New House rendering+Plastering

[headworx]

Hi all,

I have just bought a house (built in 1930's) and most of the walls were blown so I have got all the plaster off the affected walls and planned to board and plaster them.

So far there is the entire bathroom which I was going to pb, plaster then fully tile (which has 2x outside walls using aquapanel where the shower wll be), the hallway, 1 wall in the living room and a couple of bedroom walls (one being an external wall which is now internal due to a double extension).

After reading a lot of posts on here last night, I've discovered that most recommend the old wall be rendered first to stop damp and ephervescense whatever its called lol.

tbh I'd never heard of this before and only thought rendering was for outside. I've no experience with this kind of stuff so am a 'noob'.

What I'm asking really is, does this apply to me and if so, is it all the walls I would do or just the outside ones?
Also how thick would I do this as I wish to plasterboard and plaster on top of that so dont want to come out too far.

I presume the mix is 3-1 sand-cement with some pva/plasticiser added?

I know I'm new to this but want to use this house to get some new skills, well moneys real tight too as I stretched to get the house (will be nice when it's done tho).

Thanks for reading.

 

[headworx]

A fair amount of views but no replies - am I asking a dumb question or something?

 

[jrplastering]

ok have you compleatly stripped all of your exterior walls? if you have it might be worth upgradeing the insulation BC usually require you to do so if it hassent been done already.

you can sand and cement the walls with a 4.1 mix with waterproofer. then dot and dab ontop as your a novice i think this will be easier than you trying to float the wall out yourself with 2 coats.

as to how thick to put it on i depends on how true your walls run but you want to be looking at about 10mm.

try to get the walls roughly straight with this coat and run a render scarifier over it to give the d&d a key, make sure you dnt scratch it right back to the brick though other wise youll weaken the bond.

alternativley you could clean the brick walls up then paint them with blackjack then drill and fix timber to the wall levelling up as you go along. then insulate the gaps between the timbers and screw plasterboard over the top.

the choice is up to you. im sure the guys on here will have other methods for you to go aswell.

hope that helps

 

[Micilin]

[
4:1 render (that's 1 part OPC) with a waterproofer. Stay away from PVA.

Wall clean, dust free, should be enough key if back to brick.

IF you are stcking gboards to it, just make sure you have a decent coat on to seal up the bricks - ie 8-10 mm

You can scratch this to help adhesion of boards, but make sure you only scratch the surface , ie don't break thru to the bricks .

Your walls will have an old slate DPC, so you may get rising damp anywhere, but you shold be able to spot this by now.

I would definitely do this wherever you have had damp and personally would do it on all external walls

[/b]

 

[Micilin]

jrplastering - sorry, was typing min when you posted yours!!!!!

 

[jrplastering]

haha beat ya

 

[Richard C]

A fair amount of views but no replies - am I asking a dumb question or something?

No not at all but you just have to wait for those with the knowledge to come along & most of us do have day jobs ya know . You do need to be a little patient & sometimes it pays to just “bump” the post but yours does seem to have been missed, at least by me anyway. It’s also worth remembering that a little digging in the archive will answer most general questions & you can then concentrate on the specifics. The advice you’ve already got from the other pro's is sound & covers most of your questions so I’ll just chip in on a couple of things.

I have just bought a house (built in 1930's)

Is it solid brick external walls or cavity construction?

most of the walls were blown so I have got all the plaster off the affected walls and planned to board and plaster them.

As already pointed out, if you’re stripping more than 24% of plaster from external walls, be careful that your LABC don’t find out or you could land yourself with a hefty bill upgrading the insulation; but it’s not a bad idea to do that anyway. Unlikely they will find out unless you tell them but something to watch if you’re having other work inspected, several have been caught out!

Hi all,
So far there is the entire bathroom which I was going to pb, plaster then fully tile (which has 2x outside walls using aquapanel where the shower wll be)

If your going to tile don’t plaster, it’s not necessary & will reduce the maximum tile weight you can hang; this could be a problem if you intend laying large format tiles. Only use Moisture Resistant plaster board in a bath/shower/kitchen room but it will need priming if your half tiling & plastering above. Aquapanel will be fine for the wet area but how do you intend to fix it? Read the Tiling Sticky & Tiling Forum archive posts to avoid making mistakes which could end in tears & loads of money.

