Attic Conversion - Insulation Ventilation +

[queef]

Hi,

I recently bought a terraced house with an attic conversion that is not certified as a living space by uk regulations.

The roof is made of slate, has no sheeting between the baton and rafters, there is damp 'plaster' pushed into the baton and slate joints, and crammed with fibreglass insulation. Also there is evidence of water marks on the fitted plaster board and the cavity seems rather damp. There is also condensation on the slates

I plan to re-insulate and re-plaster the roof, and fit a new lighting/fire alarm circuit.

The conversion already has a fitted stairway and load bearing floor joists, so i plan to do any future work to meet regulations with the prospect of having everything made official should i choose to.

Now a few replies have come in my main question is how best to insulate my setup while reducing the condensation on my slates which has damaged previous dry-wall


So a 'few' questions:

[Concluded] 1) Should i have an air gap between any insulation and the slate, and if so how big, and what is the best way to achieve this? (ridge vents, breather 'trays' etc)

2) I have damp mortar smeared into the slates and baton, someone stated this is known as torching. Given that it is wet and i need ventilation to stop condensation can this be removed or replaced reliably, and what with.

[Solved] 3) I plan to use 6 inch rockwool roll if possible, mainly because it is breathable, is this within regulations or advisable? also is it wise to fit a breathable vapour barrier between the insulation and plasterboard?

[Solved] 4) Do i need to leave a breather space near the eaves to allow proper ventilation into the room ?

5) Am i allowed to run wiring along roof joists or do i need to find another route?

[Solved] 6) There is no way of fitting a fire door into the room entrance, no space at bottom of stairs, or fittings at the top, so i plan to make a removable 'hatch' in the space as appose to boxing off a large portion of space in the room. Will this stop me from ever having it as a proper bedroom due to fire regs?

Thanks for reading my mess of a post.

[original questions, edited after some replies]

 

[noseall]

) Should i have an air gap between any insulation and the slate, and if so how big, and what is the best way to achieve this? (ridge vents, breather 'trays' etc)

There should be a 25-50mm air gap on the cold side of the insulation. In your case this air gap should be adequately ventilated as you have no membrane. It will depend how well sealed the 'torching' is.

2) Why is the damp 'plaster' smeared into the slates and batton? and if it has good purpose can it be replaced with something that doeasnt hold moisture?

This is known as torching. It was a way of securing tiles and preventing wind, muck and snow ingress etc.

3) I plan to use 6 inch rockwool roll if possible, mainly because it is breathable, is this within regulations or advisable? also is it wise to fit a breathable vapour barrier between the insulation and plasterboard?

6" of rockwool alone will not be enough to satisfy reg's and you are unlikely to have the space in which to fit it and have an air gap. Foam board insulation is both man enough and more practical.

4) Do i need to leave a breather space near the eaves to allow proper ventilation into the room ?

Venting at the eaves detail is a typical way of introducing air into a conventional roof space or between the rafters.

5) Am i allowed to run wiring along rafters or do i need to find another route?

Probably.

6) There is no way of fitting a fire door into the room entrance, no space at bottom of stairs, or fittings at the top, so i plan to make a removable 'hatch' in the space as appose to boxing off a large prortion of space in the room. Will this stop me from ever having it as a proper bedroom due to fire regs?

Highly likely, yes.

 

[queef]

This is known as torching. It was a way of securing tiles and preventing wind, muck and snow ingress etc.

Should i replace it and what with? it is very wet and crumbly. (not to sure exactly what composite it is or whether something more resistent to water would benefit)

There should be a 25-50mm air gap on the cold side of the insulation. In your case this air gap should be adequately ventilated as you have no membrane. It will depend how well sealed the 'torching' is.

How would you ventilate assuming

a) it is well sealed
b) i remove the knackered torching completely

6" of rockwool alone will not be enough to satisfy reg's and you are unlikely to have the space in which to fit it and have an air gap. Foam board insulation is both man enough and more practical.

Headroom is not a 'big' worry, i can batton the rafters to give me a MAX of 7" rafter space, however since you reccomend foam being better, what thickness should i go for and should i use closed or open cell foam given i have no membrane?

Highly likely, yes

I should clarify that by removable hatch i mean that upon inspection there would be no hatch door, just stairs straight up, when the inspector goes, folding hatch.

From what i had explained (granted by a loudmouth) i only need worry about fireproofing the staircase, obviously to safeguard it burning down. since it follows on nearly immediately from my lower staircase he explained i would only likely need the other 2 beds and bath with fireproof doors (middle floor). he said if the attic is on fire and damaging the staircase i aint getting out regardless of a firedoor to open along the way. tbh he has a point.

It would be great if someone can give a direct answer on that, need to be sure.

 

[freddiemercurystwin]

You will need a door between the escape route of the house (ie the landing) and the room in the loft. this can be at the top or bottom of the stairs subject to ensuring your stair complies with Part K of course. May need to re-jig the stairs or use a (shudders) spacesaver jobby. http://www.planningportal.gov.uk/Pp...portal.gov.uk/uploads/br/BR_PDF_ADB1_2006.pdf paragraph 2.20b
Folding hatches are not really doors.

