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how do you damp proof your loft space?

(14 Posts)
monairethu Sun 30-Sep-12 20:49:35

so you can put stuff up there without it getting mildewed?

lalalonglegs Sun 30-Sep-12 20:54:18

Why is your loft damp? Is it leaking? Is there condensation? Get to the root of the problem. Most lofts that are don't let in rain, shouldn't get damp because there should be ventilation gaps built into them so that there is plenty of air circulation.

discrete Sun 30-Sep-12 20:59:53

What lala said.

So long as there is ventilation and the roof is good, nothing should get mildewed.

monairethu Mon 01-Oct-12 09:59:53

thanks for your responses. the roof isn't leaking but there is condensation. we have problems with condensation throughout the house. i do try to ventilate as much as possible downstairs but how can you ventilate your loft? should i just get a builder in to have a look? or do i need a roof specialist?

FannyFifer Mon 01-Oct-12 10:01:28

There should be air vents in your loft, have never had a problem with damp in a loft unless I had a leak.

lalalonglegs Mon 01-Oct-12 10:42:19

Get a roofer in to create some vents. Make sure that the condensation isn't coming from some fixable problem first (my parents-in-law had really bad condensation in their loft because the flue from their bathroom extractor fan was damaged and venting into the roofspace...).

PigletJohn Mon 01-Oct-12 11:26:57


It is not very unusual to find a house with a modern felted roof that is dripping with water.

The two rarest causes are severe roof problems allowing rain to enter; and water tanks in the loft that should be cold, but due to a plumbing fault are warm and steaming.

The most common cause is excess humidity in the house below.

Water vapour is lighter than air and will rise up through a house until either it escapes, or it finds something to condense on.

The most common cause of excess humidity, condensation, damp and mould in UK homes is people draping wet washing around the home or hanging it on radiators. I may possibly have mentioned that before.

Another cause is hot steamy showers where an effective extractor fan is not used for long enough.

Water vapour will pass through ceilings, but is will be much worse if there are holes in the ceiling, for example where lamps poke through, or around pipes or ill-fitting loft hatches.

Also check that loft insulation has not been pushed right into the eaves to block ventilation. A loft should be cold, dry, and on windy days, breezy.

PigletJohn Mon 01-Oct-12 11:29:25


you say we have problems with condensation throughout the house so my guess is that the cause is not a faulty roof.

SoozleQ Mon 01-Oct-12 12:03:34

PigletJohn, I love your crusade against drying washing in the house smile

PigletJohn Mon 01-Oct-12 12:16:48

crusade against damp, mouldy houses sad

monairethu Tue 02-Oct-12 10:14:46

hi thanks for all your responses. our bathroom has no extractor fan at all and the one above the cooker in the kitchen doesn't work very well. if we got both of these sorted out do you think the loft would be dry or drier? this isn't a modern house - it's a Victorian terrace with double glazing that is at least 20 years old. quite a few of the windows have 'blown'. will faulty double glazing make a house damp too?

we do dry clothes inside but not on radiators. i can't really see what the alternative is especially in winter.

thanks in advance for any further tips you may have.

PigletJohn Tue 02-Oct-12 11:30:25

a bathroom extractor will help. Look particularly at the bathroom ceiling. Are there holes in it for pipes or for downlighters?

Victorian houses are naturally cold and draughty, with wooden window and open fireplaces. Modern double glazing cuts down the original ventilation a lot. The windows ought to have trickle vents, which you should leave open permanently. Mist inside the glazing units has no effect on damp in the house.

Have a look in the loft and see that the insulation is not flopped into the eaves and blocking ventilation. I presume the original roof has bee replaced and felt has been laid under the new tiles.

You can hire a Core Drill which will make a neat round hole in the bathroom wall for a duct to fit. Look for a Centrifugal fan which will be quiter and more powerful than an axial fan. At extra cost you can get a ducted fan that goes in the loft and will be about three times as powerful as a typical wall fan. Basic fans are usually rate at about a nominal 80 cu metres per hour. The wiring inside the bathroom should be done by a recommended electrician who is a member of a Competent Persons Scheme (ask him which one). Bathroom extractors are preferably wire to come on with the light switch and run on for 20 minutes or so, otherwise people who have an aversion to ventilation will not switch it on. It removes odours as well as steam.

Here are a few

halphgracie Fri 29-Jan-16 09:59:41

Let me try help I left a 1930s street house because I got scared about condensation issues would damage the property which I totally regret now as everything is fixable although probably very expensive in time and money. The issue with my previous property was that the house had been timber framed and plaster boarded by a house flipper, this had in effect created a air tight seal around most walls preventing it from breathing, there was water entering the foundations (which were full of rubble) and that water was settling in this rubble and then evaporating through the property taking a long time to actually evaporate as it had not where else to go apart from the air bricks at front and rear of property. Factor in an unvented back boiler which further put more moisture into the property, poor loft insulation and no tile vents along with down lighters without hoods in the bathroom which allowed steam to rise into the loft space...the result=

Terrible condensation on every window after rainfall even when no one would sleep in that particular room, Roof tiles dripping wet with moisture and dripping onto the insulation and items stored in loft, damaged lats and timbers and generally just a foisty smell.

The solution (although I couldn't do it at the time due to so much stress) would have been to clear out the entire foundations of rubble and add extra air bricks for ventilation, add additional vent to inside property to allow air flow, add air tile vents and ridge vents to allow cross flow ventilation to keep loft cold and dry, add 240mm loft insulation to loft for prevent heat escaping from rooms below and move well away from eves, add thermaline insulated board to landing to further reduce heat loss and water entering loft space, replace bathroom upvc cladding with aqua board and downlighters and sealed downlighters with airtight cover along with powerful extractor vent to stop vapour. Add addiitonal heat source i,e, stove and new combi boiler and radiators to keep property warmer and prevent condensation settling on colder surfaces.

Gutted I gave up on it, but it was a constant battle keeping on top of it but I wish I had tried now

sarahsarah76 Tue 15-Nov-16 13:18:51

sometimes its best to check online and see if theres any guides to it. central london lofts have a bunch of guides on their website i know that much

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