Limewashing the house

[Lynn]

I limewashed the back of our house last year as a kind of experiment and it has held up under a Wisconsin USA winter. I have lost the recipe which is a bother because I added a bit of pigment, but I think I can reconstruct those proportions.

My reading has confused me a bit though about additions to the lime and water. Many say add salt solution. Lately a person on this board chimed in to add boiled linseed oil and there was a good discussion about using purified oil so there is not food for microbes. Also I have the bag of hydrated lime from last year and it seems in some quarters that this is hopelessly old and not good for making limewash. Can I salvage it by soaking in water for a week or two (slaking it)? Last year I just mixed the whitewash and applied it. I guess this is not the preferred method of wash preparation. So I have to narrow in on the recipe if you all could provide a consensus.

And then there is the preparation of the stucco. I have read just brush it with a stiff brush, others say wash with TSP-type wash to get the molds and mildews off. It is a cement stucco from the 1920's, but I don't see any paint except limewash. All the layers I have been able to expose and test with vinegar bubble, so I think the whitewash will soak in and seems to have on the part I did last year. Cleaning it will be important, expecially on the north side of the house which is a sight.

How to apply it...wet the walls first, put it on in thin coats. How many coats is a question too. I only did one coat and the patched areas are starting to show through...the wash absorbed differently into old vs. new surface probably. I have read from 3 to 8 coats :shock: and I can't imagine doing that to a house. Even three sounds daunting.

Maybe I should title this exterior limewash 101.

Thanks in advance for your help.

 

[biffvernon]

I wouldn't use last year's left over lime, except as fertilizer for the vegetable garden. There will have been an unprdictable amount of carbonation of the calcium hydroxide in an opened bag. It's cheap enough stuff to get a fresh bag.

 

[L1zzy]

I'm about to start limewashing (weather permitting) I am anticipating 3 coats and I will be putting some linseed oil into the wash (specially purified from Holkham to avoid too much fungal thingies) I'm adding this only because I have a mixture of 'unknown' covering already on the exterior wall as well as areas where I have removed the render and done repairs with Lime Mortar so I need to try to get the wash to 'stick' to all of it if I can.

 

[NT]

Putting salt on houses isnt best practice, it can lead to salt contamination. Old lime is normally fine if its been stored indoors and kept closed. If in doubt, mix a little up, apply, and check after a few days that its adhered. Lime dries fast enough that I wouldnt expect mould to be a problem, lime is also somewhat antibacterial. Storing the lime after soaking improves it, and I would definitely do that, but I dont think thats slaking, unless youve got quicklime there (unlikely). The cleaner the wall is the longer paint will last. Number of coats will become obvious as you go along. It depends on paint thickness, thickness of application and whats being covered. My last wall took 2 coats.

Lime gets more body as it carbonates, there was a small patch where I ran out and just applied one diluted coat made from the bucket sides, and it looked obvious this would need 1 or 2 more coats later. But in fact over a few days it bodied up fine and hasnt needed a repaint.


NT

 

[Lynn]

Thanks for the responses. They led me into a bit of confusion so I searched this site again and found a couple Biff-isms and who doesn't like to quote Biff, so he said about a year ago:

I know this risks upsetting Evelyn, but I've used dry bagged hydrated lime from a builders' merchant and found that it works just fine. Buy from somewhere that looks like it has a quick turnover and as soon as possible empty it into water. I find two 25kg bags fit conveniently into a standard plastic dustbin. Stir well to make sure all the lime is wet and there are no trapped air pockets. Leave to stand for a few days or longer if possible.

My understanding is that this is then slaked lime? or lime putty? or is what NT refers to as quicklime the only way to make slaked lime? Maybe these terms are used differently in UK vs elsewhere, or maybe just imprecisely. I'm trying to follow the discussions but need clarification. Also could I add the pigment to this putty so I have an even color throughout the project, or do I have to mix that just before painting?

Also I loved Biff's picture and want to know where to get one of those brushes...

