Lime Mortar & internal pointing.

[unknown]

Hi All, Aparently one of our jobs this weekend is to re-point the chimney breast of our old rubble-stone cottage in Brixham.

Not knowing the score I was packed off to the builders merchant with instructions from my good lady to get some lime mortar.

The man in the builders merchant recommended hydraulic lime (castle 3.5 I Believe) and as we want it to hold things together and the stones are mostly a redish colour as found in south Devon we thought we'd best mix it up to match the colour.

So I have 3 bags of a fine red somethingHead sand and a bag of hydraulic lime.

Can anyone give me a few pointers on mixing and usage given it's for internal pointing.

Cheers Pete

[Fash]

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Unfortunately you probably have the wrong thing of you want to do a good job. Hydraulic lime is not what your original mortar is likely to be made of (assuming the house is fairly old - pre 1900 I'm guessing). It will be a 'lime putty' mix which is non-hydraulic lime. The best bet is to buy your mortar ready mixed from a decent lime supplier, some of whom will match the colour if that's improtant to you. Try a google search on lime putty or lime mortar suppliers and you should come up with some. "cornish lime" and "mike wye" are not too far from you, and anyway everyone delivers for reasonable cost.

The advantage of using a 'proper' lime mortar is that it will look right, have the right texture and not set up problems for the future.

Fash

[unknown]

The Building is rubblestone and constructed early 1700's My good lady has been in touch with Mike Wye and was going to pick some stuff up. The original finished surface was a pinkish haired "plaster" so there wasn't any pointing as such, just a good thick coat of the stuff all over all walls and all stone work. Most of the old stuff was crumbling off the wall/chimney breast and very damp. As we have pulled out the 1950's fire place to reveal the original fire hole we need to point the stone work to keep everything "together"

If we were being historically accurate we'd just need to re-plaster all over and hide everything but we don't want to do that. :¬)

Cheers Pete

[dom]

Good advice. Use hydraulic lime only where you need it (e.g. below damp course, tops of chimneys). Elsewhere use lime putty (comes in sealed buckets, looks like cream cheese) mixed 1 to 3 with sharp sand (not soft builders sand). Be careful about mixing in water - a cupful too much and you have soup (paddle mixers on big power drill in a bucket works well for mixing). Often the putty mixed with damp sand comes out about right with no extra water - you're looking for a mix that you find easy to work with. Try some test bits first.

Th advantages of lime putty over hydraulic lime is that lime putty mortar must "air dry" before it sets. Keep a bucket well sealed (e.g. sealed in binbags) and the mortar can be given a good stir up and be used weeks later. Another useful trick is waiting for it to air dry a bit (after you've applied it to the building), and then brush it down with a stiff brush - easy to produce a finish to blend well with existing work.

[unknown]

Thanks Dom. I'll save the pointing job for another weekend then when we have the right stuff. I guess I'll be able to make use of the hydraulic lime somewhere along the line.

Cheers Pete

[meow2222]

Yes, you want non-hydraulic. You can buy putty but its unnecessarily expensive. Go to any BM and get bagged lime at =A36 a pop, its non- hydraulic. Mix to a paste with water, store it airtight for at least

24 hours, and you've got your putty.

I wouldnt try to overcolour it. Red sand will give you enough colour.

I assume you know it takes days to cure.

NT

[dom]

Agree you can use builders (hydrated) lime and make up your own putty

- but soak for much, much longer than 24 hours to make good putty.

Doesn't need to be airtight container unless longterm storage - just make sure it's well covered with water - I bought a new plastic dustbin for a fiver.

A better compromise might be to buy a tub of lime putty now, and use the homemade putty when the tub runs out

[meow2222]

Long soaks are generally recommended, but not needed. Some folk use it straight out of the bag, and as long as its mixed properly it works fine. Better to mix well and give it a day because it more or less eliminates the risk of small lumps expanding after application. The long soak really is optional.

NT