ICF and concrete ground floor slab with UFH and bracing

[Renegade105]

Hi Guys,

 

im new to the forum and hoping to begin our journey in January.

 

I am undecided on my ground floor slab. If we were to pour a concrete slab with Underfloor Heating pipes, we would polish it up after and use it as our flooring, hopefully saving some funds.

 

however, I’ve just been on an ICF site and realised the bracing for the walls really do need to be anchored into the floor.

 

how do I do that without piercing the UFH pipes?

 

Thank you very much all.

 

 

[Russell griffiths]

@willbish  did this. 

[Conor]

2 hours ago, Renegade105 said:

Hi Guys,

 

im new to the forum and hoping to begin our journey in January.

 

I am undecided on my ground floor slab. If we were to pour a concrete slab with Underfloor Heating pipes, we would polish it up after and use it as our flooring, hopefully saving some funds.

 

however, I’ve just been on an ICF site and realised the bracing for the walls really do need to be anchored into the floor.

 

how do I do that without piercing the UFH pipes?

 

Thank you very much all.

 

 

They brace from the outside. You'll need to have suitable ground for them to set the props in to. 

[willbish]

Depending what ICF blocks you are using, bracing from the inside is preferred.

 

I left the perimeter of the slab clear of UFH pipes. Then using coach screws fixed 5ft scaffold boards down. I could then fix the base plate of the prop to the scaff board.

 

It worked well, I've got straight walls.

Slight issue was when the wall needed trimming in, using the prop to pull rather than push, the scaff board lifted up. Stack of concrete blocks as a counter weight helped then.

[Nick Laslett]

7 hours ago, Renegade105 said:

Hi Guys,

 

im new to the forum and hoping to begin our journey in January.

 

I am undecided on my ground floor slab. If we were to pour a concrete slab with Underfloor Heating pipes, we would polish it up after and use it as our flooring, hopefully saving some funds.

 

however, I’ve just been on an ICF site and realised the bracing for the walls really do need to be anchored into the floor.

 

how do I do that without piercing the UFH pipes?

 

Thank you very much all.

 

 

I was worried about this. Someone suggested using scaffold boards under the bracing. 
 

I found these notes from ICFmag.com

 

https://www.icfmag.com/2009/06/bracing-101/

 

Quote

 

If a concrete slab has been poured, or if the floor contains hydronic heating coils, securing the footplate becomes more difficult. There are a few solutions:

Option 1: If feasible, brace from the outside of the structure.

Option 2: Fasten short lengths of 2×6 to the floor using a quality construction adhesive. Wait for the glue to cure, then screw each footplate to the corresponding length of 2×6.

Option 3: Fasten a length of 2×6 to the bottom of the strongback, then fasten the footplate onto the other end of the 2×6.

Option 4: One innovative contractor set a pallet full of water barrels on the floor, filled the barrels, and then fastened the footplate to the pallet.

 

 

For our insulated raft, the spec is for the UFH to be fastened to the eps, under the rebar mesh. The concrete is 150mm thick, that should give enough clearance for most fixings.

 

The topic of concrete fixings is a whole another subject. I did not find anything specific about what they use for the bracing, but these were all mentioned; Nailable Plugs, Atlas bolt, Tapcon screw, Thunderbolts, concrete screws, anchor bolts. 

 

Edited November 9, 2020 by Nick Laslett

[Conor]

30 minutes ago, Nick Laslett said:

 

For our insulated raft, the spec is for the UFH to be fastened to the eps, under the rebar mesh. The concrete is 150mm thick, that should give enough clearance for most fixings.

 

 

That doesn't sound right. You want the pipes tied to the top layer of mesh, so 30-40mm deep. At 150mm depth, the heat will never make it to the surface of the concrete.

 

Make sure you have the fact that the slab will be a finished floor. I.e. you'll need the concrete specced so it doesn't crack with the heating cycles, and is leveled to the right tolerances and power floated. 

 

Btw, you'll find that once you cost up all these difficulties and extras, a finished and polished  concrete  floor slab is no cheaper, if not more expensive, than a tiled or wooden floored screed. Factor in a min of £40m² for a basic polished concrete floor, on top of your normal costs.

 

And also weigh up other difficulties as the build goes on- how do you get electrics and water to your kitchen island? What happens to all the plaster and wet trade crap that falls on the floors? Others here have protected their slabs wil bots of carpet, plyboard etc. Not impossible, bit any savings may not be worth it or realised. But don't get me wrong, and insulated concrete raft is a great design.

