TF wall / floor detail.

[Jason L]

Morning,

what do you think to my wall / floor junction ?  its a timber frame with K-render on a carrier board on the outside and internally it has 25mm pir insulation, services void and plaster board.

 

I have shown the beam and block floor on a DPc, bit is this even needed anymore, is it a old detail carried over from when timber floors were used ?

 

Below the DPC on the outside i have the render carrier board and dark grey K-render to cover the Thermoblock and blockwork ( have been told its ok to use below the DPC )  ..... has anyone got any other ideas for a sheet material to use to face it below the DPC ?

Thanks

[Moonshine]

How are you going to get ventilation to the floor void, i would show the proposed routing of your telescopic vent.

 

What U-value does those walls give you? it seems a bit on the light side.

[Jason L]

58 minutes ago, Moonshine said:

How are you going to get ventilation to the floor void, i would show the proposed routing of your telescopic vent.

 

What U-value does those walls give you? it seems a bit on the light side.

here is the air brick detail,   the SAP guy worked the walls out to 0.13 u-value.

[Moonshine]

13 minutes ago, Jason L said:

the SAP guy worked the walls out to 0.13 u-value

 

I not sure if that is correct, my quick calc indicates its more like 0.20, assuming 15% bridging by softwood in the mineral wool and the air cavity service void. I am not sure how they came to 0.13! 

 

 

 

[Jason L]

1 minute ago, Moonshine said:

 

I not sure if that is correct, my quick calc indicates its more like 0.20, assuming 15% bridging by softwood in the mineral wool and the air cavity service void. I am not sure how they came to 0.13! 

 

 

 

cheers,  i probably should have said, its 140mm of Recitcel Eurothane GP between the studs and 25mm of it on the inside

[Moonshine]

3 minutes ago, Jason L said:

cheers,  i probably should have said, its 140mm of Recitcel Eurothane GP between the studs and 25mm of it on the inside

 

?use the same hatching for it

 

[Russell griffiths]

Why have you got your airbricks underground, it’s not really a good idea and can lead to problems. 

[Jason L]

21 minutes ago, Moonshine said:

 

?use the same hatching for it

 

sorry, the proper insulation hatch doesnt work very well for the 25mm thk pir when plotted at a smaller scale

[Jason L]

21 minutes ago, Russell griffiths said:

Why have you got your airbricks underground, it’s not really a good idea and can lead to problems. 

i cant see any other way tbh,  what problems can it lead to ?

[tonyshouse]

Periscope vents, and you don’t need lintel over an air brick 

[Russell griffiths]

14 minutes ago, Jason L said:

i cant see any other way tbh,  what problems can it lead to ?

You use a telescopic vent to bring the air back up to your damp course level. 

 

Problems, the trench you have made around the building can collect with debris leading to water ingress through the vents. 

Poor air flow due to vent hidden under ground. 

 

Do you have to have beam and block its a poor floor construction insulation wise. 

[Mr Punter]

Any chance of passive slab / raft type foundation?

[Jason L]

30 minutes ago, Russell griffiths said:

You use a telescopic vent to bring the air back up to your damp course level. 

 

Problems, the trench you have made around the building can collect with debris leading to water ingress through the vents. 

Poor air flow due to vent hidden under ground. 

 

Do you have to have beam and block its a poor floor construction insulation wise. 

ahh it never really crossed my mind to not have beam and block, maybe a traditional concrete slab, maybe easier, it will certainly overcome the under floor ventilation thing!

[Jason L]

23 minutes ago, Mr Punter said:

Any chance of passive slab / raft type foundation?

i will have a look a concrete slab or raft solution instead, i have not had any dealings with a passive slab before, is that something that has to be designed and laid by specialists ?

[Mr Punter]

There are quite a few on here that have done passive slab.  It has insulation with reinforced concrete on top, thicker around the edges.  It does need specialist design.  They often have underfloor heating pipes run through the slab.  @PeterStarck has one.

