New Laminate Flooring - advice needed

[scotcruz]

Hi folks,

I have cleared the two downstairs bedrooms to put laminate flooring. Both bedrooms had carpets and I recently noticed muold on the carpet under the ottoman bed and condensation/damp on the lower parts of the bed. I have checked the under floor vents which are open and air is circulating adequately. I can also even feel the draught from some of the gaps so . I am assuming the cause is warm air (in the room) meeting a cold surface (floorboards) and causing sweating on the surfaces of the bed/carpet/underlay and eventually the floor??

Anyhow, when I lifted the carpet and the foam underlay the floorboards felt damp. The gap under the floorboards between the ground is about 15 inch or so with signs of water in the soil etc. (please tell me if I should be looking at something else)

I was planning to cover the gaps with clauk, put an aluminum air bubble membrane then fibre board before putting on the laminates.

I have been reading on various threads on the forum and the net advising not to put a DPM on floorboards so not sure if I am heading on the right path. Is my aluminim insulation a DPM?

Please can someone advise what would be the best course of action in my scenario?

thanks in advance

 

[JohnD]

Water vapour is lighter than air so it rises. Lift a few boards and find the source.

Common causes are leaking waterpipes, and rainwater entry from puddles on paving against the house.

 

[scotcruz]

Water vapour is lighter than air so it rises. Lift a few boards and find the source.

Common causes are leaking waterpipes, and rainwater entry from puddles on paving against the house.

Yes I will investigate when the rain stops. Both rooms have external walls so it could be the rain water. There is also a rain water pipe going in to the ground too which may be leaking underground..

Thinking what about the rain water from pavement/puddles.. what can I do.. lay pavements so water runs away from the property?

also once these issues are investigated am I safe to use the aluminium insulation over the floorboards?

 

[JohnD]

also once these issues are investigated am I safe to use the aluminium insulation over the floorboards?

No, but you can once they are fixed

 

[Doggit]

Are the air bricks under the floorboards clear.

Once the problem of the rising damp air is fixed, you should only need to put the fibre board down, and then the laminate.

 

[scotcruz]

Are the air bricks under the floorboards clear.

Once the problem of the rising damp air is fixed, you should only need to put the fibre board down, and then the laminate.

Yes the air bricks are clear and there is plenty draught/air circulation under the floorboards.

Will investigate further in the morning.. just wanted heads up and or any advice on what I should be looking at..

 

[Doggit]

Sorry for not reading your post properly Scot. Do you keep the windows open, and the room well ventilated, as excess moisture in the room would account for the problems you're getting.

 

[scotcruz]

Sorry for not reading your post properly Scot. Do you keep the windows open, and the room well ventilated, as excess moisture in the room would account for the problems you're getting.

I open the windows and have had the dehumidifier running on occasions with not much moisture captured in the bottle.

Theoretically I was thinking it was due to many gaps between the floor boards.. the cold air touching the warm carpet and turning into damp/vapor/moisture.

looks like the previous had lifted the floorboards to install the central heating and not done a good job of putting them back on.. there are so many gaps it's unbelievable and when you put your hand over the gaps it feels as though some has got a fan or aircon running.

 

[Doggit]

It looks as though you've got everything set up properly, so although you might have an issue with excess water getting under the floor, the only problem I can see in the room, is excess air gaps in the floorboards letting in more cold and moisture than they should. The big question becomes, if you cure any excess water in the soil under the floorboards, would you still have a problem with the airgaps. Normally, you'd put down hardboard to deal with any gaps in the floorboards, but as you're intending to put fibre boards down, this is tantamount to putting the hardboard to stop up the gaps, so in theory, you're on the right track.

Check out the excess moisture in the ground, and then get back to us.

 

[scotcruz]

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[scotcruz]

ok guys, so investigate earlier this afternoon. Glad to report the it was not what I suspected so that narrows it down to 2 options:

a) Warm air in the room meeting a cold surface (carpet/floor/ottoman bed/space behind cupboards) and causing moisture/damp/mould stains? The cold surface is because there are many gaps on the floor letting the cold air through.

b) Stale air in the room causing the moisture? There are Slotvents on the windows but no actual room vent? could that be the reason? I do open the windows often but feel the room isnt fresher. If so, what is the solution? Brick Vent or a 110mm round pipe vent?

Below are some of the photos I took:

1- Mould/salt stains on the wall behind the bed


2- Salt stains on the wall under the subfloor


3- Foundation and soil dry no water


4- Subfloor and joists from underneath


Btw the wall is an external wall, I have also checked the rainwater drain outside which is in good condition.

Based on the above, please advise what would be the best course of action before I lay the new flooring. Please tell me if I am overthinking, just dont want any surprises later on and want to understand why the carpet under ottoman bed had mould stains.

Appreciate your help and thanks in advance.

 

[Doggit]

If the brick vents under the floor are lined up correctly, then the airflow should take any moisture out of the under floor space, so I suspect you've got a combination of both a and b causing the mould problems. I don't think you need the dpm under the fibre boards, but hardboard down first to stop up the gaps, and then fibre board may be a good belt and braces solution.

 

[scotcruz]

If the brick vents under the floor are lined up correctly, then the airflow should take any moisture out of the under floor space, so I suspect you've got a combination of both a and b causing the mould problems. I don't think you need the dpm under the fibre boards, but hardboard down first to stop up the gaps, and then fibre board may be a good belt and braces solution.

Thanks mate.. that's very useful. only reason I wanted to put the aluminium foil insulation was to cover the gaps.

re: brick vents - can you further help explain the air bricks being lined?

I want to understand whether you should be able to see through the air brick vents. the one at the rear and front of the house I can see through..

The ones on the side wall which is external wall I didnt see one under the sub floor. I am assuming the vents on the side wall are for the cavity instead of the subfloor void?

is that right?

 

[Doggit]

The principle goes like this; don't bother covering the ground under the house, it'd be too expensive, but earth gets wet, and moist air under the floor will eventually start rotting the joists, and the floorboards. Air bricks get put in the walls to allow an airflow under the house, so keep taking rising moisture away from an enclosed space; so as long as the air bricks are clear, and either side of the house, then air goes in one side, and out the other. I've never come across an airbrick for a cavity, but it could be an early example of a weep hole.

I suspect that an air bubble membrane will collapse over time. If you're going to take that route, then I'd consider using an laminate combined dpm/underlay instead.

 

[scotcruz]

The principle goes like this; don't bother covering the ground under the house, it'd be too expensive, but earth gets wet, and moist air under the floor will eventually start rotting the joists, and the floorboards. Air bricks get put in the walls to allow an airflow under the house, so keep taking rising moisture away from an enclosed space; so as long as the air bricks are clear, and either side of the house, then air goes in one side, and out the other. I've never come across an airbrick for a cavity, but it could be an early example of a weep hole.

I suspect that an air bubble membrane will collapse over time. If you're going to take that route, then I'd consider using an laminate combined dpm/underlay instead.

super.. thanks for the advice mate..

only reason I assumed the air bricks on the side wall was to vent the wall cavity because I could not see through it when I was looking under the sub floor void.

I will install a brick vent to the front (under the bedroom window to ensure there is no stale air.

really appreciate it.. cheers