What on earth?

I have pulled up a laminate floor in our living room and found a bit of a surprise.

The floor was floating on quickstep DPM foam underlay on top of wood fibre carpet underlay.

Under that, 2/3 of the floor was marley tiles bonded with bitumen to what appears to be council concrete paving slabs! No DPM was present here, but it appears as though the bitumen glue was preventing moisture ingress to a limited extent. This had cracked due to settlement of the slabs so there was a little moisture coming up allowing the wood fibre underlay to rot in a spot near the centre of the room.

The house is 200 years old and the internal walls have been moved a bit over this time, so the other 1/3 of the floor is a concrete slab with DPM.

The floor has about 2 inches of runout across its length and the slabs have settled to different heights.

The fireplace hearth is also a mess - concrete surrounded with a bit of screed.

The walls have no DPC so the exposed bricks under the patio door were allowing moisture ingress. Surprisingly this is the only area where the laminate flooring was slightly swollen/damaged


My two questions here are:

1. Have any of you ever seen such a subfloor in the past?
2. Is there anything that could be done to make it useable/float a new laminate or engineered wood floor over the top without adding significant thickness?

 

Think that would need digging up. but you could go with
Ardex NA
Ardex DPM1c epoxy moisture suppressant
Dpm underlay up wall a inch
Laminate

 

It might be worth seeing if it can be asphalted,would probably cost around £25sqm and would be done and useable in a day

 

Thanks for the advice Daz, the Ardex NA looks like a good shout.

Because of the relative heights of the big concrete slab and floors in adjacent rooms, i think i would need to try to remove the undulations from the floor to make it flat but not perfectly level (about an inch lower at the front of the room than the rear). Would this be possible with the NA or will it just all flow to the lowest corner of the room at the front?

 

Thanks Paul. What thickness is asphalt generally laid to? I've seen a lot of different numbers posted around.

 

I think it's usually around 20mm

 

NA. Isolator sheet and a floated floor would be my go to

 

Thanks for the reply Merit. Would it have to be a vented isolator such as fball stopgap or is that overkill for this application?

Would you suggest DPM1c and isolator sheet or could it just be done with isolator or DPM1c?

 

Ventilated would be good I think. If the floors really damp in a old house the surface dpm could push it up the walls. Ideally you need the floor to breath or you need to dig it all out and put a proper subfloor in with a mechanical dpm

 

Or ashpalt it

 

I have finally got round to dealing with this and plan to do the DPM sandwich system suggested above. There are 3 latex/epoxy systems that i can buy locally:

1. Ardex NA, DPM1c, NA
2. Instarmac Level it pro 30, DPM it, Level it pro 30
3. Mapei latexplan trade, mapeproof one coat, latexplan trade

I am leaning towards the mapei system because it is half the price vs the ardex & the datasheet says that latexplan trade is much stronger than both the ardex and instarmac systems.

Can latexplan trade be laid without primer to bitumen residues like ardex na? If a primer is needed, which one would work under the dpm sandwich?

I then plan to lay provent underlay and either laminate or engineered wood flooring (mdf backed rather than ply as i am wary of warping or cupping). Does that sound reasonable?

 

Switch out the latex plan trade for Mapie NA

 

Or use a watered down Mapie eco prim T primer if you already have the latex plan trade

 

Thanks Merit - i hadn't realised that Mapei NA didn't need primer.

I haven't bought it yet because I read the mapei epoxy dpm datasheet and it said it was unsuitable for floors without a mechanical dpm... so that is out.

I can get the tilemaster superflow 30 (cannot get pro flow locally, so will just have to be quick!) and plan to use it with the tilemaster epoxy dpm, which claims to work where there is no mechanical DPM.

I feel like i have gone round in circles a bit here, but would this system work? Superflow seems to be an Ardex/Mapei NA equivalent - is that correct?