Breathable product for protecting stonework

[MetManMark]

All
*Hopefully* the three photos I have just taken will appear - when I tried this a couple of years ago I didn't have much luck!

Anyway as you will hopefully see we have exposed stonework at the rear of our house. This was originally done with lime mortar but it has been repointed using cement at some point in the past. We are now starting to remove the pointing in order to repoint using lime. I am not sure what type of stone it is (we live in Mid-Devon) but I am a bit concerned with some of the flaking that you can hopefully see in the photos. The walls are pretty thick so I am not worried structurally but I would rather the stone didn't degrade like this! We think that repointing in lime is a sensible thing to do. Is there something else that we should be doing? We rerendered the front of our house with lime and the stonework at the base we repointed, treated with Beeck fixative and painted using Beeck black breathable paint as sold by Mike Wye. Is there some similar breatheable protection we should be applying to the stonework?

Thanks in advance for your suggestions.
Mark

 

[formerly known as]

delamination of stone will occur when it is 'face bedded' rather than being bedded so the grain of the stone is in compression, and therefore much more durable. You will hopefully see that there is a difference in the way that the stone is used in your walling. Where the builder was working to face up an area with the least amount of material, this would often happen. the OPC based repointing will have accelerated this process. The delamination process is not something which can be fixed - unless individual stones are either renewed, refaced or addressed through 'plastic' repair (not plastic as we know it, but mortar based repair) Just repoint it with a soft lime mortar and certainly don't use any chemical consolidants.

looks like a sandstone to me, but a magnifying glass / eyepiece would help you identify the stone type - rule of thumb is that fine granular and layering indicates a sandstone or an ironstone, although both can have larger inclusions, and that limestone can show shelly deposits ...............

 

[88v8]

..delamination of stone will occur when it is 'face bedded' rather than being bedded..... Where the builder was working to face up an area with the least amount of material, this would often happen...

Yes, even in the good old days, there were botchers.

 

[MatthewC]

..delamination of stone will occur when it is 'face bedded' rather than being bedded..... Where the builder was working to face up an area with the least amount of material, this would often happen...

Yes, even in the good old days, there were botchers.

We've found that on the local church. There's a huge variety of stone used in the basic structure, as though they just found all the cheapest and most easily available stone and mixed it regardless. A disappointing number are wrongly bedded, including some carved hood mouldings on windows. It is very difficult even for an expert to date this sort of stuff but some must be centuries old. Of course, we don't know if it was done by a poor worker, or a good worker who gave the church an option of the cheap job or more expensive proper job. I'd like to think that the repairs currently being undertaken are good quality, but I doubt I will find out in my lifetime!

We have also had a classic: the contractor pointed out the superb quality of the copperwork on the roof on the south aisle where the 50 foot carved parapet wall is being completely replaced. Then we realised that it was probably the same skilled coppersmith who was the idiot who chased a 2" deep groove in the 4" thick wall for the copper upstand of the roof gutter; this is what caused the wall to lean, deteriorate and need replacing.

In answer to the original question, getting rid of the cement pointing should help a lot. Again, we have this on the church - someone thought it would help to smear a one-eighth inch thick layer of "pointing" which just makes a poor situation worse. I'd love to get rid of all that at once!

 

[garnett]

If you are in Mid Devon then you probably know Mike Wye. I suggest you get them to take a look? I have no connection with them other than they provide training for Conservation Officers which covers this issue well.

Garnett