Pointing/repairing stone wall - what mortar to use?

elliot341

Hello everyone,

Along the boundary of my house there is a retaining wall which stops my house from falling down into the neighbours. This wall is effectively a dry stone wall (not sandstone) which has been pointed/set with cement/similar mortar but in a few places (this wall is maybe 8 m long, with 1 m high on my side and 2.5m high or so on neighbours side) some of the stones have come loose.

From reading online it appears that all stone work should be pointed with lime mortar of some sort, not what it appears to have been pointed with currently.

My question is as I have a number of areas I want to repair (possibly 5% max of the wall) should I endeavor to learn how to use lime mortar (and look into where locally i can find it - I live near Bolton) to repair the wall with, or as the majority of the wall seems sound with the current pointing should I repair with a standard cement mix to get the wall back in a decent shape as its more important to get the retaining wall secure and in good repair as soon as possible and eliminate any further possible risk?

any tips or advice appreciated, thanks

bobhawke

The reason lime mortar is used is because it gives way before the stone does. Cement based mortar is too strong and the stone fails instead of the mortar. Any conservation work has to be done with lime mortar. Lime mortar is more expensive and more difficult to work with.

elliot341

I understand why it is used, Ive read into it a bit, is it worth repairing small areas with it if the majority of wall is pointed with cement? I don't have the time or money to rake out the whole wall and repoint with lime, so what is more important ensuring the integrity of the wall (like i say the majority of the wall is sound with the current pointing) or repairing the wall true to its materials? I appreciate your input :j

DVardysShadow

If it is a drystone retaining wall, then pointing may be counterproductive. A drystone wall is intended to retain soil but let water flow freely. Build up of water may be the reason for the pointing failing and stones coming loose.

elliot341

Apparently (speaking to other people in the village) the wall is originally one of the oldest in the village, but as of the 70's the extension built on my house takes it to within 5 feet or so of the wall, so I imagine that to ensure the structural integrity of the wall it has probably been rebuilt and cemented. It is an interesting point regarding the water though. hmmmm. Thanks

bobhawke

If the majority of the wall is pointed with cement then no it isn't worth it, unless you rake out all the old mortar.
If it is a retaining wall then it should have weep holes in it to let water out. One of the main reasons retaining walls fail is water building up behind them.