Insulating a room - would you DIY?

[ShadowMan]

Having moved into our new home in Feb we always planned to update the office and games room behind the garages which were converted in the late 70s. Currently they are just block and brick with 25mm battens and then some wood sheet panelling. It’s not the most comfortable room in the house.

Total liner length of the walls is about 20m. I have had a quote from a builder who wanted nearly £4K to take it back to brick and then put up celotex and make good with a plaster finish. I’m tempted to do most of this myself however as it’s something I would like to do and think I could. Am I in for a world of hurt trying to DIY dot and dab celotex install?

I have asked for a pre app inspection from building control who are coming Monday so they can specify what thickness I would need etc.

Would you attempt it yourself or pay the extra to get pros in to do it.

Final spanner in the works could be a lack of a building control cert for the garage conversion. I have raised this with the solicitor who did our purchase but they are confident that as the planning permission (which I have the cert for) and work was done in 1977 then I wouldn’t need a cert as it was before they were compulsory. Waiting for confirmation in writing though.

 

[fobose]

I would get a couple more quotes to see what other prices might be on the table. If you have the time then DIY would be a good option. Have you looked in to material costs to see what it would cost you for everything you need, then seeing if the saving is worth your time?

 

[ShadowMan]

I have asked 2 other builders to come quote but neither has showed up yet. Only been a few days so will give them a chance.

material wise it’s around 20 sheets of celotex at £50 each and then some 2x4 and other ancillaries for battening out 2 walls. Probably £1500 in material maybe a bit more. Need to do a bull BoM but I would expect to be saving probably around £2k doing it myself at least. It doesn’t need to be quick as they are spare rooms really at the moment.

more worries if it’s a doable DIY project. I’m fairly competent and will tackle most things but don’t want to spend money and waste it really. YouTube makes it look easy but that is what YouTube does lol

 

[fobose]

I mean if it is just removing the old wood panels and stud work, fitting new stud work, followed by installing celotex, vapour barrier (?) and plasterboard it shouldn't be too bad. What about electrical work, is there power there already?

 

[Thebug]

Ignore read it wrong

 

[ShadowMan]

There is electrical in place already but my dad is an electrician so he will come in and add more as needed during 1st fix. Its also not on a ring we don't think just a 20A RCD from consumer so may get it updated. Also having a plumber put in new radiators and he has already dropped pipework into nearby area for access.

I'll get a pic uploaded of its current state, may start demo on monday too as having a skip delivered to clear out some other rubbish.

 

[2004typer]

Definately DIY this - should be relatively easy.

Echo the Vapour Barrier comments - will avoid any interstitial condensation between the back of the insulation and cold face of the masonry.

Don't know if your Dad is Part P registered, but if only modifying an existing circuit this is allowed (unless near a bath....but this won't be the case here).

If changing the consumer unit though, will need. Part P cert., or approval via Building Control (they'll probably step up their fee if going down this route).

 

[BlueMerle]

Absolutely a DIY project imo.

But, it would be a waste of time and money if you don't add a vapor barrier.

 

[ShadowMan]

Pretty sure the Celotex has built in VP with being foiled twice per sheet as long as joins taped properly but I’ll look at a separate layer too.

Dad is fully registered and set to update and move the consumer unit anyway as it’s quite low down and 1 years old with only 3 circuits covered by RCD. Would have been done already but lockdown happened. He’s coming next week do install some lights for me though.

I’ll keep watching some more videos. Doesn’t sound like anyone thinks it would be beyond a DIY project at least.

 

[Jez]

Done a lot of insulation like this in my time. Yep foiled sheets are a vapour barrier and just need foil taping

I’d definitely not be paying for this work, it is basic and will all be hidden by plaster anyway. Save the money and then get it professionally plastered which will cover all of your work anyway.

 

[LOAM]

I did this to ours, just trap the insulation with a regularised timber batten or CLS, tape the joints and board / skim.

I cheated a little in that we insulated between the battens so technically there's a cold bridge through the timber but tbh you get one through the frame fixings anyway, even doing it the "proper" way. We just didn't want to lose 110mm of each wall of the room.

 

[eviled]

Easiest way bay far is to keep the current battens and stick 50mm insulated plaster board on top.

the 25mm air gap will prevent any condensation or cold bridging

 

[ShadowMan]

So finally got a panel taken off the wall to see what exactly was underneath and picture below

Its 20mm x 45mm softwood with a 3mm ply panel over the top held in with panel pins. The battens are on the wall using old style clout nails.

Current thought is to build out a frame with 38mm x 63mm CLS studs with top and sole plates from the same. Will add noggins and then fill the space with Rockwool RWA45. Over the top will add 50mm of Celotex (or cheaper equivalent with a foil VLC) and then top with 12.5mm plasterboard.

Yes I will lose a few inches on each wall but think it will be worth it.

Anything I need to look out for? 2 of the 8 walls to do are external single skin so will probably put a breather membrane between the studs and brick.

 

[Sin_Chase]

Watching this with the interest. I'm wanting to DIY some internal insulation in our house on some external walls (Single block construction)

My concern is condensation between the old internal wall and new void behind insulation. Really struggling to find a definitive build method/materials amd proper use of a vapour barrier.

 

[eviled]

My concern is condensation between the old internal wall and new void behind insulation. Really struggling to find a definitive build method/materials and proper use of a vapour barrier.

I've tried 2 method; a ventilated air gap - like I have in my garage - and a vapour sealed minimal air-gap - I've done this by sticking insulated boards straight onto crick using a continuous bead of pink foam.
It has to be boards with proper foil encapsulated insulation though, and the wall can't have any pre-existing damp.

The later I actually monitored with a hygrometer in the cavity and actually saw a drop in humidity behind the boards

My garage isn't finished yet but don't foresee any issues

 

[ShadowMan]

Not much to update. Ripped 1 of the offices out to get it back to brick and had a 2nd visit from a builder to do a final quote before I make a decision on doing it myself. Walls are clean and dry and I really don't think it will be a major job to do. 50x75mm CLS with rockwool filler and a breathable membrane on the outside walls all topped with 50mm foil faced PIR and then plasterboard.

Electrician due at weekend (Dad so free) to get sockets sorted and ensure its all on a ring and change it to a 32A RCD from 20A even if we have to rewire.

Plumber hopefully next week to put in a radiator with pipes so I can work around it with the insulation.

 

[b0rn2sk8]

Are you planning to do anything with the floor?

 

[ShadowMan]

Just putting down a high tog underlay and then laminate or carpet (not decided yet). The floor is already raised 6” above garage floor so assumption is that it is an insulated slab. It’s not too cold really.

ceilings are being boarded over or redone using PIR too as there is room to lose there and may as well.

 

[Jez]

I wouldnt assume that a floor of that age will be insulated, and you would be amazed how important floor insulation is. It'd cost you very little (door threshold height permitting) to put some thin PIR on the floor (just 25mm would make a huge difference, more the better) and then overboard.

Overall, that is an easy DIY job to batton and insulate that space. Give it a go, nothing to lose. Get it plastered properly afterwards and any dodgy boarding will be covered anyway, you dont need to make a neat job of it

 

[ShadowMan]

I'll have a look but the floor was poured level with the living room so would raise floor above rest of house and create a step at the threshold. Could the floor be tackled after or should it be first to ensure it goes under the walls?