ancient house - plastering inside

[karaman]

hallo all,

bought ancient cottage which has been neglected for a long time. no damp proofing and cant afford to have it done just now. removed half the plastering inside up to where the bricks were damp and allowed them to breathe all summer. outside work is on-going to stop water seaping into foundations.

read lots on what to use to replaster but am going gaga especially as having finally decided on the materials to use, no-one appears to stock them. advice from diy places is lamentable.

please can someone help? i need simple instructions on what to use: water-repellent plaster or plaster that 'breathes' ? do i need a bonding agent? the bricks are not divided by mortar, its like sand and something that just crumbled away when i cut it back a little. will use a wood-burning stove - will that lead to condensation?

fed up with looking at bare bricks in what is supposed to be a lounge, need to start a.s.a.p!

any advice appreciated.

karaman
the spirit never dies
+++++++++++++

 

[TonyV]

hallo

Hello Karman - how old is your cottage? and what build?

 

[RedHerring2]

I recently re-plastered about 4 metres square in lime plaster.

before building the stairs.

As you can see it's a stone built house with mud/cob/clay mortar.
I used a PVA/water spray to the cleaned/ brushed walls after scraping out the joints a little.
Then hydrated lime and sharp sand (0-3mm), 1:3 after filling in any large holes/indentations with the same mix and stone/slate where required.
Difficult to give a depth because it varied from almost nothing to perhaps 25mm due to the variation in the wall.
Damped down each day for a week, then second coat, same mix. Unfortunately I couldn't get any other sand so used the same for second coat. Next time I'll sieve the sand to reduce to about 0-2mm.
But in the UK I assume plastering sand could be used.

Damped down each day for about a week.

I suspect that a wood burner will assist the ventilation due to the air requirements, depending on design, therefore, I think, it should help to reduce condensation.

I read somewhere on internet that stone walls dry out at a rate of about 1 inch per year. My walls are at least 700 mm thick and up to a metre in places. If my walls were wet, I reckon it'd take about 30 years to dry out completely

 

[trowelmonkey1]

i think you've got to go with lime plaster here, when you say 'water-repellent plaster' i assume you're talking cement based and possibly with a waterproofer in? Cement would be a bad idea based on the mortar you have, the plaster should be no stronger than the substrate otherwise you'll run into problems, and as your walls are solid stone breath-ability will need to be considered.

the next question is whether to choose a lime putty based render or a hydraulic lime which sets like a gypsum plaster would.

Redherring2, you say you used hydrated/builders lime? i have to admit my lime knowledge/experience is limited but i had no idea you could use just hydrated lime and sand without cement.

 

[RedHerring2]

As I undersatnd it, and I'm no expert, hydrated lime is OK for inside. Outside you'd need a feebly hydrhaulic lime at least.

I used Saint Astier hydrated lime, Decor-Caux LC90, I think it was.. They have web sites with a fair bit of info'.

Most other advice seems to suggest it must be a lime putty but the instruction on the bag were quite specific, 1:3 or 3.5 l/s and water. Mixed in a cement mixer.
No mention of lime putty unless using it for a lime wash.

 

[karaman]

hallo,

your place similar to mine - mud walls i got i think. (but i bet your walls are not as wet and i wish my beams were same colour, something else that needs doing)

advice appreciated. will go for the hydrated lime + sand to fill in the joints. mixed with the 3.5l water, what consistency should i end up with - runny yoghurt or thick custard? i shall follow up with ready-made mix of stuff i found that says it 'dries out walls and allows them to breathe' . sounds good to me. like yours, depth will vary. questions:
- why wait a week between coats?
- how do you 'damp it down'? cant wait for it to dry, so why damp it?

the water-repellent stuff - i have found out - is meant for use outside under the level of the damp-proof course. but i dont got no damp course on this side of the house and leaving outside work for next year.

thanks

karaman[/u]

 

[RedHerring2]

Looks like you can't sleep, are you worrying about it that much?

My advice is only based on what info' I've gleaned from the internet, etc. I have no training in lime plastering or any plastering.

General advice on internet is to wait a week for first coat to go off, bearing in mind that a lime only plaster will take months to fully cure.

Damping down with a spray bottle of water, not so much that the water is running down the wall. Just like you do when you're plastering and wetting the walls.
The purpose of damping down is to slow the drying process to reduce the risk of cracks developing. But it has to dry to cure, i.e. the curing process is a reaction between the lime and carbon dioxide. it can only do that when it's dry.

The feebly or eminently hydraulic lime is for use in any situation that may be damp or wet, e.g external rendering, underground, etc. It has a curing process that is slightly different to the hydrated lime. I think it cures in a similar manner to cement, i.e. a reaction with the water. But I'm not 100% sure on that.

