Hi I have registered here because i have been looking over the green forum for ages and cant find what im looking for. Basically we have a two bed semi thats been converted to a 3 bed. 1945ish build we are looking at gutting the whole house as all the plaster is blown. We are planning on using standard plasterboard through the house. Would there be much to be gained by using polystyrene backed board if theres already a wall cavity? Im more worried that by retro fitting thermal board as iv seen people saying things can become too airtight and also sweating back into the cavity.. So basically im asking should i stick to 12.5mm board and is there any risks in using good old plasterboard through the house with exception of the bathroom?
What is the external quality of the house like ? If the outside needs redecorating/ rendering etc. You will get very good results from insulating the outside. There are many products that can be used inside with varying results and obviously higher costs. I recently relined a very cold and consequently damp bedroom with high density backed plasterboard and the results were very impressive. Boards can be applied to both the walls and ceiling and can be fixed either directly or via battens. Depending on the work planned and floor finish you may want to consider some form of floor insulation as well The problems with "sweat" is normal to poor ventilation and things like not installing vapour barriers where they are needed.
Do you mean removing all plasterwork in the house and dot n dabbing new plasterboard on to the walls? Personally, I'd get a good plasterer in to do "proper plastering" eg a bonding coat then a finishing coat. If you have stud walls anywhere in the property, it's possible to remove the old plasterboard/ lath and plaster and cover these with plasterboard. If you dot n dab the walls , the door frames are going to need either changing or extending (to accommodate the extra width dot n dab takes) It's possible to use thermal boards on the external walls to add insulation, but as well as dot n dabbing, these will need mechanical fixings to comply with regs.
Door frames are being ripped out so that wont be an issue. There was old yale locks fitted in interior frames! Outer house is fine other than needing a bit of pointing. I have seen council houses here fitted with that new thicker rendered insulation but not sure we could have it as the overhang on the roof might not be enough. Oldschool plastering might have to be an option on the staircase as if we boarded it with plasterboard then it going to overhang past the staircase carcass. Could be an issue
Just had a quick look at cost of external and a figure thrown out there of £100 m2 thats nuts. Realistically i could only go around 30mm thickness so im just a bit worried it might not be worth it? And as i say the hallway might be impossible to use due to depth.
If cavity wall, then insulated PB on external walls would be a good upgrade. Dabbed plasterboard elsewhere and like you say, may need to wet plaster staircase to prevent overhang of the stringer. Opinions always mixed on dabbing PB's though...
So its worth doing even though it cant be done everywhere. Dreading the staircase. Going to get someone in for that il just do the donkey work. I dont mind dabbing the boards then mechanical fix after. Im guessing you still do a perimiter bead of adhesive around the board like you would regular plasterboards
GJ, as said above. If you are removing all the old plaster -a hellish job - then you'd be NUTS to not use insulated p'board on all the external walls. If space is an issue, then use the thinnest stuff - only around 30mm total thickness (and you're already gaining 15mm from removing the old plaster...). If you can, go slightly thicker - say 40mm total. There is no need to go any thicker. Ordinary plain p'board on internal walls. Look up D&Ding to make sure you have the process right - yes, a perimeter bead, but lots of spaced dabs too. Ditto for ceilings - use the thinner insulted stuff - 25 or 30mm total. For floors, mainly try and reduce draughts through floorboards and around perimeter of walls behind skirtings. This will transform the insulation value of your house.
As DA says, will transform insulation value. It's important that you make sure that there are no damp issues before you start though...no point 'painting over the cracks' etc. Problems usually arise when people have used gypsum based plasters on solid walls, i.e no cavity as they will soak up moisture leading to damp patches. Cement based renders are used as a backing coat internally in these scenarios, to prevent moisture penetrating to the skim coat. Ventilation is really important. Any air bricks at ground level must be clear. Blocked off chimneys ideally need venting and good to have trickle vents on your windows. If you haven't dabbed boards before, then I suggest you don't start with the insulated ones...get a bit of practice on some of the internal walls first to get the knack.
Thanks for all the replys. Been a great help. Yes all the house is being done. There is an issue with ground level on the wall with the staircase, quite damp there but i plan to sort this in the next couple months. Just needs digging a trench out. The hall will be left till this has dried out. The other thing i noticed is how the interior walls are tied into the interior side of the external walls, theres big baps where it needs mortaring back in. As well as numerous mortar missing out the brickwork. Like where the old skirting had wooden packers knocked into the bricks. I take it these are all things that are critical prior to insulated boarding. I have done plenty of normal boarding over the years. Just not thermal. Other issue you guys bought up as the windows are brand new updtairs and dont have trickle vents fitted. We were told its best not to have them because it helps keep the frames free from mould and ingress. And it has a second lock/catch so the window can be left partly open. Is this going to be an issue if i use them?
Right other issues aside i still need help with this thermal plasterboard. I can get knauf 30mm expanded polystyrene from my local builders very easily and they dont charge much for delivery on weekends. I dont think it has a integral vapour control layer as its not the "plus" range. Is this going to be an issue? Its for my exterior walls B and q sheets have integral vcl but only do home deliverys on week days and i need something i can get weekends
Forums
Facebook
Twitter
You Tube
Instagram
Shop