 

[queef]

Thanks for the link with the fire regs, i will have to look into this a bit further.

I have about a foot free space at the bottom of the stairs before it opens to the landing.
The stairs entering the attic hook back and form a 'c' shape from overhead view, to clear space for a door at the bottom i would need to lose 3 steps from the bottom, drop the stairs, and add 3 to the exit, aswell as modifying floor beams to suit.

Is this what you meant by re-jig?

I really want to avoid boxing in the top of the stairs, i will lose too much room and it will just seem dark and orrid when you walk up.

Cant use spacesavers, well, not unless i want to buy my dogs titanium legs, they will try it.

 

[freddiemercurystwin]

Re-jigging the stair (well replace probably) to get a door at the top or the bottom is exactly what I meant. As mentioned you could look at a spacesaver stair. TBH its hard to say without seeing plans of your house, fitting the stairs into loft conversions is always the tricky bit unless the house is big to start with. Frankly though, it's not all that uncommon for loft conversions to simply not work due to space restrictions. I have had the displeasure of giving the kiss of death to a fair few loft conversions when the client, full of ambitious thoughts of luxurious master bedrooms with spacious ensuites away from the kids realises that their seemingly big loft is only big enough to fit a bed and precious little else.

 

[jeds]

If I read this right you plan to fit enclosed insulation beneath the exposed roof slates - i.e. with no underslate felt/membrane. First off, this is not recommended and runs a high risk of condensation forming on the underside of the slate - which has nowhere to go but drip down onto the insulation. Ventilation will help but it will need to be very, very good ventilation and even then there is no way to guarantee eliminating condensation altogether.

If you decide to proceed with this anyway my advice is be double careful with the ventilation path and also fit a 1200g polythene vapour layer between the plasterboard and insulation. The vapour layer should be continuous if possible and if not make sure the lapped joints are well sealed. I would also seal the gaps between insulation with aluminium vapour tape before fitting the vapour layer.

 

[queef]

Freddy:
Space is definitely my big pain in the backside, the house is narrow, but long, means my stair exit is pretty much central in the attic, butted against one side. I cant use spacesaver's, i have 2 large dogs and they will hurt themselves out of curiosity.

Im reconsidering whether to go for the '3bed' classification, if i class it as a 'store room' i can just put a folding door at the bottom and still re-wire and plaster it up right?

It isn't ideal, but it will at least allow for a good sized room with an open feel, as appose to an official room that is smaller and dark. Tis going to be a tough call to make over a fire door :S will have to look into how much i stand to profit on resale with both options.

Jeds:
Hi, that would explain why the torching is damp and crumbled, as there is fibreglass fitted currently between the slate and plaster with very minimal air gap.

I don't mind what technique is used to insulate the roof, as long as i insulate it in a way that will minimize any damp.

Do i use closed or open cell foam insulation for these conditions?
Also how do i best ventilate the tiles?, i.e roof vents, ridge vents etc
Do i keep the torching on the tiles, replace it, or remove it? (see my first reply)
Am i able to install anything between the insulation and slate to combat drips?


Thanks

 

[jeds]

Unfortunately, without stripping the tiles and fitting a membrane there will always be a risk. You are best off using PUR insulation which is closed cell and forms it's own barrier. The joints will leak vapour so seal them as best you can and the 1200g vapour barrier will reduce the amount of vapour that gets as far as the joints. That's about all you can do internally.

Above the insulation, leave the best gap you can and make sure there are no obstructions. The eaves should be vented into the gap and either up and over the ridge to the opposite eaves or preferably a vented ridge.

The problem with slates is that they sit very flat and there is little ventilation between them. Obviously they get very cold in winter so as soon as vapour hits them it condenses. Normally this would drip onto the membrane and be carried away but you don't have a membrane so you can see what is going to happen.

I have seen the suggestion before of fitting membrane trays from below. this would involve stapling breather membrane between the rafters about 25mm below the underside of the slates. It works on the basis that you obviously don't get 100% cover but it does provide some protection. I've never seen it done myself so I wouldn't like to say how succesful it would be.

 

[queef]

.

 

[queef]

Since i have no headroom issue would this be any more beneficial?

use the full rafter space, 3" as an air gap.
put permeable membrane on the inner side of the rafters?
fix some baton over the membrane onto the rafters.

Into this new space fit 65mm PUR closed cell insulation, tape up all seems,
then line again with 1200g vapour barrier.

finally finnish with foil lined plaster boards?

Thanks

 

[queef]

After having slate breathers recommended it highlights this thought:

Is the mortar, or torching on the back of the tiles contributing to the condensation build up, and will removing this wet mortar give my roof the extra air circulation it needs as appose to eaves and ridge vents without having to large of an impact on insulation or structural integrity?