Underfloor heating and Engineered wood floor problem

[andymach23]

Hi Matty

The installer did not add a vapour barrier. Just the underlay.

If there was an effective vapour barrier and the screed had a high moisture reading, would the screed eventually dry out and where would the moisture escape to?

When screed is drying, I take it then that the surface will be significantly drier and may mislead that the screed is dry enough?
Have you any experience of screed drying times with UFH switched on? Does this lessen the 1mm per day?

The damp meter I'm using isn't very sophisticated. Just the el cheapo Draper 2 pronged effort which I find useful for an ameteur poke around It gives the high pitched constant tone on the dark brown bits of flooring. It gives no tone at all on the adjacent boards that appear normal.

I think you may well be right about the moisture getting up between the underlay sheets. I can't figure though why the same screed in the old rooms of the house is not showing the same issue. These boards are 100% so far. As said, the only real difference here is the UFH plastic strips are orientated perpendicular to the planks.

Cheers, Andy

 

[mattysupra]

moister and how quick effect the flooring along with different heat etc can make a big difference.

Also was all the concrete bases and screeds the same thickness? One section open more to rain etc ? Without seeing the job and doing some tests at the moment this is all guess work.


The moister meter your using is no good for anything either really. it will tell you that water is wet and thats about it.

Screed drying times (+ you have the concrete base under the top screed) is normally around 1mm per day on adverage.

You can get faster drying and slower drying concrete/screed. As for running the heating it will normally help to dry the floor but then things like the humidity in the area can also make a big difference. Like i say tho , 1mm per day is the adverage.

When the concrete has had about 1mm per day to dry you should then take moister tests with a hygrometer. This device will tell you if you concrete/screed is dry enough to proced with fitting or if you need anoth month or even longer before the moister content is sutible to install on.

it could be that the underfloor heating is drawing the salts etc out of the concrete that are being forced into the timber and affecting the natural tanning of the wood?

There are a few things that can be the cause of your problem. Without myself or another independant inspector coming out to undertake tests on your floor we are guessing.

 

[mointainwalker]

@mattysupra

When you say it's 1 day per mm drying time, what percentagehumidity or relative humidity are you saying is achieved or should be achieved ?

 

[mattysupra]

@mattysupra

When you say it's 1 day per mm drying time, what percentagehumidity or relative humidity are you saying is achieved or should be achieved ?

1mm per day is an adverage time.

different concrete/screeds etc can be faster or slower drying.

also different thickness can play a big difference.

If left to dry at 1mm per day you should end up with a "expected" date that the subfloor will be ready for moister testing. Not installing.

This should in theroy leave you a subfloor below 75%rh. The room/air humidity is going to be different every day as it dries. The 1mm per day theroy is for a heated room with an adverage 50-65% humidity.


P.s, if the subfloor is over 40mm deep it can jump down to approx 1/2mm per day (standard site mix)

 

[rache_anders]

Hi @andymach23 - did you ever discover what it was? We have found the exact same issue in our new extension and trying to figure out what the cause could be....many thanks in advance!

 

[gsf600y]

Interesting read. We're looking at an extension with UFH.
Sounds to me like the golden rule is to be totally sure of the moisture levels before thinking about laying flooring.

Also interested to know if dehumidifiers should or shouldn't be used to help aid removing moisture. Can they help extract moisture from the screed?

EDIT: I suppose another question I have is, how long do you wait before installing furniture into the room?
We're planning UFH in the kitchen and lounge, and would want to get the kitchen installed well before the moisture levels are down, and ditto putting furniture into the lounge.
Furniture with flat surfaces particularly might slow down the escape of moisture surely, and you wouldn't want to install flooring until the entire surface is moisture free I guess? I suppose you could temporarily elevate some furniture onto feet to get some air flow underneath.

 

[crazydaze]

Installing the kitchen and putting furniture in the area is fine, it's residual moisture that needs to escape and this will occur naturally, forcing it out with a de-humidifier will have some effect but will not drastically shorten drying times.

It's imperitive to ensure moisture levels are correct before installing the Wood Flooring, it doesnt matter if the flooring is being glued to the subfloor or floated on an underlay, the concrete needs to be dry, you also have to ensure the heating is off a few days before installation and that when re-commisoned, the correct increase in temperature is adhered to.

To speed installation times you can look at installing a Liquid DPM that will allow you to install more quickly but look at the specs of the Liquid DPM before commiting.