ICF - a list of questions/thoughts

[mjward]

Hello

 

After making the decision quite early on to go down the ICF route, the Self Build show in Swindon last weekend was my first experience up close. The good thing is, after seeing the various types first hand, reading the 120+ page Durisol online how-to guide, plus several hours of YouTube videos, I've now got the confidence to build myself whereas prior to the show the plan was to get builders to hand over the shell. 

On to more important things...questions for those that have done this or are looking into it:

 

1) The woodcrete manufacturers had the "no bracing needed" pitch. However, once you read the guides, it is very much needed around openings, corners and wherever you've cut into the blocks. Fair enough but for those that have gone the woodcrete route (e.g. Isotex/Durisol) was that the only bracing you required in the real world?

 

2) another woodcrete pitch was that the whole wall is a viable mounting point for cabinets etc, vs polystyrene ICF needing to line up cabinets (or plasterboard batons) to certain points. I can easily see why that is possible for low/floor sitting cabinets, but does that hold true for TVs and wall mounted cabinets?

 

3) Pipes/services...which of these (if any) need to be cut in pre-pour? I'm guessing due to diameter, waste pipework pre-pour would make life a lot easier, but do you need conduits for the other services or simply cut in post?

 

4) regardless of ICF product, are people using that same ICF for their foundations or are there cost savings by moving to a pre-formed block etc?

 

5) for the DIYers... how long did it take you to assemble your ICF blocks ahead of the pour? (be super useful to have idea of no. of people helping + sqm/ft of the floor)

 

6) at the show I noticed that rebar was only used to help form lintels whereas some of the YouTube videos for the same manufacturers showed them being used for the full course of the build. Is this just a geographic thing, i.e. not needed in UK as this isn't earthquake country or is rebar needed in more places than just the window/door openings?

 

7) I came across a new "thing" at the show and that was brick slips. I like the idea that this can be stuck directly on the exterior of the woodcrete ICF blocks by a competent DIYer however with all things I'm not familiar I am not wholly comfortable with them at this stage. Does anyone have information/experience with their longevity?  Will they remain stuck on that wall for 50+ years? From a cost perspective, any ballpark figures for a full brick + labour external wall onto the woodcrete vs slip per sqm/ft? There are many things you try and save money on when building a house and many things you don't, I'm just trying to ascertain if the slip (DIY and less material cost) is a more efficient route than brick (thick/higher thermal efficiency & stronger/longer lasting)

 

8 ) again the curse of YouTube... I have noticed on some videos that the builders are adding an additional layer of insulation on the outside of the ICF and then cladding the whole thing. Is that just for those in Alaska or potentially needed in a UK build too?

 

9) Internal walls...do people continue with the ICF product or switch to breeze block etc? what would sway the decision other than cost?

 

10) Joists...looks like the wall plate is the best option, the put the joint hangers directly onto that. With the large bolts for the wall plate, are people fitting those pre-pour so that the concrete cures around the bolt or drilling into the concrete afterwards?

 

11) Sound insulation... read quite a few articles on this but I always think you can't take the product in isolation (i.e. in real world depends on your doors, floors, ceilings etc). However, for those that have ICF, is there a noticeable lack of sound transmission? I would like to design the cinema room to be next to the kitchen (where it is in our current house) but I've been warned that it could be divorce inducing if the sound rattles through the kitchen as much as it does now!

 

Think that's all I've got for now, apologies for the long post but just thought for other users it might be useful to have this and subsequent responses as a reference. Thanks in advance. 

 

Martin 

[Pm1987]

36 minutes ago, mjward said:

On to more important things...questions for those that have done this or are looking into it:

 

1) The woodcrete manufacturers had the "no bracing needed" pitch. However, once you read the guides, it is very much needed around openings, corners and wherever you've cut into the blocks. Fair enough but for those that have gone the woodcrete route (e.g. Isotex/Durisol) was that the only bracing you required in the real world?

We used Durisol and braced the corners and vertically ever couple of meters. I didn't have the bottle to pour the maximum height suggested by dursol and generally poured ever 1.5m - 2m.The openings are a simple box around the opening we used scaffold boards with props in the centre. 

