Roof leaks and problems with gutters can cause untold damage to the timbers of your roof so keeping water out is really important, however what about the water that collects in the roof due to condensation? Can that cause the same problems?
The answer is, like with so much about buildings, it depends on a lot of different factors.
To understand why it is important to think about how the condensation gets there in the first place.
As we live in buildings we produce moisture, it is almost impossible not to. Washing, cooking, even breathing all release moisture into the air. How much moisture the air can hold depends on how warm the air is. Warmer air holds more moisture than cold air. This means that when warm air cools down it has to release a certain amount of water. You see this a lot in bedrooms where the moisture released in to the air by people breathing in their sleep over night hits the cold glass of a window and it fogs up.
It is very much the same thing with condensation in loft. Warm air rises from the habitable rooms below, taking moisture with it. When it reaches the loft (which if well insulated should be nice and cold) the air cools and the moisture is released. Most of the moisture is going to collect on the coldest part of the roof which is usually the underside of the covering. This is also where the main timbers such as the rafters and purlins are held and that is why there is a potential for problems.
Timber is a really robust material, there are bits of wood still in use in buildings that have been around for hundreds of years. If they are well maintained and kept dry then there is no reason why they wont last for hundreds of years more. Problems happen with timber when it gets wet and stays wet. This can allow rot to develop and also assist the development of wood boring insect infestations.
So if the condensation is making the timber wet does that mean it is a problem and something needs to be done about it?
The answer is maybe!
Timber in a loft can be at risk from condensation but only if it is not allowed to dry out regularly and in many cases they may be just fine. Lofts are often quite drafty places, deliberately so as it is these drafts that help the timbers dry out. You will often see vents in the external wood at the edges of the roof or even vents in the roof pitches themselves. Even where these are not present you can get enough ventilation just through the tiles or through all the small gaps that will be there.
The timbers will normally also get a chance to dry out in summer, if you have ever been in a loft on a hot day you will know how warm it can get up there! All that heat really helps dry the timbers out and will stop them rotting.
Of course, that does not mean you don’t have to worry about the condensation completely. The drafts and summer heat COULD help dry it out enough but not always. It is possible that if the loft has been insulated in such as way as to block too much ventilation or if it has had something like spray foam insulation fitted then the condensation could just keep building up and creating the perfect conditions for rot and wood boring insects. You also need to be sure any water you see up in the loft has been caused by condensation and not by something like a roof leak or other problems.
So what do you do if you think condensation is causing a problem in your loft? The simple answer is to get a Surveyor to have a look.
The first thing they will do is check he moisture levels in the timbers and the relative humidity levels in the loft. After that they will check all the accessible timber for signs of rot or insects. They will then look at how much insulation is up there and see if it is blocking the ventilation. They may also check things in the rest of the house to see if excessive amounts of moisture are being created or not ventilated correctly. They will also carry out a thorough inspection of the roof covering to check for leaks, sometimes this may involve the use of a camera pole or even a drone.
The good news is, if you are buying a house and what to be sure there are no condensation problems in the loft (or any other nasties up there!) then you simple need to contact me to arranged a Home Buyers Survey or a Building Survey. Where is safe and possible to get in the loft I always go up there and my report will let you know exactly what is going on.
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