I tend to mix the first coat a little thicker than the second coat (never done third coat yet), say to a thick custard type consistency, then second coat to a runny yogurt consistency because the second coat may be thinner than the first coat.
In my case the second coat thickness was determined to an extent by the sharp sand that I used.

I guess the waiting and slower process is why it was replaced, in general, with cement and gypsum products.

If you've several walls to do, you may find that by the time you've first coated all the walls you're nearly ready for second coat. That's about the speed that I work anyway.

Incidentally, them's new joists. The house is basically new from the top of the walls that you see all the way to the roof, except for the crook frames.

Look it up in the 'Your Projects' forum under House in France under renovation.

Just realised that you may have misunderstood what I'd said before.

That was a mix of 1 lime:3 or 3.5 of sand, I didn't mention 3.5 litres of water.

A question I'd ask is: why are your walls so wet?
If it's 'cos of the poor state of the external wall I'd do the outside first, repoint or whatever. If it's for another reason I'd sort that out first.

 

[karaman]

hallo,

your place looks smashin'

was thinking as you say, theres such a lot to do, by the time i finish, i can start the second coat. deep joy. how do you tell its ready for a dose of dampening or do you do it on the hour every four hours, etc?

you did not confuse me, i did that all by myself. 3.5 l/s is lime to sand not litre...silly wallette.

walls are wet as house (about 100 years old) neglected for long time then stood empty for a while. gutters leaky, path around house slopes INTO foundations. after the rains last year, its a wonder the place has not floated away! too late to fix walls outside, will be project next summer. by end this september, fixing concrete path so it slopes AWAY from house and installing new guttering. that will have to do.

i'm all set now, just gotta get on with it!

thanks

karaman

 

[RedHerring2]

Well, Bon courage to you.

But I have to repeat what I said before: I'd sort out the problems outside first.

Damping down, probably once or twice after work the first day, then maybe twice a day for the first couple of days, then just once a day for the rest of the week.
Use a spray bottle.

After the end of the first day you'll find it firm to a palm pressed onto the wall.
By the second day you'll find that with very firm pressure you can very slightly indent it with a finger.
After that you'll find that you can scratch it with a finger nail for many days, so be careful with furniture etc 'cos it easily marked at this time.

Don't forget to scratch the first coat. You can do this several hours after finishing or even the next day.

Incidentally, from my understanding:
Hydrated lime has the most breathability,
Feebly hydraulic lime some breathability
and emminently hydraulic lime the least breathability.

 

[karaman]

hallo redherring2,

just been to buy my materials and was defenitely told to add cement to the lime and sand mixture but the guy did not know why to add it, its just that its the 'normal thing to do'. just checking you did not add cement to your mixture - would like to forego the extra expense if not necessary.

thanks

karaman
the spirit never dies

 

[RedHerring2]

I did not use cement in the lime plaster.
Hydrated lime, sand and water only. Except for the diluted PVA that I sealed the walls with before starting.

There are, I think 3 basic methods, with variations on the themes:
1. Cement/sand render (may have lime or other additives in, may be plastered over ) which seals in the moisture,
2. Lime plaster (no cement) which allows the walls to breathe and flex. (Lime putty, hydrated, feebly or eminently hydraulic lime)
3. plasterboard, Dot&dabbed or on a frame. Plasterboard may or may not have insulation &/or DPM attached, or may be separate.

All seem to have their proponents and detractors and I think it's difficult to get a balanced, unbiased opinion.

But I will repeat, I'm only a layman with no training. I think I'm accurate in my summary of the methods and hydrated lime plaster works for me, on this occasion.

Maybe one of the spreads on here will either verify what I'm saying or if they're unsure, perhaps they'll give it a try and offer their opinion.

 

[trowelmonkey1]

don't forget gypsum based backing/undercoat plasters

 

[RedHerring2]

TM, would that be suitable for a potentially damp wall?

I left it out 'cos I assumed it wouldn't be.

 

[ajrobb]

Have a look at Heritage House. I think it is an interesting site and you might find it reassuring.

 

[karaman]

hallo all,

i have finally decided - redherring2 is right, NO CEMENT. and ajrobb - finally i have read something (heritage house) that makes perfect sense when applied to my place. the plaster i've taken off is all cement no wonder peeling paint, peeling walls, wet bricks.

having waited 6 weeks only to be let down by both damp-proofing guys
all i need now is three weeks of decent weather (huh!), the knack and some cheering up to attain an i-can-do-this attitude.

grateful to all of you for your help, much appreciated.

karaman
the spirit never dies