Recycled crushed concrete in place of MOT1 & floor build up

[Sunil237]

I am planning on digging out a 60m2 concrete floor, removing the current concrete floor and then building back up to do insulated UFH.

 

Currently the floor is a standard build from 1970s so a concrete base. My proposed build up is;

15mm LVT planks

70mm liquid screen with UFH

Laminon Underfloor Heating Grid

150mm PIR

100mm EPS

DPM

25mm sand

100mm concrete

150mm Crushed concrete or MOT type 1 compacted

 

Can I use Crushed concrete in MOT type 1's place? will a hire crusher work for this purpose?

 

Thanks

Edited May 10 by Sunil237

[LiamJones]

Yes, but it’s far harder to level and compact than type 1. I did the same, but if I did it again I’d get rid of the concrete or use it on the drive and get fresh type 1 for slab 

[LiamJones]

60m2 slab from the 70s is gunna be no thicker than 100mm. That’s 6m3 of concrete to crush. 12 ton maybe. £33ex a ton for type 1. £400. By the time you’ve hired a crusher, you’ll be no better off. £150 for a grab if you need to get rid of it. I’d just buy fresh type 1 in next time for sure

[JohnMo]

9 hours ago, Sunil237 said:

70mm liquid screen with UFH

Laminon Underfloor Heating Grid

150mm PIR

100mm EPS

Well done retrofit with decent amounts of insulation 😃 make sure the insulation is gap filled with expanding foam and all joints are taped.

 

Not really sure what the heating grid brings to the party though, I would delete it, replace with polythene sheet (separation between the aluminium foil and cement in the screed) then use staples to hold the UFH pipes in place.

[twice round the block]

It's cheaper to buy in agrigates as you need them, than to crush stuff yourself, and end up with a pile of excess that has been stockpiled and is always in the wrong place.

[JohnMo]

1 hour ago, twice round the block said:

It's cheaper to buy in agrigates as you need them, than to crush stuff yourself, and end up with a pile of excess that has been stockpiled and is always in the wrong place.

Buy by the lorry load is the cheapest and direct from the quarry, not the builders merchants.  Bags have a bagging fee in the cost, builders merchants just get from the local quarry and add profit and a bagging fee.

[Sunil237]

brilliant advice everyone! thanks for quickly reasoning me out of a potentially pointless approach.

Having re-thought it briefly my rear garden slopes downwards and it may be a perfect opportunity to make use of my excavated material and to raise it all to being level (with a fall).

 

@LiamJones Thank you for the calcs to give perspective. Any chance you can provide me a contact for grab hire? I expected to pay at the £300~ range.

@JohnMo the Laminon grid layer is something I had saw on Youtube and I liked it as it lays flat avoiding any voids, it's under £100 for the whole floor so not breaking the bank if it's a helpful product. I did have a google for a Polythene sheet but would this be a vapour control or DMP version?

Thank you for the tip on buying from a quarry, I have a few in a 15mile radius so will work with them  I would 100% get loose as I have the space for it

I really hope I can build up the floor in the way I plan.. It's going to be a big effort digging down 600mm!! a total volume of 39m3 

Edited May 11 by Sunil237

[JohnMo]

4 minutes ago, Sunil237 said:

Polythene sheet but would this be a vapour control or DMP version?

No it's definitely not a a DPM of vapour control. It keeps the screed from going under the insulation and stops hydrogen being produced by the contact of aluminium and cement, leading to lots of small holes in the surface of the screed. To save going so deep just dump the 100mm EPs and use 50mm of PIR instead. So you have 2x layers of 100mm PIR. Save you 3m3?

[Sunil237]

3 minutes ago, JohnMo said:

No it's definitely not a a DPM of vapour control. It keeps the screed from going under the insulation and stops hydrogen being produced by the contact of aluminium and cement, leading to lots of small holes in the surface of the screed. To save going so deep just dump the 100mm EPs and use 50mm of PIR instead. So you have 2x layers of 100mm PIR. Save you 3m3?

I read that people use EPS as a sacrificial layer and they expect it to be damaged. From my understanding the PIR would loose some efficiency if the foil were damaged. I will keep this in mind though as when it comes to actually do the work I may want to stop digging early or may get my levels wrong!