the needle much.

Edited October 6, 2016 by AliG

[Shah]

2 hours ago, Declan52 said:

Cheapest option will be the cavity wall. All the components are readily available and are of a standard nature.

Thank you Declan. You have used ICF for your build if I remember correctly from ebuild?

So how does the cavity wall system work? Can it be fully filled and how much insulation can be put in? What u values can be achieved?

 

2 hours ago, Declan52 said:

What about timber frame ???

I haven't looked into this as I would like a solid feel and I am conscious that I won't like it!

 

The thinking is to get a passive slab like JSH did with underfloor heating and then get the building started (be it brick/block, timber, concrete etc)

 

1 hour ago, K78 said:

 

I priced concrete block with ewi and cavity. Cavity is by far and away the cheapest.

 

Thanks, This is the trend I guess in terms of cost!

 

1 hour ago, AliG said:

I really wanted to do ICF

Thanks AliG. This is what I would like as well with a SIPs roof but I would like built in solar panels as well!!!

1 hour ago, AliG said:

You can get a good U-Value with any method it is usually just a matter of making the walls thicker.

This is what I am worried about. hence I was looking at EWI with concrete blocks so I could have 150mm of insulation with 150mm of blocks? Plus rend outside.

 

1 hour ago, AliG said:

Personally I wanted concrete upper floors for a more solid feeling house so went with blocks.

This! so what type concrete floor have you chosen?

Edited October 6, 2016 by Shah

[Declan52]

I went with block cavity as I could build it myself so saved money. The width of the cavity will determine the u value you end up with. The wider it is the more insulation you can get in so the lower the u value you end up with. You can also use lightweight blocks on the inside skin to improve the u value. Get the beads blown in if you go down that route instead of cavity boards/batts that the brickie build in as he goes.

Modern timber framed houses aren't the hollow echo build of the past. Yes the walls will be stud but with them being well insulated they are more solid. Plus you can use heavy type plasterboard like fermacell type sheets that will give you that solid feel.

[Shah]

Ah cool. I am thinking of as close to passive house (0.15 u value?) as possible. But I don't know if that would be easily achievable. How about ICC. Saw it on Viking house website. Would that be more expensive than the cavity wall although they are saying it is cheaper by like 20%. So not sure if someone has used this system on the forum or any information?

[Stones]

I'm building with ICF - have a skim through my blog. Certainly competitive with other forms of construction if you can find a contractor who is used to building with it (I was lucky in this respect, there being two ICF contractors up here). 

[Shah]

Great thanks @Stones will have a read through.

[Shah]

Just went through the blog @Stones. Very nice. I didn't understand why more insulation was stuck on rather than put into the existing form work? I have seen some companies provide wider plastic ties with extra insulation inserts... What other forms of cladding can be used (brick possible)?

[Stones]

Just the particular ICF product my builder uses. He has recently been on an awareness day for a system that puts the additional insulation inside the formwork, but the cost of that system is that much more that it still makes more financial sense for him to use the system he currently uses, even though it involves more on site labour. 

 

Cladding wise I guess you can fix on anything you want, including brick slips.

[Fallingditch]

I'm on the edge of floodzone 3a, so my preferred construction method was block and block, with EPS in a 200 cavity (for flood resilience).

 

To achieve airtightness, we used autoclaved concrete blocks (ytong) 100 outer and 215 inner, because they use thin bed cement and can be easily cut to shape.

 

Lightweight concrete also meant we didnt have to pile, and could go with an insulated reinforced concrete slab (so you dont need piling contractors and all the associated mess, but you do have spoil to get rid of)

 

The building is 10m x 8m and with room in gambrel roof. The gable wall reaches 10m high.

 

pros:

construction straightforward

easily handled and worked material 

should be very thermally efficient

 

 

cons

will not be as cheap as other methods (but I dever attemted to compare prices)

1st block laid on 29 April; last on 20th September (two layers and one labourer, installing easijoist floors on the way up), blocklaying goes on and on and on!

 

would I do it again?

Next time (if there is a next time) I would try to source a prefabricated, factory built house. Trouble is, its in Europe (for now) where the factories are, and Brexit has not helped the economics of sourcing pre-fabs from Europe.

Edited October 8, 2016 by Fallingditch
typo correction

[AliG]

I have Bison hollowcore floors in my current house and believe that I will be using the same ones in the new house. They haven't been ordered yet.

 

You give them the plans and the come precut to size and just sit on top of the blockwork.

 

They are absolutely fantastic, the kids can run around upstairs and you can't hear or feel anything.

 

The downsides are they are more expensive and they are a lot thicker as you cannot run services inside them. I have over 400mm between the ground and first floor. 200mm slabs, plus 100mm below and 110mm of insulation and screed above. Partly that is due to some 7m spans. If the max span was 6m they would use 150mm.

 

Also I have ended up with a very thick foundation slab due to the weight, at least that is what the SE said, I didn't go into the details. The internal ground and many of the first floor walls are blockwork as I have a second floor which is also concrete. The SE ended up specifying a 200mm thick floorslab.