36 minutes ago, mjward said:

 

2) another woodcrete pitch was that the whole wall is a viable mounting point for cabinets etc, vs polystyrene ICF needing to line up cabinets (or plasterboard batons) to certain points. I can easily see why that is possible for low/floor sitting cabinets, but does that hold true for TVs and wall mounted cabinets?

We used batons inside to allow for service voids. I think it will take you just as long to trace the walls for cables etc but could be wrong. The block is very easy to attach onto with wood screws. 

36 minutes ago, mjward said:

 

3) Pipes/services...which of these (if any) need to be cut in pre-pour? I'm guessing due to diameter, waste pipework pre-pour would make life a lot easier, but do you need conduits for the other services or simply cut in post?

Ours went through the foundations. We had to core some small holes for the air source and lighting cables but this again was pretty simple. I felt it was easier to drill the block rather than try to allow holes through beforehand.

36 minutes ago, mjward said:

 

4) regardless of ICF product, are people using that same ICF for their foundations or are there cost savings by moving to a pre-formed block etc?

 

5) for the DIYers... how long did it take you to assemble your ICF blocks ahead of the pour? (be super useful to have idea of no. of people helping + sqm/ft of the floor)

 

We started the ICF build in Mid / Late Aug 2019 and completed the last pour in middle of Nov. This was myself and a mate who worked full time and had about two week annual leave. The house is 18m x 8m (ground and first floor).

36 minutes ago, mjward said:

 

6) at the show I noticed that rebar was only used to help form lintels whereas some of the YouTube videos for the same manufacturers showed them being used for the full course of the build. Is this just a geographic thing, i.e. not needed in UK as this isn't earthquake country or is rebar needed in more places than just the window/door openings?

Due to me being close to a MOD site we had specialist blast loadings applied to the house (not through choice) which meant we had to have rebar 250mm centres horizontally and vertically around the whole external walls. This was onto of the rebar used within the lintels. 

36 minutes ago, mjward said:

7) I came across a new "thing" at the show and that was brick slips. I like the idea that this can be stuck directly on the exterior of the woodcrete ICF blocks by a competent DIYer however with all things I'm not familiar I am not wholly comfortable with them at this stage. Does anyone have information/experience with their longevity?  Will they remain stuck on that wall for 50+ years? From a cost perspective, any ballpark figures for a full brick + labour external wall onto the woodcrete vs slip per sqm/ft? There are many things you try and save money on when building a house and many things you don't, I'm just trying to ascertain if the slip (DIY and less material cost) is a more efficient route than brick (thick/higher thermal efficiency & stronger/longer lasting)

 

8 ) again the curse of YouTube... I have noticed on some videos that the builders are adding an additional layer of insulation on the outside of the ICF and then cladding the whole thing. Is that just for those in Alaska or potentially needed in a UK build too?

 

9) Internal walls...do people continue with the ICF product or switch to breeze block etc? what would sway the decision other than cost?

Our internal walls downstairs are durisol which we poured at the same time as the external walls. Originally the engineer had them planned for the upstairs walls (not sure if durisol were giving him a little bung) but these were changed to timber partitions as easier and quicker to install.

36 minutes ago, mjward said:

 

10) Joists...looks like the wall plate is the best option, the put the joint hangers directly onto that. With the large bolts for the wall plate, are people fitting those pre-pour so that the concrete cures around the bolt or drilling into the concrete afterwards?

Wall plate as you said with the plate installed prepour and the concrete setting around them. 

36 minutes ago, mjward said:

 

11) Sound insulation... read quite a few articles on this but I always think you can't take the product in isolation (i.e. in real world depends on your doors, floors, ceilings etc). However, for those that have ICF, is there a noticeable lack of sound transmission? I would like to design the cinema room to be next to the kitchen (where it is in our current house) but I've been warned that it could be divorce inducing if the sound rattles through the kitchen as much as it does now!

 

Think that's all I've got for now, apologies for the long post but just thought for other users it might be useful to have this and subsequent responses as a reference. Thanks in advance. 

