cold external wall advice

[handsomejackuk]

Hi, I have been living in my property for approx 20 years and we have a constant problem with the one bedroom having a lot of condensation and being cold has one radiator in it which i now think may be under sized, anyway the room is 4m by 3m with a ceiling height of 2.2m the longest wall is south facing, but get very little sunlight in the winter due to next doors house being much taller it is end of terrace stone construction. also has 3 other external walls all of stone construction, i have removed the plasterboards off this wall a few days ago as was getting very smelly and mouldy one of the boards was quite wet with what i think is condensation one piece of timber was rotten and very wet. all the other timber battens along the wall are all sound the wall behind is painted black with what looks like bitumen. this wall seems to be dry has been left to air for a few days and i see no water ingress. i was hoping to insualte this wall and need some ideas.. access to this bedroo m is quite awkward and 2400 x 1200 boards are to awkward to get in whole. i was thinking of 2400 x 1200 30mm insulated boards directly bonded to the wall these will have to be cut in half to get them n the room or to use 2400 x 1200 22 mm boards screwed to the battens, with some additional battens added for extra strength. is it advisable to fill the spaces between the battends with polystyrene panels or kingspan. my main concern is getting the cut boards to all fit nice and flush as i will be painting or papering and not plastering due to the mess and recent new carpet to bedroom.. my only other option is 1800 x 900 boards as these can probably put up whole, but i nthen need to add some insulation in between the battens...please advise

 

[foxhole]

You can check rad size here.
http://www.radcalcer.co.uk/

Room need ventilation to avoid mold and excess condensation.

You can get full size plasterboard sheets in by scoring thru the middle on grey side and folding the board in half [without tearing the paper on white side.] then when in room gently open up and screw to batons.Use tapered board and they can easily be taped and filled without the need for a skim.

 

[Deleted member 174758]

If the wall is black it is quite probably done with bitumen resin - not an uncommon "fix" in stone-faced Victorian properties in my vicinity. The main problem is that when the bitumen goes on you need to provide extra ventilation because the bitumen will trap any moisture already in the house (or exhaled by occupants of the room). Adding extra insulation may help, but only if you improve the ventilation

 

[handsomejackuk]

thanks for the replies... we normally try to sleep with the door open and do try to open windows as much as possible... as for extra ventilation what other things to consider please.. ?

walls are 24 inches thick so cant really put fans in and ceiling, there are some slotvents in the window these are normally kept open, i think we may have to look at upping the size of the radiator, and possibly move it to the main wall i don;t think where it is at the moment is a good position..

 

[foxhole]

Ventilation needs to be permanent, windows and doors can be closed.