 

[scottishjohn]

I would suggest youget a price for the concrete polishing first 

and then it all depends on what ICF system you use -woodcrete types do not need the serious bracing that poly types do -just plywood bracing attached in weakareas like corners and door =window holes

durisol +isotex+ velox ==check those out

[Nick Laslett]

7 hours ago, Conor said:

 

That doesn't sound right. You want the pipes tied to the top layer of mesh, so 30-40mm deep. At 150mm depth, the heat will never make it to the surface of the concrete.

 

Make sure you have the fact that the slab will be a finished floor. I.e. you'll need the concrete specced so it doesn't crack with the heating cycles, and is leveled to the right tolerances and power floated. 

 

Btw, you'll find that once you cost up all these difficulties and extras, a finished and polished  concrete  floor slab is no cheaper, if not more expensive, than a tiled or wooden floored screed. Factor in a min of £40m² for a basic polished concrete floor, on top of your normal costs.

 

And also weigh up other difficulties as the build goes on- how do you get electrics and water to your kitchen island? What happens to all the plaster and wet trade crap that falls on the floors? Others here have protected their slabs wil bots of carpet, plyboard etc. Not impossible, bit any savings may not be worth it or realised. But don't get me wrong, and insulated concrete raft is a great design.

 

Where will the heat go? Isn’t that the point of an insulated raft?
 

Why are my structural engineer drawings so explicit about where the UFH pipes should go?

 

I believe @IanR  has an AFT raft, and his UFH is clipped to the EPS, his concrete might only be 100mm. 

 

 

Edited November 9, 2020 by Nick Laslett

[Renegade105]

Thanks guys,

 

I was thinking of doing the polishing ourselves but now I am beginning to see that the complexities of doing it (once trades have left) plus the possibilities of cracks etc in the future has left me thinking I will just screed over  (With the UFH) once construction is done.

[Tom]

I've been pondering the same question recently. We are going to be using Nudura and want a powerfloated slab with UFH as the final floor finish on the largest section of our build. The problem as I see it with powerfloating is it needs to be done while the slab is still going off, so potentially we have our "final" floor finish essentially being used as a building site, which isn't ideal. With polishing at least you would be grinding off the top layer with all the fag butts and Ginsters crumbs... ?

I'm currently thinking we'll try to leave the floor to do as late as possible - at least until the walls are up (and the walls can then be braced against the oversite), then it can be protected to a certain extent with a temporary cover for first and second fix etc. 

[Bitpipe]

 

I recall from others here that power floating can be a bit stressful as it can only commence when the floor is starting to go off and if the concrete is late to site you can be doing this late in the evening much to the annoyance of neighbours etc.

 

Once set, concrete floors are also susceptible to staining from oils and other liquids, until sealed they are very absorbent. Then you have damage from drops, drags scuffs etc.

 

Corex is better than nothing but not very durable, you'd need to use ply or carpet to really protect it and that won't be cheap.

 

In a similar vein, we only installed our final staircase once the complete build was finished and all trades had left. We used cheap MDF stairs during the build and when the final stairs were ordered, we had all the final finished floor levels to measure from.

 

You can get a microscreed (2-3mm) that gives a polished concrete effect, we looked into this but went with resin instead.

 

 

[HerbJ]

7 minutes ago, Bitpipe said:

if the concrete is late to site you can be doing this late in the evening much to the annoyance of neighbours etc.

I remember it well.

Concrete delivery was late and weather conditions were such that concrete would not go off as quick as anticipated

Bottles of wine for neighbours, fish and chips for the MBC team.  2200hr in September, finally had to stop. 

[Bitpipe]

3 minutes ago, HerbJ said:

I remember it well.

Concrete delivery was late and weather conditions were such that concrete would not go off as quick as anticipated

Bottles of wine for neighbours, fish and chips for the MBC team.  2200hr in September, finally had to stop. 

 

Our 120m2 slab was in basement so never considered floating it but I remember our fifth and last concrete load arrived hours after the previous four - the pump needs to keep running (and they are noisy) so we didn't wrap up until 6.30pm.

[HerbJ]

Fortunately, the slab was only being floated to give  good surface for tiling and other floor finishes. So, the finish we managed to achieve was acceptable, though not to the expected standard.

 

It was never our plan to have a"polished floor" as the final finish.

Edited November 10, 2020 by HerbJ

[Mr Punter]

21 hours ago, Conor said:

Btw, you'll find that once you cost up all these difficulties and extras, a finished and polished  concrete  floor slab is no cheaper, if not more expensive, than a tiled or wooden floored screed. Factor in a min of £40m² for a basic polished concrete floor, on top of your normal costs.

 

The £40 in N. Ireland could easily be £100+ in SE England.

 

Resin works well as used by @Bitpipe and