what underlay over 2 different subfloors?

24 Jun 2004
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United Kingdom
We just had 2 rooms knocked through to make a kitchen dinner.

We want to lay a single wooden floor throughout to make it a more consistent space, i don't want a tiled floor and I understand engineered wood is best in a kitchen area if we go for wood.

My problem is working out what underlay to use, as one part of the room has floorboards over a void, while the other is a new concrete floor.

Can I use a single underlay throughout or do i need 2 different underlays for each section?

Also do I need a damp proof membrane?
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Hey spxy,

First of all yes i would advise that you go for a high quality engineered wood flooring as its much less prone to movement. Also as its going into a kitchen dinner, where there is likely to be some red wine spilt over the years, I would advise that you treat the floor with an additional treatment to protect your flooring.

Treatex is a popular choice and makes the floor nice and easy to maintain.

Is there underfloor heating in the new concrete floor? If not then Elastilon Basic can be used throughout. Alternatively Elastilon strong can be used on the underfloor heated concrete and Elastilon Basic can go across the existing floorboards. Elastilon is a high quality self adhesive underlay and we have found it to be very popular. Rather than me going into loads of detail I would advise that you take a look at the Elastilon Demonstration Video on the following page.


Also yes it is good working practise to put down a DPM before the underlay on the screen but not on the floorboards.

Hope this helps.
NEVER use a DPM over existing floorboards, this can cause condensation and eventually rotting joists.

You have to try to create one type of underfloor, installing hardboard or plywood sheets (diagonal) over both floors (nailing/staple over floorboards, gluing down in concrete), then - if installing the floor floating - use an underlayment that does not contain a dpm.
thanks for the replies, will take it on board.

Maybe boarding over is an option but how will that effect the different humidity ventilation issues in each subfloor?

Is there any reason not to use two different overlays for the the individual sub floors and then lay the flooring over?
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No there is not. The great thing about an underlay such as Elastilon is that it can be used on a number of different surfaces.

Is there under floor heating on the new concrete floor? If not then i cant see any reason why you cant use the same underlay for both.


hi JFJ, thanks for the reply

no there isn't any underfloor heating.
Personally then I would use a DPM over the new concrete and then use Ealstilon Basic throughout. This is perfectly adequete, easy and cost effective :)
Except when there is residue moist in the concrete. The DPM over the concrete will be able to stop this entering the wood there, but not where there is no DPM over the existing floorboards.

Overboarding, where you use flexible adhesive to glue down the hardboard or plywood onto the concrete will prevent residue moist getting anywhere.

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