Latex fibre screed thickness over insulation (marmox-like) over concrete floor?

[js.b1]

Removing a hearth left a 22-28mm drop to the reinforced concrete raft (rest= of floor has asphalt on top).

Due to running low on Latex Fibre Screed I "padded" the area with 10mm Marm= ox-type bonded by Mapei Keraflex to the concrete (after cleaning & abrading= ). I left gaps around the cut down insulation so the screed could reach the= concrete. I know some people use holes on a 6" x 6" grid to help bonding/s= hear.

I was curious to see how strong it is... it seems ok.

Q - What IS the min Latex Fibre Screed thickness over "Marmox-type" insulat= ion that has been bonded to a floor?

I thought such screeds must be 55mm for domestic?

[harry]

st of floor has asphalt on top).

rmox-type bonded by Mapei Keraflex to the concrete (after cleaning & abradi= ng). I left gaps around the cut down insulation so the screed could reach t= he concrete. I know some people use holes on a 6" x 6" grid to help bonding= /shear.

ation that has been bonded to a floor?

I never heard of that make before. Are you an advertising troll?

[Tim Watts]

? Bit confused here...

What's a "latex fibre screed"?

Do you mean regular screed with microfibre additive and SBR admix?

Or is this a bespoke product?

I think I would have just infiled the area with ordinary screed to the finished level after coating liberally with a cement slurry if there was no asphalt on the raft.

However, as you have glued the marmox down, that would be fiddly!

So your screed will be about 12-18mm?

That would be fine for an SBR modified screed onto a solid surface, but not onto a flexible one.

However, you are adding fibres so that may make it more forgiving.

What is the final floor finish going to be?

Tricky - need more info...

[js.b1]

No harry, it was a typo:

Latex Self Levelling Compound.

There is a brand name, but I believe that is immaterial.

[js.b1]

That is what I expected.

The "test" was just a small 1.5ft^2 area which is not traffic'd.

I asked two online suppliers about the min thickness of screed / SLC over M= armox with underlay & carpet thrown on top. They said it was ok down to 12m= m which surprised me. I think they assumed the layer "behaved like a super = big tile" and Marmox had a 30 ton per square metre rating. That 30 ton rati= ng is distributed hence the restriction on min mosaic size.

Underlay & carpet.

I did not think SLC / screed had magically changed permitting such thin lay= ers. Hence my surprise at their suggestion.

[Tim Watts]

OK - for carpet - that could be easy to solve:

Can you find plywood in a suitable thickness to fill up the remaining gap?

Ply would spread point loads over the marmox and you could bond it down with a bit of flexible tile adhesive just to tweak the gaps and to ensure there is no "crunchiness" as the ply moves against the marmox.

[js.b1]

Hmm... might be simpler to throw very cheap tiles over the Marmox? Can not be worse than Asphalt or no-DPC quarry tiles and longer life than plywood. There is the cost of tile adhesive, grout of course, but should be ok.

One other supplier has said "8m SLC over marmox, then carpet underlay on top", so some suppliers are thinking == 8mm tile. That is not true re tile surface hardness, and tiles are set usually on a flexible adhesive, with grout.

[Tim Watts]

Yep - tiles will work.

I have tiled over marmox and no problems at all[1].

[1] But for high load aread like the loo base or where the bath feet would go, I followed Marmox Technical's advice and left a cutout in the marmox and filled it with SBR modified screed so that the load was taken direct screed- concrete and not through the marmox.

Unless anyone is going to put a piano or a washing machine on the affected area, I think you will be pretty safe.

Cheers,

Tim