Air bricks and condensation

[ox50]

We have stripped the floorboards in our living room - so back to bare floorboards.

Now the weather has started getting colder we have noticed that the floor and skirting boards in the two corners by the bay are wet to the touch.

We have a suspended timber floor so went underneath to check if there is any sign of damp. There don't seem to be any major issues with damp down there but I did notice that the air bricks are directly below where we are getting the wet floor and skirting board.

Do you think this could just be condensation forming at these points because of the cold air coming in? I've attached a picture of one of the air bricks (sorry about the poor quality - hard to get good photos crawling around under the floor!).

If it is just condensation forming where the warm air of the house is meeting a colder point, is there any solution to this? Would something like a telescopic vent mean that the cold air is vented to a lower point and stop this happening?

We are planning on insulating under the floor in the next few months, although the room does not seem to be much colder with floorboards and no carpet.

Thanks

 

[JohnD]

the airbrick would help dry out moisture. It looks like the end of that joist might be wet. Is there a radiator pipe near it? Or a dripping gutter, or a leaking wastepipe outside? Is there a puddle on the paving, or a raised ground level, above the DPC? Could heavy rain have been blown through the airbrick in a storm?

It looks like your house has a course of blue bricks as DPC, which suggests good-quality build. Are you near Staffs?

Condensation on floors is unusual because water vapour is lighter than air and tends to rise. Are there signs of water under the floor? Do you drape wet washing inside your home?

Have you got a puppy?

 

[^woody^]

Corners of rooms are prone to condensation issues as the weather changes. It will have nothing to do with the underfloor venting and location of air bricks.

LOL at blue bricks = near staffs. We use lorries to move stuff around these parts, perhaps others do too?

 

[JohnD]

very rare where I come from, except on Victorian railway buildings.

I have however lived in a place where the ends of red bricks are coated with white china clay and arranged in patterns. I don't remember seeing them round the midlands.

What I mean is, there are regional differences.

 

[ox50]

We in Oxford city centre - so not not too near Staffs! It's a pretty standard 1930s semi.

There is a small gutter leak on one side of the bay but we are getting this on both flat walls either side of the bay (if that makes sense) - not really in the corner. And it is only on the skirting board directly above the air brick. The rest of the skirting boards are dry including the ones in the bay, which made me wonder if it was something to do with the location.

Some of the joists are slightly wet at the ends in places but the walls feel pretty dry to the touch so I'm not sure where that water is coming from.

There aren't any noticeable reasons outside - the vents are flush with the ground so I guess there is the potential for water to be blown in but the ground has not risen above the DPC. And there don't seem to be any leaks anywhere from any radiators or anything. The ground under the floor was pretty dry considering how wet it has been recently.

And no - no puppies, or kittens, or children around (that I'm aware of!) to make the area wet.

 

[theprinceofdarkness]

What can I say, the ends of your joists are wet, so the clock is ticking for them. The cold draft from the air brick is blowing directly along the underneath of the floor boards, and I presume up through the cracks.
Job #1 is to sort out the joist ends, as you can't insulate under the floor with reducing the ventilation to the joists which will increase the rotting rate.
Job#2, once the joists have been sorted, some form of ducting should be used to drop the air entry level, tapering the foam could be enough.
Frank

 

[^woody^]

Job #1 and Job #2

It's only been like it since the house was built with no problems.

Why is it a problem now?

 

[JohnD]

It does look to me as if water is lying on those short blocks. I wonder if it blowing through the airbrick and lying on the ledge formed by the blue bricks. They are not absorbent so it would not soak in and disappear.

You say they are level with the ground so it could even run in, if puddles form outside. Is it paved or a flowerbed? Perhaps you could dig it out a bit. Has it always been that level? Surely your blue bricks should be above ground.