wet under the floorboards

Hi,

I moved into my new home about 4 months ago. It is an upside down house (The garage and kitchen are on the top floor with the bathroom and bedrooms on the bottom floor)

After about a month I noticed green mould growing on the wardrobe and chest of drawers in the spare bedroom. The spare bedroom is below the garage and has 3 outside walls to it (1 to the side of the property and the other 2 are under ground).

I immediately bought a dehumidifier but it didnt seem to do much good and I quickly noticed a musty smell. I have been rubbing the furniture down with mould killer for the last few weeks and that seemed to be doing some good. However I noticed this weekend that one of the corners of the bedroom seemed damp so I moved out every dit of furniture that was up against a wall and everything was covered in mould (furniture, skirting board, walls, carpet etc).

I cleaned everything up and even pulled the wallpaper off to see if the mould was in the plaster (which it doesn't seem to be). I then decided to have a look under the floorboards. The floor is damp but not soaking wet but the walls are wet (especially the ones that are totally underground). I also noticed the floorboard that is directly under the damp corner is wet and the support beam is also wet. It is as if the wet walls have risen up to the beam and is starting to soak the beam and floorboard. The only other thing i noticed was the side of the floorboards that are facing the ground have a brown mould on them.

Can anyone tell me the way forward regarding the green mould and more importantly the damp?

Thanks for reading, apologies it was long winded but I wanted to get everything down.

tell us how the floor space and the spare room are ventilated.

Also tell us if you always use extractor fans in bathroom and kitchen,and if you ever drape wet washing about the house.

Is this a modern house that would have been designed and contructed to approved standards?

The spare room has an airbrick (all the ground floor rooms do). I do not know how the floor space is ventilated, I didn't see anything when I went under the floorboards. The only thing i noticed was a couple of bricks missing from the wall that was the most wet. The holes showed there was a gap and then another damp wall, I am guessing this was the cavity wall space.

There is no extractor fan in the bathroom just an air brick but there is one in the kitchen that we use if we are creating a lot of steam. We mostly dry our washing in the garage and sometimes put the odd sock, tshirt etc on the radiators but never in the room that has the problem.

The house was built around 1970 so fairly modern, the worrying thing is when we moved in there were no signs of mould or damp what-so-ever and the room doesn't look like it has been decorated recently so its not as if the people we bought the house off tried to hide anything.

I could go back under the floor and try to get some pictures if it helps.

the most common source of damp in a spare room is that it is not well ventilated, and is cooler than occupied rooms, so the warm moist air from the rest of the house circulates through it and causes condensation.

Damp under floors is usually caused by insufficient ventilation - there needs to be an air brick or two on each side so that the air can flow through it and carry away damp from the ground. Modern standards have a lot more air bricks than were used in the past.

If the previous occupants kept the window open more often, this would have kept the damp down.

However as you appear to have some underground walls (I am guessing house built into a hillside?) the walls and ground may be more prone to damp than usual, and this may vary with ground water due to rain.

Ventilation is always the cheapest and first thing to try when treating damp, but also look for the cause. A leaking pipe or drain will sometimes be the culprit, or gutter blocked and splashing down a wall. more often than not it is condensation, though. In most houses "rising damp" will not be the cause, although it is the most profitable area for damp-proofing companies to tell you.

Thanks for that, I will leave the door open and also leave a window open and see if that helps.

I have also moved all furniture away from outside walls.

The floor was damp but not wet so hopefully its not a burst pipe etc, next time it rains I will pop out and look to see if its overflowing anywhere.

As for ventilation under the floor, if nothing is in place how could I rectify that?

modern standard would be an airbrick every two metres or so all round the house under the floor, or at least on opposite sides. that way there will be airflow from one side to the other whenever there is a breeze.

You can also hire a 110mm core drill which cuts a neat round hole through brickwork. You can put a plastic liner (such as a cut length of soilpipe) in it to seal the wall cavity, and fit a plastic grille on the outside to keep mice out.

If you have a wall with no access to the outside air you may need to put a plastic duct in to allow airflow. Some photos and a floorplan will help work out how to do it.