Black Mould behind Kitchen Cupboards

Discussion in 'Builders' Talk' started by RAMX51, Jan 4, 2018.

  1. RAMX51

    RAMX51 New Member

    So, this kitchen of mine has been rather problematic.

    Information on Kitchen and house: built ~ 1900 terraced, kitchen extension installed ~ 1970, approximately 6m x 4m, 3 external and 1 internal walls, walls are ~1.5ft thick, solid concrete floor, 1 large window double glazed, 1 chimney breast and 2 alcoves all sealed up with bricks, outside walls are north south east, east wall is back onto a raised garden. ~1ft gap between garden and house but top is covered. whole kitchen is ~1ft above outside ground level bar the east wall.

    To begin with we ripped out the old 70's kitchen and when we did behind most of the cupboards was black mould. So we cleaned the mould away and let it dry thoroughly. Our initial thoughts was rising damp, but we dismissed this as there was no damage to any of the walls and no signs of cracks or tide marks. The only thing we could see was water marks where it seems water was running down the wall but not from any cracks or the ceiling.

    We had a company come in and the guy prodded his little tool in the wall took some readings, went outside and made some observations. He wanted to tank all the walls. We took his advice and moved on. Needless to say the price was astronomical. In the £4500 region. So we sought another opinion.

    We got another company in and they said that it was not rising or penetrating damp. They suggested thoroughly cleaning the walls and leaving to dry then applying a membrane to the wall, the plastic membrane, and then plaster boarding over the top. This was done. New kitchen installed. After 4 months, everything was good. No mould and no damp at all. I removed plinth and checked underneath.

    3 months later I noticed at the back of the house that there was a crack in the cladding caused by the stone garden wall collapsing and putting strain where it joined against the outside of the house. I removed the excess and repaired the hole. At the same time I noticed that there was a hole left in the wall going to the back of the units from where the original waste pipe was removed for the sink. I filled this as well.

    Now under a month later and there is black mould behind the units going up about 0.5ft. This is behind all the ground cupboards except the fan oven and its housing. Im guessing the ovens fans are producing ventilation as this wall was moulded previous to installation.

    Needless to say I have re opened the hole. I am wandering if this is indeed my theory that it is all caused by condensation or if it is rising damp. Also note there are signs of water running down the walls. Dehumidifier was reading ~80% humidity. Keeping it at about 50% now.

    Any advice would be great.
    Last edited: Jan 4, 2018
    Flame likes this.
  2. KIAB

    KIAB Well-Known Member

    Condensation,more ventilation needed, you got extractor fan over cooker?
  3. Ram, was any internal insulation added to that wall, or just plasterboard?

    A plastic membrane is only as good as it is unholy. I wonder if the fitting of the kitchen has peppered it with screw holes?

    It's hard to suggest what the cause of the current mould is, although it's unlikely to be rising damp due to having a membrane against the wall. It also sounds too consistent and even along that wall - except for the oven part, which I agree is likely down to that unit being ventilated.

    So suspicion, I think, must be of condensation on to what will be a pretty cold surface - solid walls, no insulation.

    Not sure what to suggest now - I guess you don't want to even temporarily remove the base units?
  4. KIAB

    KIAB Well-Known Member

    Cupboard wall, stone or brick.

    Don't like plastic membrane on a wall if stone, as it needs to breath, I would have built a stud wall, filled with insulation & covered with insulated foil back plasterboard, this would be you vapour check.
  5. RAMX51

    RAMX51 New Member

    I dont mind taking the units away, can always be put back together.

    The bottom units are freestanding and not screwed to the wall, only the top ones are.

    I have gone underneath the units and it is indeed condensation.

    Took a torch and could see the water beads reflecting in the light. Also found a bead of water in the corner of the room, the coldest part.

    Currently talking to our builder to get a 6 inch extractor fan to replace the 4 inch one and 3 vents on the external wall to add ventilation. Ordered some mould control products from america that should help aswell.

    Have removed the plinth for now and have a dehumidifier running and current extractor fan on most of the day.

    Will keep you all updated.
  6. RAMX51

    RAMX51 New Member

    Ok, so I have remedied it somewhat. Managed to get back there and clean all the mold away. Didnt take much, just a couple sprays and it wiped straight off with no stains. Which point me to think it is all condensation as damp from rising would make all the plaster and paint come off.

    I have however put a temp meter and hygrometer under the worktops close to wall where the space is and also got some just in the room for reference.

    Most of the time the rooms relatice Humidity is ~ 55% at 17-20 degrees C.

    Under the units however is another story. For some reason it is 82% relative humidity and 13 degrees C.

    On one of the nights just gone I could see my breath under there. It was like breathing in freezer air. And the 20 degrees above.

    Any ideas on how to stop this would be awesome, im guessing either more outside vents or forced ventilation by a fan.
  7. kiaora

    kiaora Well-Known Member

    The space behind the units has it’s own micro climate,

    It’s Mother Nature at work, moisture in the air condenses like rain does, when the air cools.

    To reduce the water in the air is the challenge, apart from warmer area, more ventilation,
    You need to consider how the water gets there,

    Cooking with no lids on the saucepans, drying clothes on radiators, no windows open,possibly a small leak ?

    Jord86 likes this.
  8. Mr Rusty

    Mr Rusty Well-Known Member

    Attached a vapour table. If you do the calcs you will see that 55% @ 17-20deg rises to 80+% @ 13 degrees. RH = actual water vapour/saturated water vapour at that temp. Inevitably for the air to be that much cooler, the actual surfaces must be much colder. 82% @ 13 degrees is going to condense on a surface less than about 8 degrees. RH is actually the ratio of vapour pressures, but you can see this correlates closely to the water vapour density in g/m3.

    The hole through to the outside was probably allowing cold, unsaturated air in behind, and if it wasn't condensing outside, it certainly wouldn't inside. i.e. the outside air is drier but colder.

    With condensation you can either reduce the water vapour in the air - use a dehumidifier, extract damp air with shower and hob extractors, don't dry clothes inside, or even draw in drier air to push out warm damp air (up your blocked in chimney for example). The problem with drawing in drier air from outside is it is usually cold!

    The alternative is to warm up the surfaces so the water vapour doesn't condense. This is the theory of internal insulation - the surface retains room temperature better as the heat cannot immediately sink into the cold wall. However, it is essential that the insulation is sealed in so that the room air cannot get behind it, or the room air will condense between the insulation and the wall - not good.

    Fact is, if you make water vapour through "living" it HAS to go somewhere. If you seal your room perfectly, it just builds up until it saturates and condenses. Control humidity with ventilation and avoid cold spots!

    This all goes to show that most "damp specialists" with their meters and membranes haven't got a scooby, or if they have they don't want to say "condensation" because it won't sell their remedies and treatments.

    In a house I'm working on, when we took it on the internal kitchen walls were showing really bad damp tide marks up the walls, and all the lime plaster was drenched. The house is currently unheated, the kitchen still has bare walls after we removed the plaster, and it is now 100% dry. You would expect if it was "rising damp" (which I am sure many people would immediately suggest) it would show up real bad in an unheated house. The fact it doesn't proves it was condensation - the old fella used to dry all his clothes in that room in front of the coal fire - guess where the water vapour went!

    Attached Files:

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