Uneven beam and block floor - DPM/Insulation/screed

[_Tiny_]

I'm about to lay DPM, 100mm insulation and 55mm of liquid screed, on top of my beam and block floor.

In some places, the beams are slightly taller than the blocks, by maybe up to 10mm. Note sure if the blocks were a bit under size, or the beams over size.

My concern, is that the insulation wont be fully supported and that the screed may later crack because the insulation can deform slightly between the beams where its supported.

Is this a common thing? Do I need to put down some sand or very weak screed to get an even amount of support everywhere under the DPM?

Thanks

 

[SpecialK]

Did you slurry over the blocks to fill all the gaps between them? If so I would think sand would be fine to fill the 10mm difference.

I used dry sand over my concrete floor to get rid of any dips. I was panicking about any slight movement of the PIR but the screed has gone down and its fine.

 

[steven williams]

Your blocks r probably flush with the beams on the end and then they are probably gradually getting lower than the beam the closer u get to the middle, is that what’s happening?

 

[^woody^]

Small indescrepences are OK.

That screed seems a little thin for that insulation, and may benefit from mesh reinforcement.

 

[SpecialK]

Should be OK with liquid screed? I have 55mm liquid screed and 100mm PIR..

Small indescrepences are OK.

That screed seems a little thin for that insulation, and may benefit from mesh reinforcement.

 

[^woody^]

I have 55mm liquid screed

10% thicker than the OP then .

Obviously it's down to the manufacturer's guidance, but liquid screed whilst potentially more rigid, will be less tolerant of movement as a de-bonded layer - and if this type of screed is going to fail, it tends to fail after a few years and a few cycles of seasonal movement and use.

A B&B floor will also have a certain amount of flex when walked on.

 

[SpecialK]

10% thicker? Both 55mm?

Fingers crossed it doesn't crack. Mine is over a concrete pad so hopefully less likely.

Would you recommend a thicker traditional screed?

10% thicker than the OP then .

Obviously it's down to the manufacturer's guidance, but liquid screed whilst potentially more rigid, will be less tolerant of movement as a de-bonded layer - and if this type of screed is going to fail, it tends to fail after a few years and a few cycles of seasonal movement and use.

A B&B floor will also have a certain amount of flex when walked on.

 

[^woody^]

10% thicker? Both 55mm?

Fingers crossed it doesn't crack. Mine is over a concrete pad so hopefully less likely.

Would you recommend a thicker traditional screed?

Apologies, I saw 50. I have similar problems with invoices sent to me.

I've always thought at least 65mm of screed when floating over insulation is about right