Questin for dry lining experts

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BNJ

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Slightly off topic I guess but I got to thinking about dry lining my external facing walls (house is an end terrace). The walls in question are the gable end walls with chimey breast.

My plan was to clean off existing plaster back to brick. Dot n dab with thermal boards. And then joint fill and skim. Was only planning on doing the alcove walls. Is this worth doing? Should I line the sides of the chimney breast too?

Hope this makes sense. Any tips suggestions would be most welcome. Just wondering if my proposed improvement is worth doing. Would you guys do anything different? (note: external rendering is not an option btw).

TIA
BNJ
 
would it not be easier to just pva and skim what you've got there already, if all you're after is a good finish? If the plaster you got's totally knackered then just pull it off and brown it up and skim over that. If you're looking for more insulation then jjust dot and dab over existing plaster but you'll lose some of the alcove depth ;)
 
I get a feeling from your post that I'm missing something.
Do you just have an external wall with a chimney breast that you're taking back to brick?
If so then dry line away unless there's a damp issue.
Why not the chimney breast.
I don't understand the reference to external render.

I'm no expert but perhaps if you can add some more details someone can help.

dp
 
reading between the lines like dp has it sounds to me like you got a damp problem yes? if thats the case tell us what symptoms you got and where exactly they are...theres ways round it...
 
Thanks for replies guys.

Yeah I confused things a bit with reference to render. Definitely no damp problem. Just a thermal one, so wanting to use a thermal board of some type - Any reccomendations?

Yes dpbeds, taking it back to brick. Lots of it cracked and badly patched.
Had a little read up about maintaing a vapour barrier and avoiding bridging. Am I right in thinking that when the boards are up the board adhesive and the joint fill essentially creates a complete sealed void behind the boards?

Thanks again for your interest.
BNJ
 
i presume this is a 9" solid wall, you can tell if you go outside and look at the bricks, every 3 or 5 courses you should find a row of headers these tie the wall together.
o.k so no damp problem, i presume the entire room is cold? or is it just the alcoves?
is the floor timber or concrete?
You lose a hell of a lot of heat through the floor, believe me if you compare heat loss calculations of an insulated floor against an uninsulated one you get a shock
what windows does it have? 4mm single glaze or 24/28mm k double?
the heat will travel through the ceiling just as it would the floor...
back to the alcoves, you can get thermal board like jablite (polystyrene) bonded it to it, you can dab it on or batten it...
cellotex (the greenish foil covered insulating board) has twice the insulating properties of jablite per thickness...
they should be making bonded thermal board similar to cellotex by now, try havin a search
you can batten the wall up, insert insulating board between, stick another 30mm over the top overlapping the joints if you like, this acts as a thermal break for the batttens, then screw normal 1/2" board over the top, or you could use foil backed board.
you can stick some polythene over the bricks as a vapour barrier if you like but i dont think it'll make much difference..
scrim and skim the whole lot and your there.
bear in mind though that youve only insulated a small portion of wall.
try this...https://www.tombling.com/heaters/heatloss.htm
a 9" solid wall is still able to transfer moisture through to the interior of the building so personally i would prefer the batten, insert, thermal break, board method as opposed to d+d
theres allsorts of new insulating products out there now due to the kyoto agreement, that space blanket stuff is fantastic, very thin, great for accross joists etc (an easy way of insulating a timber floor, roof rafters) but its expensive, cellotex is reasonably cheap now and very effective, jablite is pennies now but twice the thickness of cellotex for the same effect
all depends on how far you wanna go, everyone has there own prefered method, see what the others say and adjust to your budget, that'd be my advice..
 
Yes bigsegs 9" wall. Floor is boarded cira 1907. Alcoves definitely cold, previous owners fitted two rads in these to try and deal with it (I hate rads in alcoves like this).
Also got a bay window with relatively new DG (2002).

What you say makes sense, for the most part. Can you clarify about the overlapping layer over the battens please. Does this layer cover the entire wall again or just strips over the battens? Are these battens wooden or metal c sections?

Also wrt my OP, the dot n dab installation technique ensures a completely isolated void behind the boards, this is achieved by a continuous strip of adhesive around the wall edges and the bottoms and tops. How is this acheived when using battens instead? Or does this matter?

Also you say that you doubt the vapour barrier would make much difference, can you elaborate please? My understanding was that due to the new lining you create a cold wall i.e. the internal side of the brick wall, and that this is the potential area for interstitial condensation to occur. So the vapour barrier presumably prevents moist air from reaching the wall.

One other thing, I've also seen vents in skirting boards before. Is this an attemp to allow some exchange of air behind the boards or is this something entirely different?

Sorry for all the questions. Don't want to dive in and realise I've misunderstood the implications.
Thanks for taking the time to respond.