 

[Gervase]

I'm afraid I use bog standard linseed oil from our local agricultural co-op - it's a lot cheaper than the rarified stuff from Holkham. Limewash is a natural fungicide and bactericide, so mould doesn't really present much of a problem.
I find I do need a fatty additive of some sort to help the limewash stick to the variety of surfaces on my place; ranging from mortar and soft slate through to Preseli bluestone and the odd bit of cement. Tallow is ideal, but it's best added when the lime is slaked when you're making limewash straight from lump lime, which I don't do.
As for coverage; if it's the first time the surface has been limewash, you'll need at least three coats - starting with a 4:1 dilution (roughly) and ending up with a 2:1 - a thicker, creamier top coat. I bung in about a pint(ish) of linseed oil per 20 litres of limewash, mixing the lot with a paddle mixer on an old electric drill.
It's often easier to make it up in a plastic dustbin - 80 litres is enough for a once-over on our place, and if you're making coloured limewash you'll want to make it all at once as you'll never match the colour next time around.

 

[NT]

Lynn:

> My understanding is that this is then slaked lime? or lime putty? or is what NT refers to as quicklime the only way to make slaked lime? Maybe these terms are used differently in UK vs elsewhere, or maybe just imprecisely. I'm trying to follow the discussions but need clarification.

hydrated bagged lime and quicklime are 2 different things. Adding water to quicklime to produce hydrated lime is slaking, adding water to hydrated lime to produce putty is ... making putty.


> Also could I add the pigment to this putty so I have an even color throughout the project, or do I have to mix that just before painting?

why not.


> Also I loved Biff's picture and want to know where to get one of those brushes...

Looks like a duster to me.


NT

 

[middi]

I thought it was a mop !

" mop and lime in a bucket", what is wrong with that, especially with an extendible handle.

 

[Lynn]

Thanks all for the info, as always so helpful. I do need to have a word said about surface prep if there is experience out there.

Also Middi since you are in the thick of it, what recipe are you using, did you make your own putty? are you using pigment? How is it going?

also this from Deep North blog..no idea where this is, but quite fine writing...and on limewashing his place:

Another depressing feature of the entire enterprise was the spiders, which tuck themselves unobtrusively into little nooks during the hours of daylight, but, disturbed by the brush, hurtle out in search of safety only to acquire horrible limewash bootees in the first six inches, at which point you really have to mash them into the stone and hope that they add valuable tallow, since their future has at that point nowhere to go but down.

from: http://www.rereviewed.com/thedeepnorth/?p=18

 

[middi]

We let Gervase answer that question Lynn, I know for a fact that he is well qualified by now to advise on the pros and cons of the options where limewash is concerned.

I just stick to the simple stuff of premixed tubs.

 

[Lynn]

I'm about ready to mix up the limewash and a couple quick questions. I have a 20 gal metal garbage can, I figure I will fill it halfway with water, add 50 lbs of hydrated lime and about a quart of linseed oil to make the putty.

Questions:

Do I add the linseed oil to this putty mix or on a batch basis as I paint?

Am I right to have bought boiled linseed oil? Which I did.

And no one suggested ways to prepare the surface...cleaning with some soap/solvent, just brush?

I hope I can get this done before the weather gets ugly.

Lynn

 

[Lynn]

Ok I'll take a stab at answering my own questions...

I'll add the linseed oil as I mix the batches of limewash

Boiled linseed oil was a spectacular choice, well done Lynn

And just brush off the surface, wet and you are ready to go darling,
so glad I could be of help.

mulitple personalities are a hazard of caring about old buildings

 

[Nemesis]

Lynn - do a google

Limewash

lots of hits!

 

[Lynn]

Lots of hits and mostly conflicting. That's why folks who want help find their way here.

Try to be helpful next time or skip it

 

[Nemesis]

I thought it was helpful. It's always useful to read up even if it's conflicting in my view.

http://www.thelimecentre.co.uk/Library/limewash.pdf

 

[Lynn]

That's a good article. It says raw linseed oil, so I guess I can get that instead.

Now wait for clear weather...

 

[biffvernon]

Raw or boiled - it doesn't make so much difference. I'd use what you've got.

 

[Lynn]

Well I did half of one side of the house and I broke my back. No one said flailing a long handled brush around in circles, back and forth, up the ladder, down was going to break my back.

Word to the wise.

Actually the whole process is going quickly and the color is great and linseed oil does smell pretty good, and I think it will be fine if I can rest up for the next round. Also applying it to old stucco is much easier than new. We had a small entry (mud room we call it) added and they pebble dashed it...doesn't really match the exisiting stucco, but it is stucco, anyway...that stuff is going to take a few coats to cover. The old surface goes very quickly.

Gotta go lay down now....