 

Martin 

 

[Conor]

1 hour ago, mjward said:

Hello

 

After making the decision quite early on to go down the ICF route, the Self Build show in Swindon last weekend was my first experience up close. The good thing is, after seeing the various types first hand, reading the 120+ page Durisol online how-to guide, plus several hours of YouTube videos, I've now got the confidence to build myself whereas prior to the show the plan was to get builders to hand over the shell. 

On to more important things...questions for those that have done this or are looking into it:

 

1) The woodcrete manufacturers had the "no bracing needed" pitch. However, once you read the guides, it is very much needed around openings, corners and wherever you've cut into the blocks. Fair enough but for those that have gone the woodcrete route (e.g. Isotex/Durisol) was that the only bracing you required in the real world?

 

2) another woodcrete pitch was that the whole wall is a viable mounting point for cabinets etc, vs polystyrene ICF needing to line up cabinets (or plasterboard batons) to certain points. I can easily see why that is possible for low/floor sitting cabinets, but does that hold true for TVs and wall mounted cabinets?

 

3) Pipes/services...which of these (if any) need to be cut in pre-pour? I'm guessing due to diameter, waste pipework pre-pour would make life a lot easier, but do you need conduits for the other services or simply cut in post?

 

4) regardless of ICF product, are people using that same ICF for their foundations or are there cost savings by moving to a pre-formed block etc?

 

5) for the DIYers... how long did it take you to assemble your ICF blocks ahead of the pour? (be super useful to have idea of no. of people helping + sqm/ft of the floor)

 

6) at the show I noticed that rebar was only used to help form lintels whereas some of the YouTube videos for the same manufacturers showed them being used for the full course of the build. Is this just a geographic thing, i.e. not needed in UK as this isn't earthquake country or is rebar needed in more places than just the window/door openings?

 

7) I came across a new "thing" at the show and that was brick slips. I like the idea that this can be stuck directly on the exterior of the woodcrete ICF blocks by a competent DIYer however with all things I'm not familiar I am not wholly comfortable with them at this stage. Does anyone have information/experience with their longevity?  Will they remain stuck on that wall for 50+ years? From a cost perspective, any ballpark figures for a full brick + labour external wall onto the woodcrete vs slip per sqm/ft? There are many things you try and save money on when building a house and many things you don't, I'm just trying to ascertain if the slip (DIY and less material cost) is a more efficient route than brick (thick/higher thermal efficiency & stronger/longer lasting)

 

8 ) again the curse of YouTube... I have noticed on some videos that the builders are adding an additional layer of insulation on the outside of the ICF and then cladding the whole thing. Is that just for those in Alaska or potentially needed in a UK build too?

 

9) Internal walls...do people continue with the ICF product or switch to breeze block etc? what would sway the decision other than cost?

 

10) Joists...looks like the wall plate is the best option, the put the joint hangers directly onto that. With the large bolts for the wall plate, are people fitting those pre-pour so that the concrete cures around the bolt or drilling into the concrete afterwards?

 

11) Sound insulation... read quite a few articles on this but I always think you can't take the product in isolation (i.e. in real world depends on your doors, floors, ceilings etc). However, for those that have ICF, is there a noticeable lack of sound transmission? I would like to design the cinema room to be next to the kitchen (where it is in our current house) but I've been warned that it could be divorce inducing if the sound rattles through the kitchen as much as it does now!

 

Think that's all I've got for now, apologies for the long post but just thought for other users it might be useful to have this and subsequent responses as a reference. Thanks in advance. 

 

Martin 

2. You'll want to be going through to the concrete for anything like kitchen cabinets, TV, heavy shelving etc. The plastic webs in poly off are evenly spaced and easy to find.

 

3. If you know EXACTLY where you're services will be going through, then yes, stick a bit of ducting in pre pour. I did this for electric and water, but not for my MVHR or ASHP pipes as they are not confirmed yet. Otherwise, you'll be core drilling after the pour, but in exactly the right spot.

 

4. Your foundation system will depend on your ground conditions and the engineer's preferred design. We did a concrete raft and ICF started directly on this. Same can be done for trench founds, speeds things up and reduces cold bridging.

 

5. our builder needed a full week for our 100m2 footprint.

