DIY Doctor UK DIY Forums

Hello there.

We've recently converted a 19th century stonebuilt stable block into a residential dwelling. We moved in at the end of May and have been having constant problems with condensation on the windows and french doors.

The walls consist of a new skin of blockwork, 50mm insulation, cavity and the existing sandstone (tied to the new skin). A silicone membrane (aquaseal)has been sprayed onto the walls to provide additional waterproofing. Due to an unusually low pitch the roofs have 145mm of kingspan zero odp insulation, sarking board painted with bitumen, two layers of vent3 breather membrane and yorkshire stone slates.

The walls and ceiling have plasterboard (dot and dab to walls) with a plaster skim.

The windows are iroko hardwood with pilkington k double glazed units. There are no trickle vents but the windows can be left "ajar" for ventilation whilst in the locked position.

The house is heated via UFH (but this has hardly been required due to the level of insulation!).

My question is this: Should I be expecting problems with condensation to the extent that the windows and french door are literally soaing wet? I've spoken to the window bloke who said that the house is just drying out and that I should invest in a dehumidifier.

But will a dehumidifier work? Would it dry out the building too quickly and crack the plaster, if that is indeed the problem?

It is driving me crazy-mad to wake up to this problem every morning. I know it will be damaging the window frames and walls and probably causing mould formation (not good when you've got a 7 month old baby in the house too).

Any help or advice would be massively appreciated....

it may still be drying out, building do take a long time to dry.

I'm surprised that you've been allowed to use the "keeping the window ajar" nightlatch arrangement in liew of trickle vents as this is not allowed under the building regulations. (altho I do know of some building control surveyor who do wrongly allow this)

some other things that you can do to help are:-

don't dry washing inside
always ensure that you use the mechanical extractor fans in the bathrooms and kitchens.

A dehumidifier may help. The windows are acting as a dehumidifier at the moment. The relative humidity must be quite high for you to get that amount of water on double glazing. The drying out time should be quicker because of the dry lining rather than plastering.

Thanks for the advice to both of you.

I think we'll try the dehumidifier route. I must say I was surprised to see no trickle vents but we were told by our builder that they weren't necessary!

The condensation in the master bedroom is by far the worst - this is where the french door is located. I know that the combination of cold glass and warm air from deep nighttime breathing is causing the condensation but I'm reluctant to run a dehumidifier overnight for fear of waking up as dry as an old prune.

Is there anything else that could be contributing to the problem? Is the house "overinsulated" and not allowing water vapour to escape? Could we retrofit trickle vents and see a rapid improvement?

Even though we moved in in May, the windows were installed in January with the drylining and plastering done in March, so I would hope that the house would have all but dried out by now.

Thanks again.