Laminate flooring and damp issues

[bdh198]

I have recently bought a ground floor flat that appears to have a damp problem (I knew there was a damp issue prior to purchase and managed to negotiate a discount).

I've had a damp surveyor look at it and on initial inspection it appeared to be rising damp, but on closer inspection it seems that it could actually be the laminate flooring that is causing the damp problem. The flat is a 1950s build two bedroom ground floor flat, there is no evidence that either the damp proof course in the walls has failed or that the damp proof membrane under concrete floor has failed.

The damp surveyor has identified the laminate flooring as a possible cause. The underlay of the laminate flooring includes a thin plastic sheet that covers the concrete floor right up to the skirting. The damp is all in the lower part of the walls (the first couple of feet) and is particularly bad in the skirting boards (some of which have completely rotted).

The surveyor believes the air under this plastic sheet is condensing and the resulting moisture has nowhere to go except to the edge of the plastic sheet, where it meets the skirting. It is then seeping into the skirting and into the walls.

My question is, how should laminate floor be properly laid over a concrete floor to protect the laminate from this kind of moisture, but to avoid simply transferring the problem to the skirting and the walls?

We are thinking about replacing the laminate (that looks like it has been done cheaply - the previous owner was a buy-to-let landlord) with carpet. Should we avoid using any water resistant underlay to allow the air to circulate and avoid trapping moisture?

Any thoughts or suggestions greatly appreciated.

 

[dazlight]

I tend to put a liquid DPM done on the concrete then the underlay then laminate

 

[ree]

As above in a typical situation without the kind of damp conditions described by the OP.


OP, There appears to be some confusion in your post over what kind of damp you are referring to?

If you remove a skirting from the wall you can check for a DPM thats been lapped up the wall behind the skirting, and if the plaster has been run down to make contact with the concrete?

The moist air under the underlay that the "surveyor" claims to have spotted must have come from somewhere? But i dont think that is the issue.

Here's what you could do:
Remove the rotted skirting, and lift the laminate & underlay in that area and post pics on here.

There's possibly more to the damp issues in the whoile flat than mentioned so far but, for now, stick with the wall/floor/skirting issue.

 

[Hyper88]

The only way you will find out what is going it is to try to carefully remove one of the laminates.

I have a gut feeling you have water trapped from a either water leak either past or present. The plastic is trapping the water. The source of the water may even be a water leak from a flat above. Water may have fallen a couple of years ago, but the water will still be trapped. There is no way for dry up.

 

[bdh198]

This first picture shows what was immediately below the laminate floor. This underlay is only 2mm thick.

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• bdh198
• 29 Mar 2015
• 1

This second picture shows the plastic sheet underneath that first layer of underlay.

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• bdh198
• 29 Mar 2015
• 1

This third picture shows the floor underneath both those layers. This isn't the concrete and appears to be something 'painted?' onto the floor. It's a black tar like substance about 2mm thick.

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• bdh198
• 29 Mar 2015
• 1

This forth picture shows a lot of water staining on that flooring. There is no obvious indication that this has come from a leak.

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• bdh198
• 29 Mar 2015
• 1

However, this final picture shows an area of the floor where some of that black tar like substance has come lose. There was moisture under that damp proof layer.

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• bdh198
• 29 Mar 2015
• 1

This picture helps to show what that black tar like substance looks like.

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• bdh198
• 29 Mar 2015
• 1

Firstly, is this the correct way to install laminate flooring? With a very thin underlay and a plastic sheet?

And secondly does anyone have any thoughts as to whether this moisture could be coming from condensation from the way the laminate has been laid?

 

[bdh198]

After digging around a bit it seems there is a concrete sub floor with about a cm of screed on top which is then covered with the black tar like substance. It looks like the black tar like substance might have been applied twice because there seems to be patches of moisture that is causing a layer of the black tar like substance to come away from a much thinner layer of the same black tar like substance which covers the screed.

 

[ree]

My earlier suggestion was to remove a length of rotted skirting and pic & post the wall and floor?

From the above pics the bitumen was most likely a liquid bitumen thats been painted on.

 

[Hyper88]

"Firstly, is this the correct way to install laminate flooring? With a very thin underlay and a plastic sheet?"

If the floor is level you can get away with a 'thin' underlay. The plastic sheet is not common, although have seen in used in 1980s Barratts developments.

It is unclear why they put bitumen (I am not sure if this is normal for a 1950s house) or perhaps they were trying to resolve some problems.

I have noted in the photos. The thin underlay is 'dirtier' on the underside then on the top.

There is also a 'whiteness' which I am not sure what that is. However, London does have limescale, so it could be residue.

Do you live at the bottom of a hill?

It is worth talking to your neighbours on the ground floor, just in case they have similar issue.

 

[bdh198]

Thank you for the replies.

The flat is near to the bottom of a hill. There is a stream at the bottom of the hill (presumably the lowest point) and the flat is about 20-30 meters from that. However, there is no high ground directly outside the property and the damp surveyor mentioned that provided the DPM under the concrete was not compromised then there shouldn't be any rising damp from ground water.

The flat is also in London and there is a high lime scale content in the water.

It is correct that the underlay is dirtier on the underside than the top (that's the side that's in contact with the plastic sheet).

I will pull away some of the skirting and show that when I visit the flat after work this afternoon.

In the meantime here is one further picture that shows patches of mould in between the plastic sheet and the underlay.

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• bdh198
• 31 Mar 2015
• 1

 

[Hyper88]

There are a number of theories in my head :-

1. Water from occupants - e.g. spilt a bucket of water. if this had happened, then the water would have not way of drying off, especially if trapped between plastic......

2. Water from underground streams

3. Rain Water water flood - I remember going to a viewing a flat about 10 years year ago and the house was at the bottom of a hill. The street gutters could not cope with with so much rain and that house was flooded out.

4. Leaky pipe - Check they have not burried pipe work in concrete.

5. Check for leaky pipes from bathroom. Run the bathroom and check under the bath panel. Check failure of sealants around the bathtubs. Especially if bathroom if adjoining to the problem room. Though suspect your expert may have checked for this.

 

[bdh198]

Now that the skirting boards have been taken up there seems to be a gap between the edge of the floor (screed and the bitumen solution) and the wall in which the skirting board sits. Presumably if the bitumen solution does not go all the way to the wall and the wooden skirting board does not sit on top of it any moisture under the bitumen solution layer would simply soak up through the skirting board.

The wooden skirting boards, especially the bottom edge , were very damp, and all the nails securing them in place were extremely rusty.

Gap between upper part of the floor and the wall in which the skirting board sat:

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• bdh198
• 5 Apr 2015
• 1

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• bdh198
• 5 Apr 2015
• 1

This shows the rusty skirting board nails:

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• bdh198
• 5 Apr 2015
• 1

Is it sensible to recover the floor in a fresh coat of bitumen solution or similar damp proof layer, and ensure it covers the floor right up to the wall so that the skirting can sit on it?