 

6. Rebar and concrete mix will be determined by your engineer. Our build needed 2 verticle rows of 10mm bar every 200mm in the basement, and 1 row of 10mm bar every 400mm for the rest of the building. 10mm lateral bars every 1200mm. Each openings requirements will depend on the spans and imposed loadings. E.g we have a floating corner that needs 32mm bar!

 

8. We're adding an additional 50mm insulation to our standard Amvic blocks to get to u0.15 for passive House standards. It's far easier and cheaper to add PIR insulation to the inside of the walls rather than EPS to the outside. Can be done DIY over a weekend. Whereas external requires scaffolding, thicker sheets of EPS and lots and lots of big screws. You just need to factor in this loss of space in your design.

 

9. Using ICF for internal walls eats up a huge amount of space (e.g. 280mm Vs 100mm) compared to single block or stud walls. And costs a lot more. Bit it is faster and DIY able.

 

One thing I would add, if you are doing this DIY, advise you to try and visit a build where it is happening. Also, you'll need to get your own structural warranty organised of not using a contractor. Factor in another £3k for that.

Edited October 21, 2020 by Conor

[willbish]

 

4 hours ago, mjward said:

3) Pipes/services...which of these (if any) need to be cut in pre-pour? I'm guessing due to diameter, waste pipework pre-pour would make life a lot easier, but do you need conduits for the other services or simply cut in post?

I sleeved MVHR prior to pour. Everything else has been drilled through after. If you can, design out waste pipes going through the exterior wall and send them all down through the slab.

 

4 hours ago, mjward said:

4) regardless of ICF product, are people using that same ICF for their foundations or are there cost savings by moving to a pre-formed block etc?

Insulated raft for foundation, works really well with ICF

 

4 hours ago, mjward said:

5) for the DIYers... how long did it take you to assemble your ICF blocks ahead of the pour? (be super useful to have idea of no. of people helping + sqm/ft of the floor)

Blocks arrived 26/03/19, first pour 29/04/19 to 2.8m. Just me. Also working day job 50% of the time. So 18 days for groundfloor 88m2.

 

 

 

4 hours ago, mjward said:

6) at the show I noticed that rebar was only used to help form lintels whereas some of the YouTube videos for the same manufacturers showed them being used for the full course of the build. Is this just a geographic thing, i.e. not needed in UK as this isn't earthquake country or is rebar needed in more places than just the window/door openings?

Yes you've got it. Vertical rebar for any retaining walls

 

4 hours ago, mjward said:

8 ) again the curse of YouTube... I have noticed on some videos that the builders are adding an additional layer of insulation on the outside of the ICF and then cladding the whole thing. Is that just for those in Alaska or potentially needed in a UK build too?

Potentially for UK too. I think it makes it more economical to buy a standard ICF product then add additional insulation. And cutting 200mm ICF blocks is a no fun.

 

4 hours ago, mjward said:

9) Internal walls...do people continue with the ICF product or switch to breeze block etc? what would sway the decision other than cost?

Didnt even consider ICF for the internals, too costly, waste of insulation. I went with 100mm concrete block.

 

4 hours ago, mjward said:

10) Joists...looks like the wall plate is the best option, the put the joint hangers directly onto that. With the large bolts for the wall plate, are people fitting those pre-pour so that the concrete cures around the bolt or drilling into the concrete afterwards?

Yes pole plate with bolts cast into the concrete. If I was doing it again I think I would drill and resin. Fixing a pole plate to EPS and then pouring concrete behind resulted in a little more movement than I was happy with. Has been made good now but was a bit of effort.

 

 

[mjward]

22 hours ago, Pm1987 said:

We used Durisol and braced the corners and vertically ever couple of meters. I didn't have the bottle to pour the maximum height suggested by dursol and generally poured ever 1.5m - 2m.The openings are a simple box around the opening we used scaffold boards with props in the centre. 

 

Sounds sensible. I suspect the cost of the extra pours is negligible vs the it going wrong scenario if you build too high

 

22 hours ago, Pm1987 said:

We used batons inside to allow for service voids. I think it will take you just as long to trace the walls for cables etc but could be wrong. The block is very easy to attach onto with wood screws. 

