Bay window condensation/damp problem - solution?

Moved in to refurbished/replastered Victorian terraced home in mid 2013.

In the front lounge, north-facing bay window, there is damp or condensation. See diagram attached.
These walls are very cold. We don't see window condensation, but also don't much think there is water coming in (windows and base of wall were resealed, mid 2014). Window sill board has swelled a bit, however.

What is the solution?
We plan to carpet the room, which currently has bare floorboards. This may raise the temperature. Also, we will get better home heating thermostat control, as we yo-yo the radiator between on and off at the moment.

Mid 2014, during other work, a contractor filled some areas at the left, but these have partly degraded since.

Quotes we have received:

Quote 1:

Don't think we have the stomach to remove plaster all the way to top of wall - seems fairly radical and expensive, even though I understand why plasterboard would warm the room.

Quote 2:

More modest disruption and cost, but don't know if it will do the job. He spoke about getting a dehumidifier on timer during the winter.

Thanks for your advice.

 

water is getting in round the window. Look at the pattern under the windowboard. Redecoration will not cure it, nor will plasterboard, nor will damp paint.

Have a look at the outside.

 

Post pictures of the exterior.

Andy

 

Summer 2014, I had old flaking paint removed from all the white parts of the bay, repainted in an effort to seal. Windows were sealed in (although the sealant has degraded a little), and you see clear sealant at base of wall at floor.

The window you see is the main one that cops the rain and wind. It's not totally confined to the bay - there is some minor plaster degradation above the skirting on the side lounge wall behind the green porch tiles.

 

You have penetrating damp at the cill and at ground level. Your difficulties might be more extensive than you imagine.
As above, the proposals so far quoted are nonsense for whats needed.

I can take you thro what to do but only if you are willing to go all the way with answers to many questions and further pics? It can be tiresome but its your house - at a glance i've noticed 16 further points for your attention.

 

At a further glance at your earlier posts i now see that i gave you extensive advice on two or three past occasions in 2014 - on each occasion you disappeared without acknowledging or thanking me (or others)?

 

Happy to deal with questions, photos and acknowledgements.

 

oh boy. That sealant is something to behold. How do you think your exterior ground levels look?

 

What's wrong with it, bobby?

I don't know. What are you concerned about?
The concrete immediately in front of the bay cambers away toward the rest of the front.
The photo makes it look as if the surface is wet. It's not really; there has been no rain.
That said, I do seem some green. And I also now see some cracks in the cement surface. Maybe I should sort them out?

 

I reckon that rain will hit the bottom of the bay window, won't get absorbed by the bricks (as it's meant to do) as you've painted over them, run down the gap between the house and paving that you've tried to seal with silicone,
get trapped, can't evaporate and therefore penetrate into your house.

whole lot needs ripped up and dropped by 6 inches.

 

There's no point sealing and spraying waterproofing solutions to the outside - It won't work. First thing you have to do is rule out water ingress. I would hack off an area of plaster around the worse area - under the window sill - and look at the masonry beneath. Check to see if it is damp. If the weather stays dry you may not be able to tell. If so try wetting the outside with a hose pipe to see if the masonry changes colour. Once you absolutely rule out water ingress you can then decide what action to take.

 

It's interstitial condensation. Very common on bays.

 

Thanks for your replies, all.

 

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