advice for solid oak floor

[Largemoo]

Hi, I've recently had a solid oak floor laid to my living room (4m x 7m).
The oak was glued to level concrete after a parquet floor was lifted (which was stuck down with bitumen). A liquid DPM was applied before the new floor was laid.

The oak floor is 20mm thick 140mm wide and various lengths
It all looked wonderful at first and totally solid -I was very happy

Some 2 months on, most of the floor has come un-stuck and I'm bouncing all over the place. The floor has also expanded slightly, I'd say about 10cm all round.

The installers first told me it was high humidity, which I said was rubbish (after some discussion, they agreed), they then said I had a problem with damp. I responded by saying that they tested for this before installing (which was OK) and also laid a DPM.

They are coming round next week to start lifting the floor to see whats wrong

I suppose my question is - Is there anything else that could be wrong (my thoughts are incorrect glue used, not enough glue used, not letting the DPM dry before laying etc.) or has anyone else had a similar problem. I want to try and learn as much as possible before the discussions go any further?

Thanks

 

[WoodYouLike]

I suppose my question is - Is there anything else that could be wrong (my thoughts are incorrect glue used, not enough glue used, not letting the DPM dry before laying etc.) or has anyone else had a similar problem. I want to try and learn as much as possible before the discussions go any further?

Thanks

Not using enough or the wrong type of adhesive is most likely. If the underfloor had been too moist you would have noticed that 2 - 3 days straight after installation by buckling of the boards.

 

[Largemoo]

Thanks WoodYouLike,
the fitters returned and after testing with damp meters and finding no damp anywhere, they've decided to engage a specialist to seek out what has gone wrong. They're due to turn up in a few weeks time (which is a pain).
I suggested that they had hadn't used enough glue as that was my thought - obviously they dismissed the idea. They say they've used the same glue / floor combination loads of times without any problems.

still a mystery? when I have news I'll post it.
thanks

 

[Largemoo]

The expert arrived today and the findings are:

moisture in wood between 10% and 11%
the moisture content on the bottom of the boards are very slightly higher than the top - which I told is what you'd expect.
expansion of around 15mm across 1400mm span (room is 3.6m wide)
they took up some boards to have a look underneath and found that only 10% of the board was glued to the screed underneath

After the expert left (he will produce his report in a few days), the fitter took some damp readings of the screed underneath and said that it was high (some readings he took he said were off the scale). I then asked why these reading weren't there before the floor was laid and a week ago when he last tested - he said he didn't know. He now says that he doesn't think our concrete floor has a DPM which has caused the problem (although how he could have missed this in the first place is puzzling).

My view is that I don't think he used enough adhesive and probably didn't leave enough expansion gap round the edges?

Anybody have any views or comments - when the report comes through I'll post the results for anybody interested

Thanks

PS does anybody know how much expansion is normal over say a 1 metre width?

 

[WoodYouLike]

PS does anybody know how much expansion is normal over say a 1 metre width?

rule of thumb with solid Oak:
3mm per meter wide, minimum of 10mm, so yours should have been at least 11 - 12 mm all around

 

[WoodYouLike]

Should have been: your fitter should have left an expansion gap of at least 11 - 12mm.

 

[Roofer]

I obviously concede to WYL and other experts but would like to add my own (non professional) comments

Your floor consists of oak flooring glued to a liquid DPM applied to old bitumen adhesive on screed. You state that the expert says that 10% of the flooring is stuck to the screed, does he mean that?

Where is the failure? Is it between the oak and the glue or between the glue and the DPM or between the DPM and the old bitumen or between the old bitumen and the screed?

As I see it the glue is designed to accomodate the expansion and contraction of the flooring and is normally applied direct to the screed, in your scenario the glue has been applied to the DPM and you are reliant on the DPM having the same properties as the glue.

It's like wall tiles being adhered to emulsion, it doesn't matter how good the adhesive is you're relying on the emulsion sticking to the wall (which it doesn't)

Any help?

