Raising the ground floor

[WWilts]

Small unheated extension, a kind of porch. Floor plan dimensions 1400x 3200 mm. Floor level to be raised from concrete sub base up to adjoining internal floor. Height difference 325mm

Intended: Click vinyl tiles atop 25mm levelling compound on second DPM & 100mm floor insulation. Beneath insulation, about 20mm sand blinding.

Q How to make up the remaining approx 175mm under the sand? Least costly option preferred.

[Annker]

How about making up the 175mm with further insulation?

I imagine you'd need to check if dimensional compression would be an issue at that thickness, but certainly would be cost effective labour wise. 

[Russell griffiths]

Is that a typo  or do you mean 25mm, where is the structural bit. 

If you put 25mm on top of insulation, then the first fat kid to fall over on it will see it cracking. 

 

[WWilts]

26 minutes ago, Annker said:

further insulation

Perhaps jablite 300mm

 

 

15 minutes ago, Russell griffiths said:

If you put 25mm on top of insulation, then the first fat kid to fall over on it will see it cracking.

Was thinking of levelling compound, the sort that allow 3mm thickness upwards. Unwise?

[saveasteading]

75 screed

150 pir

10 sand

90 hardcore or sub-base.

 

= 325

 

Porches are not warm places, and it will be unheated, so 150PIR is plenty, perhaps too much but allows if heating is added later.

So revised: 75/100/10/140

 

If diy and the screed is likely to be rough then reduce to 65 screed than 10 levelling compound.

[Russell griffiths]

17 hours ago, WWilts said:

Perhaps jablite 300mm

 

 

Was thinking of levelling compound, the sort that allow 3mm thickness upwards. Unwise?

But levelling compound is not structural, it sits on top of a concrete or screed slab to make it flatter. 

You cannot put it over insulation, it has no strength jump up and down on it and it will just break up. 

Needs 75mm of traditional screed or 50mm of liquid screed over insulation for the strength. 

[PeterW]

18 hours ago, WWilts said:

Small unheated extension, a kind of porch. Floor plan dimensions 1400x 3200 mm. Floor level to be raised from concrete sub base up to adjoining internal floor. Height difference 325mm

Intended: Click vinyl tiles atop 25mm levelling compound on second DPM & 100mm floor insulation. Beneath insulation, about 20mm sand blinding.

Q How to make up the remaining approx 175mm under the sand? Least costly option preferred.

25mm EPS, DPM, 200mm EPS, ~ 95mm concrete, topped with SLC.

 

 

[WWilts]

Minded to follow this general approach, using timber joists & 22mm T&G chipboard under click vinyl tiles:
https://www.kingspan.com/gb/en/knowledge-articles/a-guide-to-constructing-a-floating-floor/
But replacing PIR with Jabfloor EPS (3 x 100mm)

[Russell griffiths]

1 hour ago, WWilts said:

Minded to follow this general approach, using timber joists & 22mm T&G chipboard under click vinyl tiles:
https://www.kingspan.com/gb/en/knowledge-articles/a-guide-to-constructing-a-floating-floor/
But replacing PIR with Jabfloor EPS (3 x 100mm)

You don’t need 300mm if it’s an unheated space, and you don’t have ufh.