Underfloor heating and engineered wood

[Basil1974]

Apologies if this is not the right subforum

We are having an extension built and will be having an engineered wood flooring installed in it.

We are also having wet underfloor heating installed

The builder is going to put screed down and my question is how long do we need to wait after the screed has been poured to put the engineered wood flooring down?

Architect and builder giving conflicting answers

Thank you in advance for your help

 

[Onetap]

Ask the flooring manufacturers.

There is somewhere a code of practice for sheet flooring, that involved a humidity meter under a glass cover on the floor. The evaporating moisture had blown a sheet floor off, taking some of the screed with it.

 

[Agile]

It depends on the drying time! Its not so much time as water content!

With a typical 150 mm screed that could easily be 6-8 weeks but a lot quicker if the UFH is CAREFULLY used to speed drying but that has to be done from a VERY low start temp and increased only VERY slightly every day!

I can see that the builder will probably give a shorter time as he wants to get on with the job! The architect probably follows the flooring makers advice. Ask the flooring supplier for their advice!

The BBC placed a contract for a new floor in the BBC Club at Cardiff and the flooring contractor laid the floor without giving the wood enough time to stabilise its moisture content and it all buckled but that was not a UFH problem just how to lay the floor properly.

 

[Dan Robinson]

Out of interest, and as a laugh- what are the two sides offering you?

As a warning, a floor system we supplied - but didn't fit - has been laid and screeded since October.

It was turned on a couple of weeks ago, and after a while - the day the German floor layers rocked up to lay £20K's worth of engineered floor - a damp patch appeared.

Pressure tests and Thermal surveys later it was concluded the pipes were intact.

What had happened was the screed was a special {sic} Latex form and the upper surface had set trapping moisture between the DPC and top layer.

Eventually it broke out purely to scare the poop out of the builder.

 

[samtheplan]

Any floor especially wood should be laid on a traditional cement based screed with a relative humidity of 75% or less. This can often be achieved by simply leaving it at ambient conditions for 1 day /mm of screed. So if you have a 65mm traditional screed, 65 days should do it.

There are so slightly different rules for liquid screeds.

Additives such as flexidry can be used to "trap" the water and speed up the period however a safer option,but more expensive is to paint an epoxy dpm onto the screed. This will isolate the floor and adhesive from the "damp" screed.

 

[Onetap]

Additives such as flexidry can be used to "trap" the water and speed up the period however a safer option,but more expensive is to paint an epoxy dpm onto the screed. This will isolate the floor and adhesive from the "damp" screed.

If there's any significant amount of moisture left in the screed, the evaporating water vapour will lift any impervious membrane.

You cannot be certain how long the screed will take to dry out since it depends on thicknesses, temperatures and air flow through the room. The Rh meter, in contact with the floor under a transparent cover is the recommended way of ensuring the screed is sufficiently dry.

 

[Basil1974]

Out of interest, and as a laugh- what are the two sides offering

The architect pretty much 3 months for 75mm, the builder probably 3 days!!!