 

[Largemoo]

Thanks guys,

The board that we took up showed the following:
Adhesive covered 90% or the board (which in my mind is probably OK)
of that 90% I'd say only 10% had made contact with the concrete floor (this was apparent as the 10% had both DPM, bitumen and parts of screed attached to it). the failure was between bitumen and screed.
should all of the bitumen been removed?

so.....

If the oak should, under normal conditions, expand about 3mm per metre, the clearly some additional moisture/damp is getting in but what I don't understand is if a liquid DPM was used, where is the damp coming from? How good is this liquid DPM and if there is no DPM under the screed, is this the reason?

lots of questions I know....but intriguing?

 

[WoodYouLike]

Have you checked the air-humidity? Moist can come in through various ways, including high air-humidity etc

 

[WoodYouLike]

Thanks guys,

The board that we took up showed the following:
Adhesive covered 90% or the board

My partner just made a remark about this (and he's the floor fitter): did your fitters glue the boards instead of the underfloor? That would account for the 90% coverage, but wouldn't tell you how the bonding has been. I'm learning every day

 

[Largemoo]

Had a damp expert in today.
He says that a small amount of water vapour is rising through the concrete sub base and somehow getting through the DPC (assuming there is one). He says that its likely that this has been the case for some while but was probably evaporating through the cracks in the old parquet floor.
With the new floor, the liquid DPM painted on and the new oak floor have prevented the evaporation, effectively this vapour has slowly accumulated in the oak causing the problem.

This seems plausible to me - not sure what anyone else thinks?

My options are:
A) lay carpet
B) lift the oak, have the screed removed, have a proper DPC put in and re-screed and re-lay a new oak floor.

or C) - anyone have any idea's?

Thanks

 

[WoodYouLike]

I'm not a damp expert, but this sounds a bit odd to me.
Moist evaporating through cracks in the old parquet floor? Little damp problem going on for some time, but now appears because Liquid DPM doesn't seem to be working and moist has accumulated (over two months if I understand correctly before causing real problems)?
Also, not an expert on liquid DPM, never use the stuff so can't really comment on its effectiveness (if any), but the first part sounds really odd to me: the effect you are now seeing on the solid new floor would have shown on the parquet floor also, evaporating through gaps or not (which is IMHO the oddest bit). Did you smell 'damp' when the old floor was removed?

 

[Largemoo]

The logic, as explained to me, is as follows.
Moisture was seeping through the screed and as the parquet blocks had a considerable number of joints, seeping through the joints.
After the liquid dpc was laid, this moisture continued to seep through the screed but now hit the DPC where it started to accumulate. As the DPC is not 100% reliable, and because I doubt it was correctly done, the moisture found its way through and into the oak.

Seems logical to me if not a pain in the a**e, No one can find any other reason. I'm going to talk to my Buildings insurer tomorrow to see what they say - no doubt I'll be visited by another expert?

As a matter of interest, the floor has stopped swelling, I suspect due to the central heating being on and drying it out a bit. Most of the oak is not stuck down, when you tread in places you can hear it knock against the screed.

another funny thing with all this is that I can't find anyone that has heard of this happening anywhere else? seems odd?

Thanks again for your help WYL

 

[flooringman]

I would agree with WYL on most of the points she has mentioned and I use liquid dpm quite a lot as I do stick down solid wood floors.(Don't lets not get into that argument again WYL eh!).

Usually I use products either from Sika or F.Ball - both are excellent and both do one and two application types. You do need to follow the instructions and if the job has been done with a two application product using only one application then problems can occur.

I have not known of problems with these products and if you know the manufacturer of the liquid dpm used I am sure they will be willing to help as most have a technical services deparertment.

 

[Largemoo]

Thanks Flooringman.
They used a sika liquid dpc, single application, which they say they have used many times before without a problem.
There was no smell of damp when the parquet was pulled up.
I do now begin to wonder whether they should have removed the bitumen before using the sika? As roofer mentioned earlier, the weak link is between the bitumen and screed.

My House insurers are now sending someone round to have a look.