Problem with loft legs

Ianwzzz

In July I fitted some loft legs with chipboard flooring for a customer after they had the loft insulated. They have called me back because the insulation and the underneath of the chipboard is soaking wet. I am assuming this is because there is no air flow between the insulation and the chipboard. Has anyone else heard of this problem as I can't really see other than removing the chipboard or some of the insulation what can be done.

http://www.loftleg.com/index.php?page=what_is_loftleg

Ruski

I suggest that you call or tweet them - sounds very unusual.


Any downlighters in the vicinity? Extractor fans?


Russ

cyclonebri1

The chip board is acting as an impermeable membrane although it is actually a permeable board.
I would add a length of 4 x 2 or whever it takes under the legs to give a 2 " airspace under the boarding. I'm guessing it's over a kitchen or bathroom.

maninthestreet

Have you boarded over the entire loft, tight into the eaves???

Ianwzzz

Ruski wrote: »

I suggest that you call or tweet them - sounds very unusual.


Any downlighters in the vicinity? Extractor fans?


Russ

No down lighters or extractor fans in any ceiling in the property

Ianwzzz

maninthestreet wrote: »

Have you boarded over the entire loft, tight into the eaves???

No, only about 20 percent of the loft has been boarded and not near the eaves.

Ianwzzz

cyclonebri1 wrote: »

The chip board is acting as an impermeable membrane although it is actually a permeable board.
I would add a length of 4 x 2 or whever it takes under the legs to give a 2 " airspace under the boarding. I'm guessing it's over a kitchen or bathroom.

I spoke to the manufacturer today and they said they have never had this problem before. They also suggested putting a piece of 3 by 2 on top of the loft leg to create an air flow. Although I can see this should help, according to their spec of the loft leg the chipboard should be placed straight on top of it and the space below completely filled with insulation, as it is at the moment.

Furts

cyclonebri1 wrote: »

The chip board is acting as an impermeable membrane although it is actually a permeable board.
I would add a length of 4 x 2 or whever it takes under the legs to give a 2 " airspace under the boarding. I'm guessing it's over a kitchen or bathroom.

I have the greatest respect for your posts, but may I add a caveat. If the chipboard is type P5 - the standard green board used in new houses these days then it is not permeable. It is manufatured to be water resistant, and will withstand a fair amount of water, rain, spillages when used on site.

The posted link is flawed. When fibreglass is used for roof insulation it can breathe. This is the air flow in the roof. By laying a chipboard layer on top of the insulation it cannot then breathe. Condensation then becomes a problem, and if the boards are not type P5 they will disintegrate. With modern houses this should not present a problem, in theory (reality can be different) it is normal, or good, practice to put a polythene membrane on the top side of the plasterboard, and/or also use foil backed plasterboard.

Obviously, I have to put in a disclaimer, for some forum users delight in nit picking and point scoring. (Not your good self, I would add). Different builders approach this in slightly different ways, but current practice is towards air tight homes, which means stopping air movement and draughts into roof spaces. Current practice is also moving towards warm roof spaces - that is those without a flow of air above the fibreglass.

Gloomendoom

When I was researching boarding my own loft I read about this problem. In the absence/impracticality of a polythene membrane the solution proffered was to paint the ceilings in the house with several coats of impermeable latex based paint (emulsion.)

I have no idea if it works.

Davesnave

Gloomendoom wrote: »

When I was researching boarding my own loft I read about this problem. In the absence/impracticality of a polythene membrane the solution proffered was to paint the ceilings in the house with several coats of impermeable latex based paint (emulsion.)

I have no idea if it works.

In the 'old days' I always painted the loft side of the bathroom ceiling with bitumen!

No idea if it was right or wrong, but I didn't have any problems with the, admittedly thinner, loft insulation.

cyclonebri1

Furts wrote: »

I have the greatest respect for your posts, but may I add a caveat. If the chipboard is type P5 - the standard green board used in new houses these days then it is not permeable. It is manufatured to be water resistant, and will withstand a fair amount of water, rain, spillages when used on site.

The posted link is flawed. When fibreglass is used for roof insulation it can breathe. This is the air flow in the roof. By laying a chipboard layer on top of the insulation it cannot then breathe. Condensation then becomes a problem, and if the boards are not type P5 they will disintegrate. With modern houses this should not present a problem, in theory (reality can be different) it is normal, or good, practice to put a polythene membrane on the top side of the plasterboard, and/or also use foil backed plasterboard.

Obviously, I have to put in a disclaimer, for some forum users delight in nit picking and point scoring. (Not your good self, I would add). Different builders approach this in slightly different ways, but current practice is towards air tight homes, which means stopping air movement and draughts into roof spaces. Current practice is also moving towards warm roof spaces - that is those without a flow of air above the fibreglass.

I'm with you Furts, I only said semi permeable as I expected some "expert" to come along and say it's permeable.


But technically it is permeable, it just takes a long while for moisture to get all the way through as you and me have found when ripping out rotten green chip roofing,


Whats happening in this case is that the moisture has been found in effect trying to permeate the boarding, next stop mould followed by rot.


All I can say is that there must be a real issue below, so (a) sort out extraction down there and (b) ensure the loftspace ventilation is in top order or you will have issues later OP