After reading a lot of posts on here last night, I've discovered that most recommend the old wall be rendered first to stop damp and ephervescense whatever its called lol.
tbh I'd never heard of this before and only thought rendering was for outside. I've no experience with this kind of stuff so am a 'noob'. What I'm asking really is, does this apply to me and if so, is it all the walls I would do or just the outside ones? Also how thick would I do this as I wish to plasterboard and plaster on top of that so dont want to come out too far.

If the outside walls are solid as opposed to cavity, it’s those you need to be very careful with. Don’t just dot & dab them, you need to provide either a waterproof membrane or use a waterproof render & some insulation or;
a) you could get damp transferring through
b) you will create cold spots where the adhesive dabs are which will usually cause condensation.

A bit more research may be advisable to decide the best solution in your case; plenty in the Plastering Forum archive posts.

Hi all,
I presume the mix is 3-1 sand-cement with some pva/plasticiser added?

3:1 is far too strong for a render mix 4/5:1. Don’t use standard PVA, it’s not waterproof; you need a proprietary water proofer (usually SBR based) to create a waterproof render.

 

[jrplastering]

i forgot to say dnt use pva as richard has just said...............sooo....yeah.... dnt do it.
i was thinking of an integral waterproofer.
i like the travis one never had any problems with it

 

[headworx]

Thanks all for replies

Just a couple more to clarify (sorry if I'm being thick but I just want to make sure I do it right as I'm limited for funds and dont wanna have to redo it).


@ Richard

Right, the bathroom is back to brick.
I intend to have the floor and all walls tiled - The walls being the large 60x30 most likely.

When you say dont plaster or plasterboard if putting on big tiles, what should I do insead? Should I render it?

Also when people say dont PVA, do they mean dont put this in the mix or dont PVA the wall first (or both). (I have PVA'd a couple of the walls that are bare brick and was going to plaster them after another coat of PVA, is this wrong?).

I've also just removed the ceiling on the bathroom as it was a right mess and part of one interior wall (not load bearing) and will be replacing it with the aeriated blocks. I took some of the wall down as there used to be a aering cupboard which is no longer needed and wanted to give the space back to the adjacent bedroom. I think I will end up renewing the entire wall though tbh.


Also whats OPC and gboards?

 

[Richard C]

Sorry about the delay in getting back, been a little busy this weekend & yours is a little more involved.

I intend to have the floor and all walls tiled - The walls being the large 60x30 most likely.
When you say dont plaster or plasterboard if putting on big tiles, what should I do insead? Should I render it?

A water proof render is usually the best route on solid external walls but in this case I would not advise it unless you want to wait up to 4 weeks before you tile. But you also have an additional problem in that render will be marginal & for tiles the size/weight you’re using. With tiles that size/weight you should be mechanically fixing a decent waterproof tile backer board but on the solid external walls your going to need some form of vapour barrier behind them or your likely to get all sorts on nasties growing behind.

Plasterboard is out as bare plasterboard will only take 32 kg/sqm but, if you plaster, this drops to 20 kg/sqm including up to 4 kg/sqm for the adhesive; check your tile weight, I would think they are likely to exceed the maximum for PB & plaster. You must use a flexible cement powder adhesive of the correct type for your tiles, if you try & use tub ready mix they will never stick let alone stay on there.

Also when people say dont PVA, do they mean dont put this in the mix or dont PVA the wall first (or both). (I have PVA'd a couple of the walls that are bare brick and was going to plaster them after another coat of PVA, is this wrong?).

Don’t use PVA on ANY tile base & I wouldn’t put conventional PVA in a render mix; for waterproof render you need to use a waterproof SBR additive. PVA is generally used as a sealer/primer before plastering but on bare brick its better just to damp them down.

I've also just removed the ceiling on the bathroom as it was a right mess and part of one interior wall (not load bearing) and will be replacing it with the aeriated blocks. I took some of the wall down as there used to be a aering cupboard which is no longer needed and wanted to give the space back to the adjacent bedroom. I think I will end up renewing the entire wall though tbh.

Aerated blocks will require special treatment before tiling, check the addy manufacturers recommendation, usually best to fix tile backer boards & tile directly onto those. A point to note is that if you decide to use stud between a room with a w/c & another habitable room, it must be sound insulated to comply with B Regs.

Also whats OPC

Ordinary Portland Cement

and gboards?

Never heard of them – think micillin just made a typo with an extra “g”; should read sticking boards.

 

[Micilin]

Never heard of them – think micillin just made a typo with an extra “g”; should read sticking boards.

Sorry lads, Richard is spot on, as usual!

Blame years of substance abuse, mostly render and gypsum......