Render removal & repair to flint & cob walls

[RChurch]

Morning all,

In short I have begun to remove the cracking render from 2 external walls. There used to be a chimney many years ago on this end of the house and a flower bed up against the external wall (I removed this as soon as we moved in!)
The cracking render is a mix of lime (hooray!) but it has been heavily patched with cement, sand & cement to fill the cracks, horrible pink plaster etc etc. All of which has been painted with modern paints not limewash.I could smell the damp when I began to remove the existing render. Trouble is due to its strength it pulls varying amounts of the wall with it when remove even when done very slowly and carefully.
We have some damp showing internally on the lower walls and on the remaining hearth stone.
My biggest fear are the cracks in the cob that I uncovered (some 3-4 inches deep and wide) thus I have taken an extended tea break whilst I seek futher advice. I am guessing that with the wrong render and paint the wall is trying to breath but forcing any moisture to the internal walls and thus showing as damp internally because it cannot escape through the external wall?

Slate tiles added to the base of the wall also appear an odd addition - unsure how long they have been in situ for, should I remove or leave well alone? They have been put all the way around the house.

Really I would like to know -

1. Should I hack off both walls completely including the slate tiles, fill and limewash until next Spring?
2. Hack off and repair cracks as I go then limewash and re render over the coming weeks?

I have done some reserach around use of cob tiles and stitching the wall but unsure if the wall in question requires this or more or indeed less - if less how should the cracks be repaired or filled?

The internal wall at 1st floor level has been fully re lime plastered as we discovered exposed lathes and cob there also when doing the internal works.

Any help or advice on materials, techniques etc would be gratefully received.
I am off to the lime centre later today ((hxxp: www. thelimecentre. co. uk/) to get their advice and begin to look at materials.
(Tried to add photos but thier appears to be a ltd file size on this forum?)
Regards and thanks
Churchy

 

[Aeroguide]

Hello Churchy,

I was at the Devon County Fayre last week end. Came across these people:

http://www.mikewye.co.uk/

As I have a cob property I was interested to see what they were about. Very, very knowledgeable. They do courses, supplies and information is only a call away.

 

[christianb]

Hi Churchy,

Obviously, it's difficult to make even the simplest of appraisals without some images to go by. But a couple of initial thoughts...

First, you need to get some idea of what is causing (or more likely caused) to cracks to form. A simple rule of thumb is to look directly below the highest point of the crack as this is where the rotation (if that's what it is) will be most likely located.

I have to assume that as there have been attempts to cover the offending problems that these are old structural problems rather than recent. Still, one solution is to bed in stainless steel bars (with a barley-twist shape), or go the whole hog and stitch with cob blocks. SPAB might be able to help point you in the direction of a structural engineer with knowledge of the material in your area.

And, yes, the most likely cause of the damp is the external covering preventing eveporation.

C.

 

[Aeroguide]

BTW, go here if you want to post images to forums:

http://photobucket.com/

One of many.

 

[MdB]

Hi Churchy,

Welcome to the forum.

I would second the recommendation on going on a course with someone like Mike Wye, I went on their lime course - well worth it, you will learn a lot. Various people do cob courses I believe.

I know little about cob but from what I've read and heard about, it is a great material when dry but can collapse when wet. There are various horror stories about cob walls falling down when cement render is removed as it is so wet inside. I would hold off doing much more work until you have had comment from a better expert than I. Pictures would really help others to comment better.

 

[RChurch]

Thanks all for the prompt replies!

Photo link below -

http://s930.photobucket.com/albums/ad141/churchy05/Long%20Cottage/?albumview=slideshow

Would love to attend a course as I am off work at the mo so another reason for me beginning to sort these walls however with weather and time of year I guess I am up against it time wise with respect to rendering etc

I have completed alot of reading around the subject and am a fairly practical so want to get my hands dirty really - the only bit I am not comfortable with is the cracking that I discovered - the internal walls the other side of those in question have been re lime plastered and repaired accordingly.

I am awaiting quotes from 2 companies that have been to visit and am also seeking advice from the Lime Centre near Winchester however clearly I do not want to toil away and then have to call in experts next year to redo it!!!!!
There are however a few guys in the village who have tackled similar projects so I do have local help on hand.

cheers
Churchy

 

[MdB]

In my very inexpert opinion (never trust anyone that you have just met on the internet), that crack isn't too much to worry about. It has likely been there for a long time and attempts to try and stitch it together are likely to cause more damage than they will cure. I doubt also that any fix would increase the strength of the wall either. Cob has poor tensile strength so if the wall moves again it will just crack again, fix or no fix.

I would render in lime and then monitor.

(but get a proper experts opinion as well)

A guess about the slates might be that they are there to protect the wall from rain splash.

(oh and well done for understanding the need to remove the cement and replacing with lime. It sounds like you are trying to do the right thing for the house)

 

[chuckey]

The slates on one side(?) are to protect the wall from the raised earth of the flower bed.
Frank

 

[RChurch]

Hi all,

Well progress made this weekend - spent a very useful hour or so at the Lime Centre near Winchester being educated on Friday!

Slates removed and there were not only 1 but 3 layers in places all nicely stuck on with sand and cement!!! Seemingly a very poor form of damp- proofing however the cob and flint was actually dripping places! The house seemed to breathe a sign of relief and continues to dry out as I type!

None the less alot of pointing required within the flint work and confirmed that a chimney used to exist at that end of the house because the wall has been infilled with brick where the flue and chimney breast ran externally - these bricks were also sodden and dripping soot!

Now just the rest of the rendering to remove - oh joy - cob cracks to repair and then a re-render.

Top tip for loose cob and crumbling walls as advised on Friday is a weak mix of lime and water flicked from a long hair brush onto the wall - messy but a quick and effective way to stabilise any loose crumb until further repairs can be completed.

Will post further photos as I go and keep you updated - if anyone is interested!!!!!

 

[kevmiles1]

Sounds like you are doing the right thing and are going to carry out the work yourself. My only concern is that (with all due respect) a novice carry out the stripping of a cob wall and the rendering in lime, is not something I would recommend.
If your cob walls are not damp and are in excellent condition then you my get away with, but if they are not (which happens most of the time) and you also do not apply the lime in the correct manor then you may just be hiding problems that you do not know how to deal with temporarily or at worst you could have a collapse whilst stripping.
Would strongly recommend a specialist do the hacking off and then re rendering