 

Did you baton all walls or just for services? Was wondering about thermal efficiency with the void vs dot and dab.

 

22 hours ago, Pm1987 said:

Ours went through the foundations. We had to core some small holes for the air source and lighting cables but this again was pretty simple. I felt it was easier to drill the block rather than try to allow holes through beforehand.

 

makes sense i.e. pre-plan for the larger intrusions but don't fret if you have to cut anything post 

 

22 hours ago, Pm1987 said:

 

We started the ICF build in Mid / Late Aug 2019 and completed the last pour in middle of Nov. This was myself and a mate who worked full time and had about two week annual leave. The house is 18m x 8m (ground and first floor).

 

Thanks for this. Seems at the higher end of what I've seen but I will take from your pour figures that you are similar to me and would rather take a bit more time if it means getting it right!

 

22 hours ago, Pm1987 said:

Due to me being close to a MOD site we had specialist blast loadings applied to the house (not through choice) which meant we had to have rebar 250mm centres horizontally and vertically around the whole external walls. This was onto of the rebar used within the lintels. 

 

Was wondering why your blocks looked so much bigger to what I had seen

 

22 hours ago, Pm1987 said:

Our internal walls downstairs are durisol which we poured at the same time as the external walls. Originally the engineer had them planned for the upstairs walls (not sure if durisol were giving him a little bung) but these were changed to timber partitions as easier and quicker to install.

 

I'm thinking solid internal walls for both ground and first floor (sound/strength angle) so I suspect I either do both via ICF or standard breeze block. Most pictures I've seen have builders using breeze for the internal so guessing a noticeable price difference but given the DIY approach I wonder if for me it will net out to much of a change and thus easier to ICF the lot.

 

22 hours ago, Pm1987 said:

Wall plate as you said with the plate installed prepour and the concrete setting around them. 

 

 

Perfect, that clears that up thank you!

[mjward]

22 hours ago, Conor said:

2. You'll want to be going through to the concrete for anything like kitchen cabinets, TV, heavy shelving etc. The plastic webs in poly off are evenly spaced and easy to find.

 

Does that just apply to the polystyrene ICF or woodcrete too?

 

22 hours ago, Conor said:

3. If you know EXACTLY where you're services will be going through, then yes, stick a bit of ducting in pre pour. I did this for electric and water, but not for my MVHR or ASHP pipes as they are not confirmed yet. Otherwise, you'll be core drilling after the pour, but in exactly the right spot.

 

I've rich in time so I'm hoping to plan as much as possible so can get details like this sorted but as you say, anything I miss or need to change I can core drill after

 

22 hours ago, Conor said:

 

4. Your foundation system will depend on your ground conditions and the engineer's preferred design. We did a concrete raft and ICF started directly on this. Same can be done for trench founds, speeds things up and reduces cold bridging.

 

As per the Pm1987 I think you guys are steering me in the right direction. I'm new to a concrete raft so will do some googling but sounds like that pairs well with an ICF build (assuming a suitable ground)

 

22 hours ago, Conor said:

 

5. our builder needed a full week for our 100m2 footprint.

 

Speedy gonzales!! awesome work

 

22 hours ago, Conor said:

 

6. Rebar and concrete mix will be determined by your engineer. Our build needed 2 verticle rows of 10mm bar every 200mm in the basement, and 1 row of 10mm bar every 400mm for the rest of the building. 10mm lateral bars every 1200mm. Each openings requirements will depend on the spans and imposed loadings. E.g we have a floating corner that needs 32mm bar!

 

Roger that, so essentially for the DIYer it's not one to fret about as guidance on it/direction will come from the engineer. 

 

22 hours ago, Conor said:

 

8. We're adding an additional 50mm insulation to our standard Amvic blocks to get to u0.15 for passive House standards. It's far easier and cheaper to add PIR insulation to the inside of the walls rather than EPS to the outside. Can be done DIY over a weekend. Whereas external requires scaffolding, thicker sheets of EPS and lots and lots of big screws. You just need to factor in this loss of space in your design.

 

How do this now look from a mounting perspective i.e. assuming you dot/dab or baton plasterboard onto the PIR, if you wish to mount a heavy item on a wall do your screws have to be super long?

