Leveling above concrete

[sam]

I am in the process of removing our solid floors and our suspended floors to fit insulation and underfloor heating. 

 

Below our suspended floors the void is bigger than I had expected and below the void there is a concrete slab. I had originally expected to lay new concrete and PIR insulation. I am now considering using the existing concrete base and using EPS; aware that EPS is less insulative than PIR but putting more down to compensate.

 

The issue I have is the original concrete floor is sloping. At one end I have about 400mm to the floor level; 4 meters away its 300mm. I'm looking for suggestions to fill this. Would you just level with more concrete or is there something cleverer I could do?

 

[PeterW]

Just add more insulation in steps

 

EPS at 25mm sheets would mean you can step it down roughly (ie 25mm every metre) so it goes 200-225-250-275mm across the room.

 

Stick them together with low expanding foam.

[Russell griffiths]

As an alternative method

 

kango up the old concrete into tiny bits, leave in situ

add a layer of type 1 and whacker down firm 

blind with a thin layer of sand

damp proof membrane 

insulation

ufh

concrete topping with mesh. 

[Mr Punter]

I would use type 1 to part fill where it is over 50mm and sharp sand elsewhere, compact with a whacker to get it nice and level.  Cleaner and more forgiving than concrete and simple to DIY.

[sam]

Many thanks for the suggestions and sorry for the delayed reply.

 

On 09/07/2018 at 17:20, Russell griffiths said:

concrete topping with mesh. 

How thick do you think this would have to be? 

 

On 10/07/2018 at 08:54, Mr Punter said:

I would use type 1 to part fill where it is over 50mm and sharp sand elsewhere, compact with a whacker to get it nice and level. 

Would you think structural concrete above the insulation is required in this case, or would a liquid screed be sufficient?

 

[Mr Punter]

Either 75mm normal screed or 50mm liquid.  Double check with insulation and screed suppliers for peace of mind.  Put a thin strip of insulation around the perimeter.