Plastering soft red brick

[brk1]

My old house is made out of soft reds which I know suck up the water like a sponge, whoever did the work in my house some 20 years ago came from the O.K Corral , Yee Haaa, ridem cowboy. Some of the work has to be seen to be believed, I know most of it stayed on the wall all that time ,it wouldn't have done had it not been tiled or had kitchen units screwed to it though.What's the best way to prep the walls ,then the best way of plastering it afterwards, the walls seem fairly dry, I've sorted out where the damp was coming from, those Texas rangers cut off the old lead toilet supply, did a nice special "Whack it flat with a hammer" routine, so how many years its been leaking I just don't know, I just couldn't fathom out where the hell it was coming from until I decided to stick an injected DPC in the wall and go 1m high with waterproof render in the lobby, did I come across a missing brick and I could see water dripping slowly through the hole, anyway, that's all solved now.

All bricks will be as clean and dust free as humanly possible,
1.What do I seal them with for best results, PVA mix or SBR ?
2.Scratch coat first left how long to harden?
3.Top coat left how long before skimming?
4.Waterproofer added to which coats to stop any future damp?

Any help would be greatly appreciated

To try and keep this long post any longer I've done a separate post about the floor screed

 

[PrenticeBoyofDerry]

If you have injected a DPC, you should be using Dri-coat (spec)on those areas.
Normally the the base coat can be worked on quite soon after applications, once it has took to the wall and starts to set you can work on it.
A double application of multi-finish can then be applied, first coat about 2mm in thickness, spread evenly then flattened before it sets about 15 mins from first applied area.
Then a second coat slightly wetter than the first coat and about 1mm thickness. Again 15mins then flatten, then wait for it to take to walls this is usually a finger test. Could take a while depending on drying conditions and environment.
Then you can do a wet trowel, depending on what the area is decorated with, you then have an option to dry trowel.
I generally don't dry trowel on tiled or paint areas.

 

[brk1]

Thanks for that answer, I wasn't going to inject a DPC along the kitchen wall, now that lead pipe leak has been sorted,I don't think I'll have any problems any more, I only injected the lobby walls because they were the original 4" soft red outhouse walls that had no DPC, the other side of the lobby is 9" solid reds and Bill and Ben just straight plastered over the bricks,it hadn't stayed on so I took off the 1m high band and did a waterproof render mix, when I actually took the screws out of the skirting boards, they were still shiny bright zinc like the day they went in some 10+ years earlier,so it was overkill on my part in the first place, apart from not being able to find Dri-coat locally it seems to be £20 plus a bag, for 2 bags of that I can totally plaster and skim the whole kitchen and still have change, I have the sand,the waterproofer etc, just need some fresh cement to complete the materials, and I'd need more than 2 bags to do the 3 walls needed

 

[peaps]

Old redbrick needs lime render. Don't seal the brick and don't use pva.

 

[brk1]

Please explain the use of Lime render , surely that's what was on there in the first place,it peels off in sheets with no banging at all, just put a chisel to the wall and rub and it falls off in seconds,I know it's been there 100 years but the odd bits it was patched up with some 28 years or more ago were still stuck like s*** to a blanket, they actually pulled the facing of some of the bricks,I'm interested in all reasons for using whatever is best

 

[peaps]

Please explain the use of Lime render , surely that's what was on there in the first place,it peels off in sheets with no banging at all, just put a chisel to the wall and rub and it falls off in seconds,I know it's been there 100 years but the odd bits it was patched up with some 28 years or more ago were still stuck like s*** to a blanket, they actually pulled the facing of some of the bricks,I'm interested in all reasons for using whatever is best

Lime is breathable and flexable so you won't get damp problems and the bricks won't "blow" due to the render been harder and won't flex. Your walls need to breath to prevent damp problems. Back when it was built lime was used to prevent damp amongst other things.

 

[brk1]

Well explained, but won't lime plaster take about 2 months to dry, I was hoping to have the kitchen fitted before Xmas and get my house back to a habitable hole ,would not a Sand,cement and lime render be suitable ?

 

[peaps]

Well explained, but won't lime plaster take about 2 months to dry, I was hoping to have the kitchen fitted before Xmas and get my house back to a habitable hole ,would not a Sand,cement and lime render be suitable ?

No need to use cement if you use NHL 3.5 and it sets in much the same time frame as cement. If you use NHL 2 (bagged lime) in a 6.1.1 mix you will reduce breathability and flexability.

 

[brk1]

I'll see what I can source around me locally, from what I've read from one suppliers data sheet, a 2:1 sand/lime ratio for backing coat then 2.5:1 top coat Sand/lime mix then trowel up as flat as possible ,then no skim coat ? then I would need special lime paint to decorate it with when dry, I wouldn't have to go to the extremities of adding hair would I? What is it like for tiling over,same as sand/cement render ? Would the first coat still be a scratched coat ?

 

[joe-90]

The way gas prices are going I'd forget about rendering and bang up insulated plasterboard. It's the common sense thing to do these days.

 

[brk1]

Because there will be a gas pipe in the wall, and insulated board would then make it a cavity wall, plus I've got several kitchen units going on that wall and the soft back of the insulated board always compresses when individual wall unit brackets are fitted, they never really tighten up properly unless on a solid wall, also I know it's not the best option but this wall is the party wall and not external so isn't quite so cold as the others

 

[peaps]

Because there will be a gas pipe in the wall, and insulated board would then make it a cavity wall, plus I've got several kitchen units going on that wall and the soft back of the insulated board always compresses when individual wall unit brackets are fitted, they never really tighten up properly unless on a solid wall, also I know it's not the best option but this wall is the party wall and not external so isn't quite so cold as the others

I would board it if I was you. I can't see the lime render going on the way it should to be honest.

Lime is a fine art and every job is different. Mixes vary even the area you live will dictate how the job is to be done.

If you use NHL 3.5 at a ratio of 3/4 sand and 1 lime you don't need to use hair. You can control shrinkage by taking care how much warter you add to your mix but this is somethng you learn with experience. Every wall is different. Lime will shrink dramatially in hot weather and break down in freezing temps. So in the summer you need to keep damping down and in winter you need to protect the lime from frost.

 

[joe-90]

Because there will be a gas pipe in the wall, and insulated board would then make it a cavity wall, plus I've got several kitchen units going on that wall and the soft back of the insulated board always compresses when individual wall unit brackets are fitted, they never really tighten up properly unless on a solid wall, also I know it's not the best option but this wall is the party wall and not external so isn't quite so cold as the others

You put battens where you are hanging cupboards. Simples.