 

22 hours ago, Conor said:

 

9. Using ICF for internal walls eats up a huge amount of space (e.g. 280mm Vs 100mm) compared to single block or stud walls. And costs a lot more. Bit it is faster and DIY able.

 

Think I can get comfort at the space loss (as gain on other properties) but as you say, the trade off will be cost vs speed/DIYability

 

22 hours ago, Conor said:

 

One thing I would add, if you are doing this DIY, advise you to try and visit a build where it is happening. Also, you'll need to get your own structural warranty organised of not using a contractor. Factor in another £3k for that.

 

Current plan is to join a couple of courses from a short list of ICF manufacturers to see first hand the mechanics of the construction but you're right, nothing beats real world and I should try and visit a build where it's going up live. Re 3k structural warranty 1) ouch 2) thanks for flagging as had no idea. I've seen some people pay 10k to builders to put the ICF blocks together but if that is now a difference of 7k it maybe isn't such a no brainer to DIY it

[mjward]

19 hours ago, willbish said:

 

I sleeved MVHR prior to pour. Everything else has been drilled through after. If you can, design out waste pipes going through the exterior wall and send them all down through the slab.

 

good tip!

 

19 hours ago, willbish said:

 

Insulated raft for foundation, works really well with ICF

 

3/3... think the raft needs to be added to my notes

 

19 hours ago, willbish said:

 

Blocks arrived 26/03/19, first pour 29/04/19 to 2.8m. Just me. Also working day job 50% of the time. So 18 days for groundfloor 88m2.

 

that is seriously impressive. 

 

19 hours ago, willbish said:

 

 

 

Yes you've got it. Vertical rebar for any retaining walls

 

Potentially for UK too. I think it makes it more economical to buy a standard ICF product then add additional insulation. And cutting 200mm ICF blocks is a no fun.

 

From the U-values I saw from Isotex, you can get 0.15 with their 380mm block which is the one that appeals to me. That seems good enough for the UK

 

19 hours ago, willbish said:

 

Didnt even consider ICF for the internals, too costly, waste of insulation. I went with 100mm concrete block.

 

Do you have a ballpark what your sqm of concrete block came to? Did you build that yourself? The insulation angle I would like is more of an acoustic rather than thermal one so prepared to pay a premium for that, it just depends how much we are talking really.

 

19 hours ago, willbish said:

 

Yes pole plate with bolts cast into the concrete. If I was doing it again I think I would drill and resin. Fixing a pole plate to EPS and then pouring concrete behind resulted in a little more movement than I was happy with. Has been made good now but was a bit of effort.

 

Interesting to hear. I wonder if this is a poly vs woodcrete issue ie the poly doesn't hold it as well whereas perhaps woodcrete would? 

 

19 hours ago, willbish said:

 

 

 

[Pm1987]

1 hour ago, mjward said:

 

 

 

 

Did you baton all walls or just for services? Was wondering about thermal efficiency with the void vs dot and dab.

Used batons on all internal walls and plasterboarded over. 

1 hour ago, mjward said:

 

Thanks for this. Seems at the higher end of what I've seen but I will take from your pour figures that you are similar to me and would rather take a bit more time if it means getting it right!

This time scale was basically us just working weekends, nights and two weeks. Included in this time was erecting scaffolding, installing first floor posi and caber and waiting for the pump availability. You will find some people using the icf externally but blocking internally may give you a false sense of speed if you intent to use them internally. Please also do not underestimate the weight of the durisol blocks. They are easy to lift and fit at the lower levels but once you start on the second floor and gables (especially if they are wet) you will start to feel the pain.  Throw in some wind, rain and snow it get depressing pretty quickly. 

1 hour ago, mjward said:

 

 

Was wondering why your blocks looked so much bigger to what I had seen

The blocks we used are the D365 externally and D170 internally. I didn't feel the need to use the larger blocks internally and as someone else has stated they do take up a larger footprint.

1 hour ago, mjward said:

 

 

[Conor]

1 hour ago, mjward said:

How do this now look from a mounting perspective i.e. assuming you dot/dab or baton plasterboard onto the PIR, if you wish to mount a heavy item on a wall do your screws have to be super long?