Cheers mate.
BNJ
 
vapour barrier would be advantage if you got voids, youre right in what your sayin..think lead roof/bay window...you have to create a 'warm roof' i.e. cellotex/insulation tight up under the stirling board/lead, no  voids. A cold roof is one where there is a void, e.g. normal attic space, then you have to vent it using either breather felt or ridge/facia vents..
with your wall, if you batten out at 400 ctrs, say use 4x2 cls (comes out at 90x38)...what id do is create a mini stud wall on the floor i.e. head/sole plate/studs, stand it up tight back to the wall, 3 in the head, 3 in the floor.
insert 90mm cellotex nice tight fit in between the studs.
clad the whole lot right accross in 30mm cellotex
board the whole lot with 1/2" board using 65mm drywall screws.
skim it, warm wall, no condensation job done.
your rad really needs to be under the window, it'll help to circulate the heat throughout the room, keep it above 100mm off the floor to convect effectively... top of the skirting usually ok
you can insulate the floor for a massive difference...your lookin to get the u values down, the cellotex on the wall/thermal break comes in at around 0.3 pretty good that, your window i reckon is around 1.7, your floor as it is should be around 5, not good at all...
under the floor needs to be vented correctly or youll get damp/rotten joists, acheived via air bricks front AND back of building to create a flow of air
you can lift the floor boards before you start anything and insulate it, easiest way is use that space blanket stuff, comes on a roll, like insulated ali foil, just roll it over the joists, pin it and re-board, might as well use 25mm chipboard if you dont wanna sand the floor and keep the look, you can repair any joist problems while you got th floor up too...
if you cant get the space blanket, you can get these tray type things which sit between the joists and hold insulation, usually used on flat conversions for sound insulation, will work just as well for heat using cellotex or similar...failing that stick some noggins between the joists 90mm down from the top and fit cellotex over em...reboard as normal
is the fireplace used? cos it may want some attenion while your goin to all this trouble, if its been blocked up without a vent, seriously consider venting it at the bottom and capping the chimney pot with a cowl, chinamans hat style, this will stop any damp problems manifesting..
hope this all helps, its only my prefered method, and im not an expert, its just my experience of building control, garage conversions etc...i do know it works really well though, youll be surprised
if you do the heat loss calculations for the room when your done i.e. area x u value x temperature difference that will give you your btu value for your rad...
 
skirting boards missed it sorry..
cant see how installing vents in skirting would help unless its venting a void behind it, youd expect to find another near the ceiling if that was the case...
the floor should be vented from outside, can be a periscope type vent sometimes.
there could be an air brick behind the skirting vent, could be for air flow to a real fire or a gas vent (black hole vent 9000mm2)
the only time ive seen skirting vents all over was for the electric forced air circulation heating system they used to fit in the 70's, wouldnt have expected yours to have it though..
other than that, dunno?
 
Bigsegs, I've estabished that I can achieve a total max thickness of 80mm on top of my bricks and still keep the alcoves useable. So I could follow your install method using 30mm celotex boards between studs and then cladding fully using 30mm again. Then 12mm board + 3mm finish. Do you think this is worth doing? Also any advice on how to calculate the condensation risk? I'll also take a look at that link to see if that's a viable alternative.
Cheers
BNJ
 
if you use 25mm cellotex between the studs, the studs themselves will need to be directly fixed to the wall but they can be 25x50 roofing batten treated...
then theres nothing to stop you fixing a vapour barrier over that before your thermal break, you can silicon any joins and round the edge too if you like...
as for calculating the risk, i think its written in some approved document like you get for building control, dont know the method myself and to be honest thats where id draw the line at 'worth doing'...for a couple of alcoves anyway..
As i dont know your situation i cant really advise you where to stop, but if it was my house id prolly be thinking of the room as a whole, 60mm of cellotex will give you a vast improvement over the area its applied but may not make much of a difference to the heat loss of the room, especially when most of the heat is likely to be dissapearing through the floor...
sheet of 25mm cellotex should be well under 20 quid, but it'll cost you best part of £100 in material to do the job...
surely the wall either side and beneath the window are of the same construction so you should be losing the same amount of heat through there...per square metre
i reckon £100 spent on those two alcoves will take you a while to claw back even on current gas prices..
personally id do the heat loss calculations for the whole room and work on the worst area first..
just a thought, but is the fireplace vented and if so is there a draught?
just to try and answer the direct question, 'is it worth doing?'...just those 2 alcoves, probably not in terms of financial benefit, but it wont hurt if money isnt an issue..
 
Was intending doing the bay window (also insulating the roof of this), and the sides as you suggest. So basically the two exposed sides of an end terrace being done.

Had intended on keeping fire place as servicable so really hoping to improve everywhere else. Completely agree with you wrt the floor, in fact with the skirtings off I've identified some gaping gaps betwwen boards and walls so will get these filled in definitely. Must admit that lifting boards and insulating underneath is not in the budget at the moment, but I will fix skirtings to PB using skirting plates and screws so at least I can minimise the damage if i get round to doing it.

Cheers mate.
BNJ
 
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