dpm needed to lay vinyl on new screed?

DIY job so asking lots of questions!

Extension screed has just been done and is level with the subfloor in two knocked through rooms. Screeders said I could lay vinyl floor on it after about 5 weeks. It will be more like two months by the time I am ready to do it so should be okay.

One of the subfloors is floorboards so I need to cover that with ply/hardboard before the vinyl click floor. Problem is that this raises the level and as this is to be one continous floor between all three rooms then I will need to run the ply/hardboard across all, including the new screed.

Should I put a membrane on the screed first? Will standard ploythene on a roll do? I am assuming that there will be moisture in the screed for months (years?) to come.

(I'll be putting an underlay under the vinyl anyway, but it wont be nice if there is potentially soggy ply/hardboard underneath!).

 

Dont listen to your screeders advice.
You'll need the concrete area screeded level to your plyboards you are putting down on the timber section. Don't put any ply or hardboard over the screed!

You'll need to have a moisture test on your new concrete floor before you can determine the next step for the prep.

You'll hear it time and time again but let a professional do your prep at least.

 

Thanks for the info. Too late as the screed is at the level of the top of the floorboards. So, perhaps the only way to bring the screed area up to level is with additional underlay? We are only talking about 3 - 5 mm.

 

If it's at the same level as the floorboards then what is the issue?
Just underlay the lot and job done

 

Providing your screed is properly dried out that is.

 

Because I need to lay something solid over the floorboards before underlay don't I?

Screed drying times: seems to be a lot of conflicting info out there.But I was assured by the guys that they use quick drying screed additives, and everything I have read about that suggests 8 weeks should be ample (8cm thick), But I appreciate the only way to know for sure is to get a damp meter on it.

 

Standard sand & cement screed, dries at approx 1mm per day, depending on variables. Temperature, air flow and type of mix, being just a few.
If a screed such as A38 or Topcem was used, this can reduce the drying time, and with A38 this can be just one day.
The only way to tell properly, is to carry out a proper test.
I would guess, that a standard mix was used, as that would be cheapest, so could assume 1mm per day, but that`s why a test would be needed

 

I'll check back with them. I specifically asked for as quick a drying as possible. But who knows? It arrived on a ready mix truck (well, appeared to be two separate streams mixing at the nozzle). As far as I saw they just barrowed that in. I see from the finish that it has fibres in it but that's all I can tell.

 

What click are you going for?
Are your floorboards solid and level?

 

Sounds like a normal screed.
In about 28 days depending on conditions you could apply a liquid dpm. But as above you need a mositure test doing.

 

Not sure what click yet. Floorboards are pretty rubbish, the tongue and groove has come apart in places so there are wide cracks.

One solution would be to rip them up and OSB floor that room as that would be pretty much the same level across all three floors then. But ££...

 

Plywood the floorboards with 6mm ply, overlapping the joint between the original floorboards and the concrete floor by about 6", glue & either screw or nail it to the concrete ... then get a floorlayer to screed level with the ply.

I'd get a floor layer to do the whole job tbh.

 

And then if gluing to it a fibre screed over the lot.

 

Thanks guys. I would love to get a floorlayer to do the whole lot but with the missus already overspent on the flooring she wants money is a problem! It's a large area (38 m2) so the click and underlay is going to be approx £1,400.

I think I might go the route of replacing the floorboards with OSB as that is probably going to be my cheapest option to get a relatively good level all through. (That room is only about 10 m2 and I have to hack up sections anyway to run pipes and cables).

 

The Mrs always gets the blame!

 

In this case justified! I don't see the sense in spending £25k on a kitchen and then skimping on the floor by having me bodge it! But, apparently a five-burner hob and giant American fridge are more important....

 

Tell me about it

 

80mm you are talking circa 130 days drying time in ideal conditions, i would hazard a guess that you would be ok using a primer type dpm and then putting smoothing compound down to take out the level difference if you are plying out the floorboards

 

Adding a double layer of underlay isn't going to work so if the floorboards need plying then you have to add another layer of screed to bring it up (not sand and cement though)

First job is get a hygrometer on the new screed and see where you are at then damp proof accordingly then screed on top. Could be a sandwich system

 

Thanks mate. Taking out the difference from the ply height (say 3mm) with a smoothing compound: is that just creating a gentle slope where the two floors meet, or bringing the entire screed area up by 3mm?