Mortar for Hornton Stone????

[tom.harrigan]

Hi

According to my local quarry, the local mortar mix for building in hornton stone is 1:1:8, with the "8" being "yellow" sand (whatever that is - I presume they mean soft builders sand?).

According to a lime expert that I met at the Homebuilding and Renovation show, whose products are sold through my local quarry, I should under no circumstances use soft sand or cement, but rather a very sharp sand and his expensive lime products. Mix 1:3 (or purchased ready mixed).

The old chap who built the 1970s extension to my 1790s house said he used a 1:10 mix, but could not remember what the "1" was. He seems to have used an extremely fine sand, so fine that when you crush a sample of mortar in your hand (it is that soft), if there is a whisper of wind, half goes up in the air.

I have been using a 1:1:6 mix with the "6" being 2 soft soft, and 4 sharp concreting sand. I'm a total novice, and just can't get soft sand alone to support the stones (they have a flat face hut the tops and bottoms aren't), and I find pure sharp sand difficult to work with. I have been doing mostly infill, repair and installing oak lintels at the back of the house.

I now have about 20m2 of (random coursed) stone wall to build, and about 25m2 of random stone wall to point, which are next to each other. The repointing is on the old part of the house, and I'd prefer not to use cement there. The old walls are stone+mud, with traces of all sorts of pointing. Any advice would be much appreciated!

T.

[Fash]

The expert isn't necessarily right. It really depends on what was used when the house was built. My 1750's house has no trace of "sharp sand" in the lime-mortar, the best match I've found is top coat lime plaster. You should try and get a match to what's already there where you're working on existing masonry, whether that's lot's of sharps or none.

To be honest, whilst lime 'stuff' is expensive compared to sand and cement it's not really breaking the bank, certainly when compared to labour costs. Ready mixed lime should be ~=A3150/tonne ready mixed. It's definitely best to buy it ready mixed as then all you need to do is knock-it up a bit before use and it keeps pretty much indefinitely if airtight. Prices vary considerably so its worth a) looking around and b) trying to ascertain if it's a good match.

Regarding the new wall, if you're going to the trouble of using lime for your repointing then I would use it for the new wall as well. It's not really any harder to work with, it doesn't go off as fast as cement does, which means you have time on your side, useful if you're not an experienced stone layer.

Bite the bullet, get your wallet out and do it with lime (but not necessarily from your expert). You can tell everyone that you did it to reduce your carbon footprint and score extra greenie points as well!

Fash

[meow2222]

Any solid mix will hold the wall up, the differences are in long term damage to the stone and in damp handling. Cement mortars, unless excessively weak, pull the corners off stonework when they eventually let go. Lime mortars dont. Cement mixes evaporate little from the mortar, wheras lime evaporates water well. This means salt deposition occurs primarily on the lime, avoiding damage to the more valuable stone.

1:3 to 1:2 lime to sand is the best mix.

For some reason there's a lot of overpriced lime putty about. Get bagged lime for =A36 a time and turn it into putty by adding water. Either mix well and use right away or dont mix at all and give it a few weeks to make sure the water's soaked all through. The ilme to use is standard hydrated non-hdraulic lime.

For a more PP oriented forum, try

[tom.harrigan]

Unfortunately the only original "mortar" left is the dusty soil between the stone. There are some traces of lime mortar pointing in the roof space, and generations of crappy cement pointing. My house isn't actually from the 1790s, I used poetic license as the extension _is_from the 1970s. It's supposedly from 17??, but there are no records.

My problem is partly what to match to. I can believe most of the new and restoration work in the village is 1:1:8. Most of the pointing looks sandy in colour rather than grey or white. There really is nothing I want to match on my house, certainly not the 1:10 at the back or the cement pointing at the front. Lime mortars go pretty white, which I'm afraid will make my house look weird. The random stonework of the front (the old part) has some pretty thick joints.

I suppose I could reduce my carbon footprint even more if I source my lime from France - electric kiln 80% nuclear!

T

[The Natural Philosopher]

I got a very good look and feel using sharp sand, white cement and lime. About 1:1:5 or 6.

[The Natural Philosopher]

What he means is that thebricks orstimework faisl before teh cement.

Cement doesn;t *pull& anything off anything: However with porous brickwork and far less porous cement mortar, you end up trapping water in the porous stuff which then is subject to frost attack.

Simply using a weaker mix prevents that. Air gaps between the sand grains mean its porous.

Cement mixes evaporate little from the

Yup. Its about the same price as white cement.

one shovel of whitee cement, one shovel of lime and 6 shovels of sand..

[Fash]

If you want it greyish then buy the lime from cornish lime since that's the colour they have. Don't buy lime from the builders merchant to make lime mortar though, it's rubbish. It's partly calcified already and just won't produce a satisfactory lime mortar. It's fine if you want to add it to a cement mix to plasticise it, but is that really what you want to do.

You can potentially get more advice from the forum at

.uk but don't use their list of suppliers, because only the expensive suppliers advertise there.

This heritage stuff is a matter of balance, if you have an old house, then why use cement when lime mortar is fairly readily available. However, don't touch a 'heritage' builder with a bargepole because he'll want one of each kind of limb to get out of bed in the morning.

I've had quite a lot of structural work done on this house, mostly in lime, and just employed a local brickie, but I supplied the materials since his idea of lime mortar was similar to most peoples on this forum, i.e. make up cement mortar and chuck a spade of hydrated lime into it. The work came out absolutely fine once I'd reassured him a few times that I really wasn't expecting it to set fully hard within the hour (or week!).

Fash