Bay Window and damp internal sills

[LiMaS]

Hi there

Wonder if anyone can offer some guidance.

In the Summer I bought a 1930s flat in a small block (its first floor). The flat has an issue with damp, I think caused by condensation (apparently a known issue in this block - although not to me).

At the beginning of October, I started having an issue with mould in my spare room, my room and the living rooms, on external walls (and some cheap bookcases), but particularly under windows. I've dealt with this with better heating, ventilation and buying a dehumidifier. I wanted to resolve before I started decorating.

I've just started decorating - and this has revealed an issue with damp on the internal sills under the bay windows in my lounge, particular in the bottom corner of the windows. The property was rental and looks like the window sill was plastered over to conceal damp wood and heavily painted. I've attached some pictures. The putty being used as a sealant appears to be soaking wet...

We are at a loss as to where the damp is coming from - could this be a result of a long standing issue with condensation not dealt with or something more significant?

Any help/guidance/thoughts appreciated!

 

[foxhole]

Typical of heavy condensation.
Needs adequate ventilation to cure.
Extra heating will increase air capacity to hold moisture so is of no help.
Dehumidifier is very expensive way to remove moisture, ventilation is free.
Hope you don't dry washing indoors?
Kitchen and bathroom need mechanical ventilation.

 

[LiMaS]

Thanks.

The flat has been well ventilated since I realised there was an issue (as in windows slightly opened to avoid letting more moisture in, and doors open so air flows around flat) - but was getting very cold! Hence dehumidifier which was recommended for low energy use (but appreciate a lot more expensive long term than installing extraction fans - which I will look at when I start the bathroom) I read that heat would benefit as well if well ventilated - but thanks for pointer below.

Block of flats - so limited space for drying outside I would say 60 per cent outside 40 per cent inside (small items!)

Would it really cause damp to wood in corner though of sill though and not the whole of the wood? Do you reckon it could reflect a number of years of build up (it was a rental property for at least 9 years before I moved in, so may have been neglected!)?

Help much appreciated - new to all this!

 

[Flyboytim]

Windows, double glazed and uPVC not excepted, are subject to condensation because they are colder than the room air during the autumn, winter and spring months.

The condensate runs down and pools on the sill, eventually penetrating through pores and cracks into the reveals, the walls nearby and below, and any wooden sills etc.

In the case of uPVC frames there may be voids in the frame which are sealed with a silicone bead on the inner and outer junctions of frame with wall - effectively these voids are at similar temperatures to the outside air. Any internal plaster in contact with these cold spots may suffer interstitial condensation, and remain more or less permanently damp.

Ventilation may help remove some humid internal air or may make parts of the window frame colder and subject to even more condensation depending on wind temperature, direction and strength, and the effectiveness of draughtproofing in other areas of the house.

Humid areas of the house - bathrooms, kitchens etc., should have extractors, and doors should be shut to prevent this humidity spreading to habitable rooms. Bedrooms that have been in use should be ventilated for a short while in the mornings.

Forced air movement is effective in maintaining a negligible temperature difference between the air in the room and cold surfaces like walls and windows prone to condensation. Just like in your car, before the heating kicks in, the windscreen begins to clear when you put the blower on.

Just keep a flow of air towards the windows and areas of condensation dampness, using an ordinary desk fan, and the windows will cease to mist up after a while and the walls and sills will dry out. The later in the year you leave it the longer it will take to dry. Any areas to be repainted are best stripped, dried out then redecorated when fully dry.

A directed air flow will work out much cheaper, and more effective than a dehumidifier, which will work on air volume, not specifically on the damp surfaces. Since you are constantly breathing, cooking and otherwise evaporating moisture in the air, a dehumidifier is just working against you.

Blown air will get behind furniture and can be used to dry out closets etc.

As recommended above, increasing the heating will not help the problem, and neither will turning up the heat when the room is occupied and turning off the heat when you go out during the day or to bed. Try to maintain a lower temperature at all times with the system thermostat, just increasing temperatures to the minimum comfort between 18 and 21 deg if the weather gets colder.

 

[foxhole]

Drying any clothing indoors dramatically increases moisture content and with all other measures in place will negate them.