old habits in Bulgaria

[Guest]

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[kathy]

i live in a village in Bulgaria where the houses are almost all made of cob - its either the main 'brick' for the whole building or its used for the internal walls and its almost always used for morter with real bricks. many of the houses have then been rendered with cement or a mix of cement, sand and lime, or they have been tiled over eg for bathrooms etc. some of these renovations have been in place for 20 - 30 years -the cement on cob I mean, and nothing untoward appears to have happened.
the house i live in was built around 1930, its rendered with cement on top of both cob and brick and its fine. i dont see any of the houses in the village seeming to have any problems but i do understand that putting cement on cob is a big no, no.
so why does everybody in Bulgaria just go ahead and do it and nothing happens?
i cant seem to get a clear answer to this - so hoping someone out there can help

[Steve]

Thank You for your question Kathy.

The main reason why a lot of Bulgarians use/used cement render is because it is cheaper and easier to do because any builder can do it,  the materials are easier to come by, and it doesn't take quite as long to apply.
Many of the houses which have been cement rendered, in the last 20-30 years, will look like there is nothing wrong with them, depending on the weather conditions suffered by the houses, but you can be sure that although no damage is seen to be occuring, there is damage happening below the surface render.
When the time comes that you can see the damage that has been caused by the wrong coating, for example, blown render, cracking cob, and sandy water running down the walls, this is the time where maintenance is an absolute must, and also where the time has come that there may be a risk of exterior walls collapsing etc.
So, when you think that everybody in Bulgaria uses cement render and nothing happens, it does happen, and it is happening, it is just that the eye can't see evidence of this yet, unless you take some of the render off and look behind.
The cost of re-rendering properly, is far cheaper than the cost of rebuilding an exterior wall, and rendering when the wall finally falls down.

Steve

[kathy]

i'm still not convinced - the reasons that people here use cement is not as simple as you suggest but thats not the issue - the weather here is drier than you probably imagine for Europe  and there is never, ever wind with rain. all of the rooves overlap the houses and the walls of the houses never get wet unless there is a hole in the roof. so if the cob bricks are dry - and i mean really really dry and then cement render goes on and there is no leak from the roof, what is going to cause the damage?
the bricks on my barn are about 50 years old - there is not one drop of moisture in them, they've dried out in loads of summers of around 45 degrees, they never get wet and they never get damp - it is never damp here - so if i put a cement render on them, what do you think is going to happen? if your answer is anyway related to moister, where is the moisture coming from?
I'm not necessarily defending cement render, nor am i necessarily going to use it, but, as the Buddha says, beleive nothing....

[Kevin]

I can suggest two reasons, one is that the render has not been on long enough as yet to show any signs on the outside of damage, but can guarantee that inside the cob walls is damp as the moisture that is inherant in cob has no means of escape. This will manifest itself firstly with damp on interior walls at ground level and will then move towards the outside eventually cracking the mortar and causng it to hollow and in extreme cases if not diagnosed to collapse.
The only other explanation possible is that with your very hot summers the cob gets to dry out thoroughly, and so through the winter it gets damp again but not as severly as in the UK where we have lots of rain.
But I can guarantee you that the cob behind the render will deteriorate.
You seem to know cement is a no no on cob I wondered if you were also aware that ordinary plasters should not be used either, they should be lime inside and out with limewash and not ordinary masonry paints.
Hope that answers your question.

[joskin69]

Zdrasti! I have been thinking a lot about this moisture thing and yes, having been in Bulgaria in Dec when it's 3 foot deep in snow, I really felt a lack of dampness, nothing like the UK, however moisture is ever present, from our bodies, breathing & sweating, we create moisture when we cook and then there is the general humidity of the climate.
I had a look around and for Varna: Humidity is Min: 68 percent Max: 85 percent
                                      Sophia:              Min: 61 percent Max: 85 percent
Would measuring the humidity help?
I think I'm going to play it safe and go for the full traditional cob experience anyway. There are other reasons for this too, it's cheap, materials are found locally which helps keep my carbon footprint in check and the thermogenic properties are excellent ( keeping the house warm in winter and cool in summer)
and the process of building with cob is creative, one can shape the cob freely and make for a more organic and natural finish, I am not a big fan of square boxes and I love rounded flowing alcoves, undulating seating areas and niches for nick nacks.
It's an interesting subject and of course, methods vary from place to place. I am wary though of those obsessed with cement and concrete when all we need we have under our noses.
Long live cob!
Regards
Jo

[Paul]

Thank You Jo,

That's a very good and informative post, and we wish you well in your cob adventures!

Paul