Damp bedroom help

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We were trying to make our bedroom better insulated, and hopefully less damp. I pulled the bed away from the wall and there's black damp up wall and all the staples in the headboard have rusted (id like to say from severe scuffing banging against the wall but no)

I am running a dehumidifier in the room and in the morning it's reading 80% dropping to about 50% after a few hours.

The house is an old L shaped bungalow this is the end room. There are no air bricks or vents in the room but has new double glazing throughout.

The current insulation is v poor disintegrated rockwool cross lined with 150mm topup rockwool.
I had planned to remove the old plasterboard (foam based sagging stuff) cut 100mm celotex into the joists and leave the cross lined topupup there. Any thoughts advice appreciated, my builder mate said be careful of cold spots doing this.

Ive noticed all the screws in the ceiling under the plasterboard have black spots too. Any advice on how i rid the room of damp. I think we had cavity wall insulation here as when i cut in the french doors in our bedroom the cavity wall had something like foam insulation but it was so weak and crumbly it fell apart as i touched it.

Thankyou in advance for any advice here. (i would pay people to do most of this but i am poor!)



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Ventilation and dehumidifier will certainly help. Cillit Bang black mould remover is great.

I had the same problems in a 1930s bungalow, still fixing now. Main problems:
  1. No insulation under floor - I've been putting insulation between joists (5cm kingpan with 5cm rockwool on top)
  2. No insulation on walls - I've put 5cm kingspan on wall, plasterboarded and skimmed (plasterer did the skimming)
  3. Sub-floor Air bricks blocked up - unblocked, added extra ones (1.79p each from Toolstation, but hard work breaking through 9inch of brick!)
This has made a massive difference, no more damp or mould.

On one side of the house the path had been raised too, partly covering airbricks completely and this brought water / damp into the sub floor. Loads of rubble on subfloor meant reduced airflow and moisture absorbed into an inch of dust too. So all subfloors cleaned out before insulating. Get a good dust mask and a lot of buckets! I might actually by an "ash vacuum" (seen some for about £30 on Amazon) when I do the last room and hall.

Lots of work, but mould is a killer - I was waking up at 2am unable to breath - literally standing outside in freezing temperatures gasping for breathe, thinking I was about to pass out.

You might need to replace floorboards and joists too. Joists are relatively cheap. If you open any floor up and work there, spray well with wood treatment (I used Everbuild triple action).

You could probably make some small changes, but risk is of damp coming back. Your problem sounds like condensation damp (often forms on cold walls behind furniture due to poor air circulation and ventilation) so insulation is the answer.


You'll also reduce your heating bills. We went from running the heating 24 hours a day in the winter to only running 3pm-10.30pm, then again 6am-8am. Insulation rocks.
 
Hello Jonbey thankyou so much for your time here. Just to add

Seen that Clit bang stuff yes but want to prevent it ever coming back.

A) All floors are solid screed flooring.
B) Walls seem to be dry lined hollow (there's a hollow knock on them like they are studwalls but it's all blockwork) but i guess dot n dabbed onto walls not sure. Going to cut out hole out shortly see what's behind but they feel cold like the airgap between wall and plasterboard is cold?

Interesting though about adding celotex backed plasterboard to walls, could be a plan here. cheers.
 
Ok I drilled a few holes as i was still convinced the boards have been applied to batons not dot n dab. I was right.

Now is this the reason or contribution to damp on walls the cold air behind this plaster board? Why use baton instead of dry wall adhesive? Just alternative method?

So I'm planning to remove all this.

Apply 50mm celotex to walls and then drywall it all.
How do I stick celotex to walls and then plasterboard to celotex thanks.

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if you are getting condensation mould then the old time method of dealing with it is trickle ventilation and constant trickle heat.
i cant grasp whats already been said but its possible that the cavity insulation is allowing penetrating damp through the inner skin (do you have rendering?) and your battening and boards have been done wrong.

see related threads at the bottom of this page and related pages, and use the search button for lots of better suggestions than i can give.
 
No render on external wall which is brick.

I intend to remove batening and boards and use this method instead



Do I need to add some sort of membrane to block vapour wick due to potential **** cavity wicking or not thanks.
 
find out if you have cavity insulation, and then call the xtratherm Mfr's for tech advice. show them whats existing and what you propose.
 
To insulate my house I used 50mm insulation backed plasterboard from British Gypsum. They were secured directly to the walls via dot and dab.
 
Sounds like what my rooms were like when I moved into my 1930s bungalow - they had battened plasterboard on walls, no insulation. Lots of condensation damp / black mould.

I recommended 50mm kingspan (or equivalent) + plasterboard, all stuck on with loads of everbuild pink grip foam - works a treat and easier to handle than insulation backed plasterboard, and you can seal all joins on insulation board before putting the plasterboard up.
 

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