 

150mm of full fill polystyrene beads is only going to give a U-Value of around 0.2. It would maybe fall to around 0.17 with aerated blocks. You would then need internal insulation to get down to 0.15.

 

I am using 100mm of Celotex CW4000 in a 150mm cavity and 25mm of internal insulation to get to 0.15 U-Value with Porotherm walls. The U-Value could be similar or better with lightweight blocks. You can also make the internal insulation thicker if you want a better U-Value.

 

I did briefly look into full fill with polystyrene beads. It wasn't clear if building control would allow it in Scotland. Full fill cavities are generally not allowed up here due to driving rain, you would probably have to persuade them it was not an issue, but it would probably be fine in England.

 

I guess the point is that you can achieve the kind of 0.15 U-Value you are looking for with a blockwork cavity wall and insulation and it is probably the cheapest and most substantial feeling building method.

 

When looking at insulation the walls sometimes don't make up that high a percentage of the outside envelope of the house. You should balance it with the roof, windows and floor. Personally I felt at 0.15 U-Value on the walls I could get better bang for my buck elsewhere. The roof is often the easiest place to gain insulation as unless you have a height restriction you can get a lot of insulation in there and achieve low U-Values relatively cheaply. Air tightness also often benefits heating costs more than U-Value especially in a larger house as you plan.

[Shah]

On ‎07‎/‎10‎/‎2016 at 12:33, Stones said:

Cladding wise I guess you can fix on anything you want, including brick slips.

That is good. I am leaning towards single skin inner with EWI and brick slips..

 

On ‎08‎/‎10‎/‎2016 at 10:31, Fallingditch said:

I'm on the edge of floodzone 3a, so my preferred construction method was block and block, with EPS in a 200 cavity (for flood resilience).

 

To achieve airtightness, we used autoclaved concrete blocks (ytong) 100 outer and 215 inner, because they use thin bed cement and can be easily cut to shape.

Why not just a single skin and then EWI?

 

On ‎08‎/‎10‎/‎2016 at 10:31, Fallingditch said:

Next time (if there is a next time) I would try to source a prefabricated, factory built house.

This would be very good as it will take much less time and the whole house can be designed and built away from site (probably will be much more expensive). Can you recommend any names?

 

On ‎08‎/‎10‎/‎2016 at 11:00, AliG said:

The downsides are they are more expensive and they are a lot thicker as you cannot run services inside them. I have over 400mm between the ground and first floor. 200mm slabs, plus 100mm below and 110mm of insulation and screed above. Partly that is due to some 7m spans. If the max span was 6m they would use 150mm.

How much more expensive? Any idea in terms of m2 cost comparison?

Yes that is one thick floor! Any other system which is a bit less thick (or design the house in a way to keep the spans less than 6 meters even still it will be still much thicker than traditional timber flooring)?

On ‎08‎/‎10‎/‎2016 at 11:00, AliG said:

I am using 100mm of Celotex CW4000 in a 150mm cavity and 25mm of internal insulation to get to 0.15 U-Value with Porotherm walls. The U-Value could be similar or better with lightweight blocks. You can also make the internal insulation thicker if you want a better U-Value.

I think Blocks/EWI/brickslips (render) or ICF/brickslips (render). This will keep the walls at a reasonable thickness with solid feel to it.

 

On ‎08‎/‎10‎/‎2016 at 11:00, AliG said:

The roof is often the easiest place to gain insulation as unless you have a height restriction you can get a lot of insulation in there and achieve low U-Values relatively cheaply. Air tightness also often benefits heating costs more than U-Value especially in a larger house as you plan.

What kind of roof system you are using? I was thinking of SIPs (with 200-300mm insulation) but they seem expensive. I also like to add in-roof solar panels.

Air tightness can be tackled by sand cement plaster on inside wall (probably with much ease ?).  

[AliG]

The concrete upper floors haven't come in with final quotes yet but are looking around £50 a square metre, hopefully less once the quotes are in.

 

But then you have the extra costs as the ceiling below has to be put on straps, the extra height meant I had more spoil removal from the site etc.

 

I didn't ever price up a posi-joist floor but it is possibly around half the price. Also I wanted under floor heating up the stairs, I am told this is still possible posi-joists, but it is a lot simpler on the concrete floor.

 

I believe that SIP roofs are expensive. My roof is made of small trusses and some straight rafters. The big cost is the PIR insulation. The original quote was astronomical using Kingspan. I changed to Celotex as they make 200mm insulation in one piece which can be cut between rafters. However, I am hoping to use 220mm Knauf Omnifit Stud plus insulated plasterboard underneath. It does not give quite as good a U-Value as Celotex, but is easier to fit and better from a noise and air tightness point of view, plus around a third cheaper again. I can't guarantee I am using it as so far it has proven almost impossible to buy in the UK despite being heavily advertised by Knauf.

