Roofing felt advice for loft

[heskey]

Hi,
My house was built in the 1940s and the roof is made of slate but has no felt or anything on it, i have noticed that you can see daylight through some gaps in it. We are looking at doing the room up into a storage room and insulating and boarding the room up, but unsure what the best thing to do with the gaps in the roof? any advice would be welcome. Would it be possible to attach felt onto the slate from inside the loft??

 

[Alastairreid]

hi,
best to get your roof repaired before doing any insulation works.

 

[heskey]

it def does need repairing but just looking for a cheap option, instead of getting roofers in to do it.

 

[gday2uk]

No real cheap option (apart from doing nothing) but the best option would be to reslate putting breather membrane under slates.
You could get someone in to spray foam onto inside of slates to insulate them but it's not very good and will cost you more in the long run when you come to re-roof.
Is there actually a problem with the roof i.e. leaking? Or did you just panic on seeing daylight through gaps? If there are no leaks then don't worry about it, if you have a leak in the future repair the slates then.
Count yourself lucky you have good ventilation in your roof space

 

[heskey]

hi, there are no leaks from the roof, and when we do the room we are going to insulate it with kingspan board and then put plasterboard on so it looks better. But in two years I have never noticed any leaks from the gap.

 

[Alastairreid]

I think the only solution for this problem is applying roof coatings with its rubber or elastomeric but it can save ur building

check out.

*********************

 

[gday2uk]

I think the only solution for this problem is applying roof coatings with its rubber or elastomeric but it can save ur building

check out.

********************************

On top of the slates or under them

 

[alittlerespect]

Hi there is an old saying that goes along the lines of 'if it ain't broke it don't need fixing'? Well, from what you've mentioned the roof is watertight and its doing its job, so why mess with it!

I would assume that your rafters are 100 x 50s (4" x 2" in old currency), as a suggestion you could use a 'jablite insulation (polystyrene) between the rafters , you will need to make sure that you leave an air gap for ventilaiton between the slate roof and the insulation - 25mm (1") would suffice, on the basis of 4x2 this would allow you a maximum thickness of no more than 75mm for the insulation - to avoid condensation problems you will need to fit a vapour barrier over the rafters before fixing the boarding directly to the underside of the rafters, the vapour barrier stops the warm air which holds more moisture than cold air coming into contacting with a cold surface where the temperature drop would cause the air to reach its saturation/dew point, condensation in such situations can be pretty extreme.

Or you could use a urethane board which has slightly better thermal resistance and is vapour resistant - but check out the cost. Or if cost is an issue you could reduce the insulation down to 50mm thickness, but you wouldn't want to go any lower than that.

 

[heskey]

how would you fit a vapour barrier?

 

[Alastairreid]

in this case 500 guage visqueen stapled over the trusses would suffice.

 

[alittlerespect]

Hi!
I would recommend that you visit visqueenbuilding.co.uk and download their data sheet for installation instructions. Other than that Visqueen will do a very good job.

 

[Milo19]

One could argue why bother plaster boarding a loft space which is only used for storage.....Im sure i've read somewhere that a surveyor questioned the plaster boarding in a loft space as to whether it was a botched loft conversion.

If its only used for storage of xmas decorations and other bits and pieces, don't bother. Save yourself some cash and just insulate and board it.