Patching Sandstone

[Davmac]

I would appreciate some advice on this one. I think I have read every google article on this and the advice is contradictory.
These are pictures of part of my back garden wall which is soft sandstone, spalling or de-laminating badly and previously damaged with cement mortar. There are deep indentations and some of the stone surface is extremely soft (some OK). I tried one patch with Hansons cement mortar and PVA ...this used a lot of product (as I am small scale and purchase bags and do small mixes) and really this does not look the answer (and I am not sure I am doing the right thing either
Can I ask what others do with this? Is there an optimal way? I am tempted to pull out all the cement (which is likely to cause a bit of damage) and just "point" it but I will be left with a soft spalling surface in places.
Thanks for any advice.

Sandstone2

• Davmac
• 4 Jul 2014
• 1

Sandstone1

• Davmac
• 4 Jul 2014
• 1

 

[jason61c]

The use of cement is the issue, its causing moisture to escape through the sandstone which is effecting its integrity.

Remove the cement and re-point in lime.

 

[stuart45]

Stones that are face bedded instead of on their natural bed will often delaminate.

 

[wessex101]

I would agree with the above but I don't totally buy into the "cement bad lime good" argument.

Difficult to say from the photos but I would strongly suspect that mortar is rock hard, probably a 1:3 mix. That is the main problem.

I would rake it out, probably more like drill/cut/hammer it out as it will be so hard with the unavoidable damage to the stone and repoint in a nice soft 1:1:6 mix (cement:hydrated lime:sand).

As for the damaged stones, not much you can do about that. Sometimes you can take the stone out and turn it around if the back face has been dressed but a fiddly job in a wall like that.

 

[Davmac]

Thanks
I can re point using a lime mix (once I source some)...is there anything I can do to preserve the delaminating surface or indeed fill in some of the indents? The wall is quite uneven now.

 

[jason61c]

I'd point flush and it'll look nice and rustic.

 

[Johnmelad]

Could be worse...

 

[Davmac]

Thanks to you all and for the humour!
I'm going to follow the tips and count my blessings that there is at least some wall left to work with.