 

 

Process is stick on the PIR with expanding foam, then baton out with 50mm batons (screwed through to webs), when first fixes are done, then screw plasterboard on to batons. Same for underside of roof joists in our vaulted parts. For fixing heavy items, we'll have about 175mm of "soft" stuff to get through to the core. But the batons will be able to take almost all mountings that you'd typically have... maybe not the likes of a wall hung toilet tho.

[mjward]

59 minutes ago, Pm1987 said:

Used batons on all internal walls and plasterboarded over. 

This time scale was basically us just working weekends, nights and two weeks. Included in this time was erecting scaffolding, installing first floor posi and caber and waiting for the pump availability. You will find some people using the icf externally but blocking internally may give you a false sense of speed if you intent to use them internally. Please also do not underestimate the weight of the durisol blocks. They are easy to lift and fit at the lower levels but once you start on the second floor and gables (especially if they are wet) you will start to feel the pain.  Throw in some wind, rain and snow it get depressing pretty quickly. 

The blocks we used are the D365 externally and D170 internally. I didn't feel the need to use the larger blocks internally and as someone else has stated they do take up a larger footprint.

 

 

Good to hear you went the posi route, only discovered it last week and seems a no brainer for the modern build and all the pipework/ducting it includes.

Hear you weight of the blocks, I lifted one up last week (yes just the one  ) and it's a completely different kettle of fish to the poly ICF. 

 

Thanks for you help, massively appreciated

[mjward]

56 minutes ago, Conor said:

 

Process is stick on the PIR with expanding foam, then baton out with 50mm batons (screwed through to webs), when first fixes are done, then screw plasterboard on to batons. Same for underside of roof joists in our vaulted parts. For fixing heavy items, we'll have about 175mm of "soft" stuff to get through to the core. But the batons will be able to take almost all mountings that you'd typically have... maybe not the likes of a wall hung toilet tho.

 

Ok, think I get it, batons can take TVs but for high kitchen cabinets and similar weight it would need reaching the core. What is your U-value with that added PIR?

[Conor]

2 hours ago, mjward said:

 

Ok, think I get it, batons can take TVs but for high kitchen cabinets and similar weight it would need reaching the core. What is your U-value with that added PIR?

 

40mm PIR on to the Amvic block brings it down to 0.16. plasterboard, render etc gives a finished wall of 0.15.

[willbish]

5 hours ago, mjward said:

From the U-values I saw from Isotex, you can get 0.15 with their 380mm block which is the one that appeals to me. That seems good enough for the UK

If your floor and roof have to be 0.11 to meet Part L having something similar for the walls is a realistic target to aim for. Unless you are building to sell like a developer, then just scraping through the current building regs seems a bit of a waste in my opinion.

 

5 hours ago, mjward said:

Do you have a ballpark what your sqm of concrete block came to? Did you build that yourself? The insulation angle I would like is more of an acoustic rather than thermal one so prepared to pay a premium for that, it just depends how much we are talking really.

I dont I'm afraid. I paid a brickie friend day rate to do the work and I laboured for him

 

5 hours ago, mjward said:

 

Interesting to hear. I wonder if this is a poly vs woodcrete issue ie the poly doesn't hold it as well whereas perhaps woodcrete would? 

Yes probably, I haven't built with woodcrete but its certainly got less 'squidge'!

[Nick Laslett]

What are people’s thoughts on UFH in insulated raft and the risk of the wall bracing screws piercing the UFH?
 

In an earlier thread it was speculated that you could mount the braces on scaffolding boards. 
 

Anyone actually used ICF wall braces on an insulated raft with UFH?

[mjward]

16 hours ago, Conor said:

 

40mm PIR on to the Amvic block brings it down to 0.16. plasterboard, render etc gives a finished wall of 0.15.

 

got it thanks

[mjward]

15 hours ago, willbish said:

If your floor and roof have to be 0.11 to meet Part L having something similar for the walls is a realistic target to aim for. Unless you are building to sell like a developer, then just scraping through the current building regs seems a bit of a waste in my opinion.

