Loft Condensation under felt

[theDIYkid]

Hi

I have a loft I use for loft space, boarded out...I've noticed the felt inside under the tiles can get damp, is this due to colder weather? more notice it on the nails that come thru from the tiles and felt where water droplets gather?

Any way to sort this? spray foam?

Thanks

 

[kbdiy]

Don't spray foam it whatever you do. You just need to ensure there is sufficient air flow through the loft to ventilate it. Is there space around the eaves such that air can flow in from outside and circulate through the loft?

 

[theDIYkid]

The eaves you mean the edges right? I havent added any thing to the edges and have lived there 10 years so it should be, how can I check? its really cold up there...do the eaves join onto the skirting along the house?

Tiles go right down to the eaves/edges where ducting joins for waste, do I need to check I can get thru to the loft from there for the air flow?

Thanks

 

[tony1851]

As kbdiy, spray-foaming is the kiss-of-death to a roof - don't even think about going there.

Plenty of roof ventilation helps - check that any insulation quilt isn't rammed down tight into the eaves (the part at the low edge of the roof).

Clearly, some moisture vapour from the rooms below is getting into the roof - do you have a bathroom fan? and hopefully you don't dry clothes on radiators?

 

[KenGMac]

sz1, hi

What is happening is that, water vapour, from cooking, drying clothes, showers, baths is migrating through the plasterboard and the Insulation into the loft space.

What then happens is that because the warmth can not get into the loft, but water vapour can condensation WILL occur, the heat within the rooms in the house cannot get into the loft space because of the insulation. Water vapour is a molecule air temperature is simply a change in the background, ambient heat in the air.

If the roof void, the loft space is not adequately ventilated then the dampness that has percolated into the loft space simply has to condense on any cold surface.

You would not believe what happens if there is no or limited ventilation a loft space when the Home owner has increased the depth of insulation and the external air temperature drops to well below zero, I have seen the inner surfaces of roofs raining into an attic at temperatures of 10 or 15 below zero? In Scotland a few years ago we had about a week of minus 20 this generated a load of work for me, as policy holders reported leaky roofs, stains on plasterboard ceilings Etc. and it was all down to condensation, proof, no rain.

As previous, do NOT under any circumstances apply the dreaded spray foam.

 

[KenGMac]

Forgot about this!

Have a look on Floors Stair and Lofts.

There is a section at the top all about loft condensation

ken