[Gone West]

Yes I have a passive slab and the insulation is by Isoquick. Ours was the first Isoquick installation in England and we had the Isoquick insulation laid for us but having seen it installed it could be done DIY as it just slots together like a jigsaw puzzle. If self leveling concrete is used it would be relatively straightforward. We did encounter some problems which are in our blog.

 

[Bitpipe]

1 hour ago, Jason L said:

i will have a look a concrete slab or raft solution instead, i have not had any dealings with a passive slab before, is that something that has to be designed and laid by specialists ?

 

The principal is straightforward - pre-formed high density (200 or 250 grade) EPS is used to form the slab perimeter and sheets used for the underside. Sits on a blinded, free draining stone base. Membrane over the top of the EPS.

 

Reinforcement is then laid on chairs on the EPS base and UFH pipes are clipped directly to this. Services laid and then concrete poured (sometimes power floated) and you then have a slab with integral UFH that is fully insulated off the ground and to the sides. Savings on traditional shuttering for the slab and slab build up (e.g. xps & screed) offset the cost of the special EPS.

 

The whole system needs to be designed for your ground conditions and structure above.

 

The insulated layer of the slab is intended to line up with the insulated layer of the structure above so you end up with a complete insulated envelope around the structure.

 

I did something similar when building my basement - laid 300MM EPS 200 to support the slab which was cast on top using traditional shuttering, as were the basement walls. I ensured the under-slab EPS extended at least 200mm beyond the concrete and stuck 200mm sheets of EPS 70 to the external walls using LE foam. 

 

[Jason L]

1 hour ago, PeterStarck said:

Yes I have a passive slab and the insulation is by Isoquick. Ours was the first Isoquick installation in England and we had the Isoquick insulation laid for us but having seen it installed it could be done DIY as it just slots together like a jigsaw puzzle. If self leveling concrete is used it would be relatively straightforward. We did encounter some problems which are in our blog.

 

cheers  ?  yours was a bit of a nightmare, i bet that was a bit stressful.    im going to look at a traditional slab,  with the view to maybe adding a bit more insulation

[Jason L]

So i have redone the detail with a concrete slab, and it all looks much more sensible now, does away with the awkward air brick detail and  it should be quicker and easier to build thanks for the suggestion.

 

Any ideas for the facing of the exposed section of block / thermoblock, other than brick slips, its dark grey render at the moment.

[Mr Punter]

3 minutes ago, Jason L said:

Any ideas for the facing of the exposed section of block / thermoblock, other than brick slips, its dark grey render at the moment.

 

I have used some slate tiles in this situation.  They measured about 300mm long by 60mm high by 10mm thick.  Butted up with no grout.

[Thorfun]

On 01/02/2021 at 15:54, Bitpipe said:

I did something similar when building my basement - laid 300MM EPS 200 to support the slab which was cast on top using traditional shuttering, as were the basement walls. I ensured the under-slab EPS extended at least 200mm beyond the concrete and stuck 200mm sheets of EPS 70 to the external walls using LE foam. 

 

@Bitpipe I've got another question for you on this (sorry!). on your basement did you use a 'manufactured' solution, e.g. Kore/Isoquick/AFT etc for your insulated slab or was it just bought EPS and fitted together by yourselves/groundworkers? I know I've read all of your posts about your basement but this is one detail I can't remember you mentioning.

[Bitpipe]

1 hour ago, Thorfun said:

 

@Bitpipe I've got another question for you on this (sorry!). on your basement did you use a 'manufactured' solution, e.g. Kore/Isoquick/AFT etc for your insulated slab or was it just bought EPS and fitted together by yourselves/groundworkers? I know I've read all of your posts about your basement but this is one detail I can't remember you mentioning.

 

Given we were using traditional timber and steel shuttering for the concrete works, we just used plain EPS 200 forms (300mmx1200mmx2400mm) for the slab and laid them on a 50mm blinded sand layer over 150mm compacted crush in a simple flat layer that covered the slab footprint with a 3-400mm overlap all round. I though they may need pinned but they are so heavy they stayed where they were placed.