 

I dont I'm afraid. I paid a brickie friend day rate to do the work and I laboured for him

 

Yes probably, I haven't built with woodcrete but its certainly got less 'squidge'!

 

I will be the first to put my hand up to say at this stage I am not a U-value expert but I was under the impression the UK min requirements are significantly higher than 0.15 (off top of my head I think it's double that at 0.3) and that Passive Haus standard for walls is in the 0.1-0.15 range?

[ToughButterCup]

I have a moderate amount of experience with Durisol. Reading this will answer some of your questions.

Good luck with your project

Ian

 

PS: just a quick thought - order the right number Dursiol of blocks, and re-order a few weeks in advance if you think you might run short. Its not like popping down to the BM for another few blocks of whatever.

Edited October 23, 2020 by ToughButterCup

[Andy H]

On 21/10/2020 at 15:41, Conor said:

On 21/10/2020 at 15:41, Conor said:

We're adding an additional 50mm insulation to our standard Amvic blocks to get to u0.15 for passive House standards. It's far easier and cheaper to add PIR insulation to the inside of the walls rather than EPS to the outside. Can be done DIY over a weekend. Whereas external requires scaffolding, thicker sheets of EPS and lots and lots of big screws. You just need to factor in this loss of space in your design.

I can see the ease of adding insulation onto the inside of the building but the ICF suppliers seem to reduce the U value by increasing the thickness of the outside of the block. There presumably is a reason for doing this. Is anybody able to explain this?

 

[Conor]

Most structural attachments (e.g. steel beams, floor joists) to an ICF wall are from the inside, so it's better to have less soft stuff to cut way, minimising cold bridging.

[Andy H]

On 21/10/2020 at 18:41, willbish said:

Blocks arrived 26/03/19, first pour 29/04/19 to 2.8m. Just me. Also working day job 50% of the time. So 18 days for groundfloor 88m2.

That sounds like you were productive.

 

Which ICF supplier did you use?

 

Kind regards

 

Andy

[FM2015]

Andyh,

If you have a decent, thorough SAP assessor, he should be able to demonstrate how little actual realisable benefit you get from extra EPS on mass poured walls.  Wind chill is more significant for example.  That's why the general rule across all EPS products was, until more recently, 2-3".

 

A lot of EPS blocks have a fixing point which gets further away from the surface if you add EPS.  This can impact on any external fitments.  Extra EPS on the outside helps maintain steady core temperature but like I said, realisable benefit? To be convinced in a real world situation.

[Nick Laslett]

On 22/10/2020 at 21:42, Nick Laslett said:

What are people’s thoughts on UFH in insulated raft and the risk of the wall bracing screws piercing the UFH?
 

In an earlier thread it was speculated that you could mount the braces on scaffolding boards. 
 

Anyone actually used ICF wall braces on an insulated raft with UFH?

I have now passed this phase of my build, the ground floor walls pour has been completed. In the end the UFH pipes were cable tied to the top of the reinforcement mesh in the middle of the raft. The raft was 150mm thick, the top of the UFH pipe in most places was at 80mm, with 70mm of clearance from the top surface. In some areas where there was 50mm ducting for water pipe runs, the reinforcement mesh was lifted and the UFH pipes were at 110mm with only 40mm of clearance. 
 

The wall props were 114cm long, and placed 120cm apart with fixings at 18cm and 1m. For the front fixing the builder used M10x70mm tapcon style bolts, we had no UFH pipe where there were front bolts fixings. For the rear bolt fixings we used M8x50mm tapcons, there was UFH pipe present for all these fixings.

 

We ran an air pressure test during the prop fixing process and none of the UFH pipe work were compromised. The walls were poured with only one very minor incident and the props have now been taken down. Hopefully this helps anyone that is concerned with how ICF wall props work when you have an insulated raft with UFH.

 

 

[Nick Laslett]

On 21/10/2020 at 18:41, willbish said:

 

I sleeved MVHR prior to pour. Everything else has been drilled through after. If you can, design out waste pipes going through the exterior wall and send them all down through the slab.

 

My MVHR needs 200mm spiral ducting, I couldn’t figure out an appropriate sized sleeve option before pour day. So for the lack of alternatives, I put the actual ducting in place before the pour.