 

[PeterW]

6 minutes ago, AliG said:

I believe that SIP roofs are expensive.

 

I was quoted £32k EX Vat for SIP panel roof that was 175mm panels so a uValue of 0.15...! Not surprisingly I didn't bother following it up !

[AliG]

The roof was one one of the things that made my ICF quote really expensive. I just got it out again. The quote was £150k for just EPS panels, no steel, battens etc. It is more than 50% more than the roof I am building which has a better U-Value.

 

Actually looking back at the ICF quote, the roof, foundations and walls all cost around 50% more than what I am doing now. They also had very poor U-Values. The EPS used inICF systems has a lot worse R-Value than PIR insulation and the walls have to be very thick to get a 0.15 U-Value, probably similar to my 420mm thick walls.

[Fallingditch]

10 hours ago, Shah said:

Why not just a single skin and then EWI?

 

Excellent question. That would have been the sensible thing (as long as you like render finishes as I do).

 

However when I applied for Planning Permssion for a 3 storey replacement house in the countryside, I decided I had t make it look like a nearby Water Mill, so the application was for a building clad in white weatherboard. I was very glad to be granted permission with few conditions (and I didn't want to risk reapplying).So then we had to work out how to hold the cladding up - and the outcome of that was 'build a second skin in 100mm. Pain in the neck and with a big price tag.

 

Re suppliers of prefab houses: I will have to dig out the details - but please note I cannot recommend any of them

 

[Shah]

12 hours ago, AliG said:

The concrete upper floors haven't come in with final quotes yet but are looking around £50 a square metre, hopefully less once the quotes are in.

 

But then you have the extra costs as the ceiling below has to be put on straps, the extra height meant I had more spoil removal from the site etc.

Cool thanks for this. I am just worried about the extra thickness between floors which could be avoided (maybe not as for longer spans for posi joists).

Is there a system where there could be service void in the floor to save on the extra height?

 

12 hours ago, AliG said:

I believe that SIP roofs are expensive. My roof is made of small trusses and some straight rafters. The big cost is the PIR insulation. The original quote was astronomical using Kingspan.

 

12 hours ago, PeterW said:

I was quoted £32k EX Vat for SIP panel roof that was 175mm panels so a uValue of 0.15...! Not surprisingly I didn't bother following it up !

So SIP is out of the question!! What is the best way to reduce thermal bridge as well as have 0.15 u value of roof? If roof space were to use as a bedroom etc what would be best?

 

12 hours ago, AliG said:

Actually looking back at the ICF quote, the roof, foundations and walls all cost around 50% more than what I am doing now. They also had very poor U-Values. The EPS used inICF systems has a lot worse R-Value than PIR insulation and the walls have to be very thick to get a 0.15 U-Value, probably similar to my 420mm thick walls.

Wow that is expensive. Those are thick walls.

11 hours ago, Fallingditch said:

Excellent question. That would have been the sensible thing (as long as you like render finishes as I do).

I am no fussed and would go for the best and cost efficient way to build. If planners ask for brick finish then maybe brick slips could be used on render? How much extra cost would this be (any idea)?

 

11 hours ago, Fallingditch said:

So then we had to work out how to hold the cladding up - and the outcome of that was 'build a second skin in 100mm. Pain in the neck and with a big price tag.

Well in that case cavity wall works best for you.

[PeterW]

57 minutes ago, Shah said:

What is the best way to reduce thermal bridge as well as have 0.15 u value of roof? If roof space were to use as a bedroom etc what would be best?

 

Standard build up of 190mm joist full fill with a rock wool product plus 40mm of PIR under the rafters gets you there and it also means you have a VCL with the foil. 

 

I plan to do 2 layers of 25mm insulation with a cross batten and counter batten which leaves a cold bridge of around 0.064% which I think I can cope with ... 

[Shah]

3 hours ago, PeterW said:

Standard build up of 190mm joist full fill with a rock wool product plus 40mm of PIR under the rafters gets you there and it also means you have a VCL with the foil.

Cool. Air tightness easy to achieve with this system?

[PeterW]

"Technically" if you ensure all foil joins are done correctly, and the wall to roof join is done correctly then yes, you have an airtight build.

 

The devil is in the detail !

[AliG]

Similar to my roof. It seems one of the easier places to achieve a good U-Value without it affecting the design. Using the roof space shouldn't be an issue, indeed insulation between rafters lends itself much more easily to using the space.

[nod]

On ‎06‎/‎10‎/‎2016 at 15:41, Shah said:

 near Hello All,

 

Just want to get some opinions on what is best out of the above three building types? Some specific questions arise while researching the internet: Benefits/drawbacks

Concrete blocks with EWI

Fully fill cavity walls

Poured concrete walls with EWI

Which is more cost effective etc

 

Thanks,

Shah.

The house I'm about to construct is two layers of block 125 cavity full fill Block and beam floor

I didn't expect to be anywhere near a timber frame build with the sap count

But was quite surprised to find out that I am 29% over the sap count pass