 

The EPS slab was covered in membrane and the ground workers built their slab upon it as they normally would. When the vertical walls were cast, I simply glued (using LE foam) sheets of 200mm thick EPS 70 to their external face, sitting them on the EPS 300 that projected from under the slab. This completed the EPS envelope that rose to meet the MBC frame. MBC provided a steel and timber web as the ground floor into which we laid UFH spreader plates & pipes and decked over with 22mm OSB. The build progressed as usual from there.

 

My understanding is that Kore and the like are used when the EPS is the shuttering for the concrete.

[Thorfun]

2 minutes ago, Bitpipe said:

 

Given we were using traditional timber and steel shuttering for the concrete works, we just used plain EPS 200 forms (300mmx1200mmx2400mm) for the slab and laid them on a 50mm blinded sand layer over 150mm compacted crush in a simple flat layer that covered the slab footprint with a 3-400mm overlap all round. I though they may need pinned but they are so heavy they stayed where they were placed.

 

The EPS slab was covered in membrane and the ground workers built their slab upon it as they normally would. When the vertical walls were cast, I simply glued (using LE foam) sheets of 200mm thick EPS 70 to their external face, sitting them on the EPS 300 that projected from under the slab. This completed the EPS envelope that rose to meet the MBC frame. MBC provided a steel and timber web as the ground floor into which we laid UFH spreader plates & pipes and decked over with 22mm OSB. The build progressed as usual from there.

 

My understanding is that Kore and the like are used when the EPS is the shuttering for the concrete.

thanks, that makes sense. I ask because I have a quote from a groundworks company that is just using Stylite EPS and building the slab and walls like yours so it's good to know that it worked for you! I've got no issues with it as EPS is EPS as long as they're ok with it and it all connects well I see no benefit in paying extra for an 'engineered' EPS solution.

[Bitpipe]

8 minutes ago, Thorfun said:

thanks, that makes sense. I ask because I have a quote from a groundworks company that is just using Stylite EPS and building the slab and walls like yours so it's good to know that it worked for you! I've got no issues with it as EPS is EPS as long as they're ok with it and it all connects well I see no benefit in paying extra for an 'engineered' EPS solution.

 

As long as it's just bearing a flat load and is not expected to contain concrete then you are fine.

 

Get your SE to spec the lowest strength EPS you need for the slab based on N/M2. EPS200 was good enough for us - it gets progressively more expensive for 250 and 300 grade. If you can, avoid cutting the slab EPS it as it is very dense - a hot wire or small chainsaw are effective means - the latter does generate a lot of EPS chaff!

 

Walls don't need to be more than EPS 70 but again get the SE to confirm. Easy to fix these to smooth concrete, simply wet both surfaces with a hose and apply a generous bead of Soudal LE foam (with a gun) and slap them together. You may need to prop the vertical slabs until they adhere, takes 15 mins or so. Then squirt any gaps between sheets. Our SE advised putting sheets of 2-3mm corex over the EPS to protect when back filling. It's very cheap. I tried stapling it but reverted to using old nails salvaged on site to peg it in place! 

[Thorfun]

5 minutes ago, Bitpipe said:

Get your SE to spec the lowest strength EPS you need for the slab based on N/M2. EPS200 was good enough for us - it gets progressively more expensive for 250 and 300 grade.

sadly we need EPS300, specified by Tanners.

 

6 minutes ago, Bitpipe said:

Walls don't need to be more than EPS 70 but again get the SE to confirm. Easy to fix these to smooth concrete, simply wet both surfaces with a hose and apply a generous bead of Soudal LE foam (with a gun) and slap them together. You may need to prop the vertical slabs until they adhere, takes 15 mins or so. Then squirt any gaps between sheets. Our SE advised putting sheets of 2-3mm corex over the EPS to protect when back filling. It's very cheap. I tried stapling it but reverted to using old nails salvaged on site to peg it in place! 

thanks for the tip.