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Message started by John9999 on May 4th, 2020, 5:24pm

Title: Stone wall
Post by John9999 on May 4th, 2020, 5:24pm

I'm after some help please.

I need to repair a section of garden wall which has collapsed approx 2m long x 1.5m tall. Not done anything like this before but thought I'd give it a go as we're in lock down.

I've read that the following mortar mix is best....what are your thought?

2 (NHL 3.5 Hydrolic lime): 1 cement :6 builders sand :3 sharp sand

Also, is it essential to use Hydrolic Lime or can I use Hydrated? Not sure what the difference is.

Many thanks :)

Title: Re: Stone wall
Post by thescruff on May 4th, 2020, 7:23pm

Assume you mean rough stonewalling.

I've always preferred stone dust about 6-1 cement, other than that see what the guys have to say when they logged in.

Title: Re: Stone wall
Post by John9999 on May 4th, 2020, 8:14pm

Cheers thescruff yes, I think it is rough stonewalling.

Title: Re: Stone wall
Post by woodsmith on May 4th, 2020, 11:16pm

The first thing to note is that with modern cements with added plasticisers there is no need to add lime to a cement based mortar mix. You see lots of information how lime makes mortar breath but that is only if it has no cement in it. As soon as you add cement it negates any benefit from the lime, lime was historically added to cement based mortar to make it more workable.

Sharp sand and cement makes concrete, adding soft sand will make it more workable but unless the stone is very hard its likely to make a harder mortar than the stone, which is not normally a good idea.

Lime mortar has no cement in it, you can buy it ready to mix in bags or you can make your own. And this is made from sharp sand as the lime keeps the mortar permanently flexible.

First thing is to look at what mortar has been used for the wall. If it's softish, coarse, a bit friable and often with flecks of white in it it is almost certainly lime mortar. If it's hard and needs a hammer to break it into powder it's cement.

I've mostly used pre mixed lime mortar as its consistent and you can get it in various colours to match the existing mortar as lime mortar is otherwise very white. If you are going the cement based route I would experiment around a 1:5 mix cement to soft sand and only replace some soft sand for sharp sand if you find the mortar slumps.

Title: Re: Stone wall
Post by thescruff on May 5th, 2020, 8:43pm

I would still go with Stone dust and cement it holds well and fills the irregular gaps with ease.

Title: Re: Stone wall
Post by John9999 on May 5th, 2020, 9:54pm

thescruff and woodsmith many thanks for your advice. It certainly seems to be a minefield of possible mortars to choose from.

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