bay window wall disaster

[shetlander]

I've just uncovered a nasty problem in my kid's room, and could use some advice on how to fix it up.
(1900-ish solid brick wall, not long moved in)
That room has been cold at the window side even with the heating at full blast. The carpet touching the wall of the bay window was wet and becoming stained, so I removed one of the thin hardboard panels below the window when I found it was wet too.

Behind was the remains of the original T&G that had been partially removed and smashed up, then just hidden behind these panels. The wetness was from condensation running down these panels; there is a gap between the brick wall and floorboards (suspended timber floor), and its right above a ventillation brick so its effectively outside temperature in there. Worse, the wall behind all this timber is covered in what looks like an original layer of mortar but was also damp to the touch and had been falling away.
I've stripped out all the T&G and cleared up all the fallen mortar, and am letting the brick wall dry. The surrounding walls to the window are the original lath and plaster.
I clearly need to stop this cold air/condensation but I'm wondering if its safe for the building to just seal up the gap between floorboards and wall. My neighbour says they just stuck foil backed insulation blocks to the brickwork under their windows and stuffed the gap with fiberglass insulation but should they have preserved the ventillation gap? Also, I don't know whether the mortar layer should be repaired to help preserve the wall's moisure balancing?
Hope you can help.. the rest of the family is staying with inlaws until this is fixed!!!

 

[^woody^]

Yes fill any gaps with expanding foam for larger gaps, or silicone seal or caulk. Or whatever really. It won't matter to the wall or floor.

Don't get hung up on wall moisture balancing.

 

[PTS2]

That room has been cold at the window side even with the heating at full blast.
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I clearly need to stop this cold air/condensation

Unless you insulate that wall it will always relatively cold. The hotter the air inside your house, the more water vapour it can carry, so perversely when it hits a cold spot more water can potentially condense out. So you need to reduce the amount of water in the air inside your house. Attempting to further seal one hundred year old houses is also problematic.

Common sources of large amounts of water vapour inside your house are bathrooms and kitchens, and hanging clothes out to dry on radiators. There are others - for example you exhale water vapour but you'll just have to live with that. Remove water vapour at source using extractor fans, and buy a condensing tumble drier.

 

[theprinceofdarkness]

I am intrigued by the edge of a board just on the side of the bay in the second picture. So is the whole outside wall lined with boarding? One would normally expect the brickwork from the bay to just run around the corner to become the "flat" front wall of the house. I wonder if it hides some major cracks?
I would let the brickwork dry out then fix on some foam backed plasterboard, and skim it.
Frank

 

[shetlander]

thanks everyone for the quick replies. In the bay walls I think I'll definitely fill the gaps and insulate with foam boards.

I am intrigued by the edge of a board just on the side of the bay in the second picture. So is the whole outside wall lined with boarding? One would normally expect the brickwork from the bay to just run around the corner to become the "flat" front wall of the house. I wonder if it hides some major cracks?
I would let the brickwork dry out then fix on some foam backed plasterboard, and skim it.
Frank

Here's a better view hopefully.. a closer look at that corner shown in previous image.

Except for the area removed (that was tongue & groove originally, then covered with the boards) all the remaining walls are original lathe& plaster, including the bay wall.(theres a wooden batten you can see running across just below the plasterwork, and above that its all lathe-plaster with an gap between the brickwork).
There has been some terrible bodgy plastering done at some point, so the corner of the wall (that used to be an original feature curved wooden post) is now buried in plaster and an anglebead.
The whole lathe-plaster wall along the 'front' of the house has another sizeable gap between floorboards and brick.. I'd imagine filling this in will greatly help warm that room, but I suspect the draught back there is what's keeping the plaster breathing and in good condition?
I'd like to make the room warmer but really don't want to be the guy some future owner is cursing when they find my repairs!

 

[shetlander]

Oh, and regarding the condensation.. thankyou! I can tell the wife that I was RIGHT to moan about all the washing on the radiators!