more limewash questions

[charlie-ia]

" LIMEWASH

Posted By: DAVID KAMINSKI
Date: 10/5/2006 at 11:09:48

IS IT POSSIBLE TO LIMEWASH A CEMENT RENDERED BUILDING? "

Mr Kaminski,(&co.)
Im interested to know if you did eventually limewash your concrete, as we're in the process of adopting a poor unloved house, again with cement render.

The most important repairs do not include painting, but it is such a sad dingy colour (with a liberal coating of algae) a quick lick of white would be nice, though we're quite sure the render will be removed later (its rather patchy to say the least!)

Does the limewash stick ok without thorough preparation?
What's the minimum number of layers you can get away with?
Is there a special recipe to give good quick coverage?

We thought it would be good practice, if nothing else!

Also, how do you tell if the cement is origional?
The house is reputed to be around 1900, two stories and stonebuilt

Regards to you all,
Charlie

 

[NT]

I had no problems painting concrete using diluted lime putty.

2 or 3 coats was fine IME. Subsequent coats were put on very quickly after the first - if done this way it is important to be gentle with the brush and not overbrush, in order to avoid the prvious coat redissolving.


NT

 

[charlie-ia]

thanks NT.
am looking forward to getting started!

Should stone work never be rendered with concrete? Been dutifully reading the past messages, and its clear everyone loves lime.

this house isnt that old, but im thinking if its allways been concrete, then it should be replaced with the same. is this correct reasoning?

 

[MdB]

I'm new to all this lime lark but I've been reading up....

The following is the way I see it currently, if someone can correct me if I am wrong please.


"Old" construction, be it stone or brick, often had poor or no foundations and used lime as a mortar. Over time, the construction tends to move as it expands and contracts with temperature and moisture content. The lime mortar has a certain amount of flexibility and can self heal so the wall can cope well with these movements. Many of the materials used in the construction are often porous so water can penetrate the structure. It is therefore important that breathable finishes are used to allow the water content to evaporate over time.

"New" construction, be it brick or block, has good foundations and uses cement as a mortar. None of the structure is flexible and (should) keep a water tight finish. As water can't get in, there is no need for breathable finishes.

The problem comes when "new" methods are used to repair / improve "old" methods. If a cement render is added to an "old" wall, it will in the short term stop the wall from breathing causing a build up of moisture within the wall which will cause damp patches and generally degrade the wall. In the longer term, the wall will move and cause the cement to crack. This will allow in additional mositure but will not allow it back out again.

In your case, is the stone porous? and is lime mortar used in its construction? If either answer is yes then I would have thought a lime finish would be better so as to allow the moisture within the wall to escape. If however, you have a non porous stone with a cement mortar then it "should" be difficult for water to enter and hence a cement render may be appropriate. However, as it appears to have failed in the past, it will probably fail again so it suggests that it is not a good solution.

 

[charlie-ia]

The house appears to be limestone, so clearly porous. thanks, youve summed it up nicely. The house isnt technically ours yet, so im using the time to read up on as much as i can

"The problem comes when "new" methods are used to repair / improve "old" methods. .[/quote]

what happens the other way round? using old methods to repair a "newish" house?

 

[NT]

thanks NT.
am looking forward to getting started!

Should stone work never be rendered with concrete? Been dutifully reading the past messages, and its clear everyone loves lime.

this house isnt that old, but im thinking if its allways been concrete, then it should be replaced with the same. is this correct reasoning?

If you want to damage the stone when the render eventually fails, then yes cement is the way to go. Cement pulls part of the stone off when it comes away. There are other problems with cement on old buildings too. Lime is recommended becuase it doesnt cause the problems that cement render does.


NT

 

[Anne]

"Old" construction, be it stone or brick often had poor or no foundations

This is a very general statement and varied greatly. If you were looking at a wealthy stone or half timbered house from the 15th century your foundations could be up to 4 feet either side of the wall, on a non-defended site but if you had a peasent house built in a day you wouldn't have much foundations as they were only allowed one day to build it and had to have smoke coming out of the chimney by night fall. This type of practice carried on for hundreds of years, it was down to finances as to how good your foundations where as well as your builders knowledge.

On cement render, I'm curious to get opinons on if it's best to leave well enough alone or if it's worth trying to take it off. Horrible horrible stuff that it is won't come off and won't stay on an old building without massive cracks. I'm refering to internal walls which have been plastered with a cement based render and I'm not sure if I should try and remove it as I don't want to hurt the wall to much.

 

[Moreteyne]

Anne
Dont you find the non porous effect causing condensation this time of year ?
Moreteyne

 

[Gervase]

My own view is that, wherever possible, one should remove cement render. That's an ideal, however, and reality does intervene.
Some walls are in grave risk of damage if the render is removed without huge care - particularly irregular stone walls with a mud bond. On such walls the cement is far stronger than the wall itself, and if the 'renderer' has raked out the earth joints beforehand it's very hard to remove the cement without dislodging the stonework.
You can also have problems with old laminar stone, like slate or some limestones, where the rock is bedded in layers which cleave easily. If the stone has weathered badly before the render was applied, the decay and delamination can be such that the stone disintegrates when you remove the cement.
On such a wall I'd say that unless you have a lot of money to pay for very painstaking work, leave well alone. When cracks appear and the cement starts failing, patch with breathable materials, but don't force the render off.
Internal walls are often more problematic than external, because outside faces were built strong and square to resist the elements, whereas the inside faces were often far more 'raggy' because they were to be meant to be plastered.