Lime Mortar v Cement Mortar

[weegieavlover]

I am no expert, just a DIYer so apologies if I get any of my terminology wrong.

In my Garden I have 2 small brick sheds that are built inbetween and joined to my house, neighbours party-wall (their outbuilding is on the other side of mine) and back wall. So they are enclosed on 3 sides and are the old coal and ash outbuildings.

I finally sort the leaks they had and want to line with wood, I don't have to but I want to. As the house and buildings are old the mortar is very dusty and wearing away. I plan to chase the mortar out and repoint so that I do not have to worry about the walls after I have lined them with wood.

So I am only mending the walls on the inside and the bricks look like normal bricks, just dating back to about 1890s-ish.

I am not 100% certain but think the mortar used maybe Lime. So I have a few basic questions:

1) Is there a sure way to know if it is or is not Lime?

2) If it is Lime & it being internal walls on brick sheds/outbuildings does it matter greatly if I use Lime or modern Concrete Mortar?

3) If I do need to use Lime Mortar - can you buy it pre-mixed (just add water) like you can normal concrete mortar?

 

[SimoninEaston]

When I moved into my very modest brick-built turn-of-the-last-century town house in central Bristol, I was faced with a similar issue. After I had hacked off the loose plaster from the worst walls, I found very poor brickwork with unfamiliar mortar (OK with my experience, any mortar would have been unfamiliar...) It was grey and crumbly and looked as if it contained a variety of materials including ash, which I gather was quite common back then. Anyway after I asked around, my mortar gurus told me it would have been lime mortar and I enquired about using cement products instead and was advised that I should use lime-based mortar really, but that in practice hardly anyone did use lime-based mortar nowadays, except serious restorationists.
Unabashed I bought a bag of lime, from Travis Perkins, I think, and found it easy mix up & use and so I used it for the small bits of brickwork that I did before having the place re-plastered - I had to enlarge a window aperture and rebuild some brick courses that had collapsed in an upstairs room, above a rotten lintel. Unlike a cement mortar which 'goes off', a bucket of lime mortar was good to use for a couple of days, I recall. Go for, it, I say!
There's is another lime-based product out there which is potentially dangerous - can't remember what's called now but someone here will certainly remind us!
Edit: re-reading some of the lime mortar threads on here, I'd forgotten what a contentious subject it can be - what fun!!
//www.diynot.com/forums/viewtopic.php?t=211546&start=0
Just to reassure you, it does set, it just takes longer doing it. I know, 'cos I went to the trouble of making up samples of mortar with lime in it in various ratios, and I've still got the the lime-only sample, which is very solid.

 

[SimoninEaston]

and get the right sand...
http://www.stastier.co.uk/nhl/guides/sandmort.htm

 

[weegieavlover]

As an owner of an older home I have done repointing before, however I have only just found out about Lime Mortar I know shocking!

My understanding of Lime Mortar is this - it allows porous brickwork like sandstone breathe and release any moisture - is that correct?

If you have a Lime mortar and remove about 25mm for repointing and repoint with cement - what would happen?

I am trying to understand the consequences of using the wrong mortar. I know people might say you could cause e.g. damp, wall to fall down, etc (I am making up a worse case scenario) but how realistic are the problems that might arise likely to become a reality.

Also can you buy bags of Lime Mortar premixed so that all you have to do is add water and mix together? I would be much happier with this solution but could do it manually myself if I had to.

 

[Jackrae]

Googling "pre-mix lime mortar" turned up 29,700 results in less than a second.
So, the answer is YES, premix can be bought in a variety of colours.

 

[weegieavlover]

Googling "pre-mix lime mortar" turned up 29,700 results in less than a second.
So, the answer is YES, premix can be bought in a variety of colours.

Thanks for that

I had already done that but I was struggling to find a e.g. B&Q, Jewson, Build Centre, etc that sold them so I could pick them up (worried about delivery costs). When googling I am struggling to find local to where I live.

 

[Guitar_man]

Lime mortar is softer than cement mortar. It is designed to weaken before the brick or stone. This is probably why old buildings are still standing after hundreds of years, but the mortar is nackered.
There is probably nothing wrong in rebuilding or strengthening small areas with cement. However a large area or a wall if made in stone with no damp course should be rerendered or rebuilt in lime for the reasons you mentioned re breathable. Call the guys at Cornish lime company. Very knowledgeable and helpful in all matters lime. Dont be scared have a go the only pain I've found is you need to be careful re cracking and keeping it damp for the first 24hrs.

 

[weegieavlover]

Lime mortar is softer than cement mortar. It is designed to weaken before the brick or stone. This is probably why old buildings are still standing after hundreds of years, but the mortar is nackered.
There is probably nothing wrong in rebuilding or strengthening small areas with cement. However a large area or a wall if made in stone with no damp course should be rerendered or rebuilt in lime for the reasons you mentioned re breathable. Call the guys at Cornish lime company. Very knowledgeable and helpful in all matters lime. Dont be scared have a go the only pain I've found is you need to be careful re cracking and keeping it damp for the first 24hrs.

Thanks Jimbo.

Each outbuilding has 3.5 walls (one wall has a door, hence the .5) and I plan to strip out all the mortar around all the brickwork to a depth of about 25mm.

What about cement mortar with lime in it?

 

[Guitar_man]

Cement is used to speed up the drying process that's all. If you use NHL 3.5 and a class 28 pointing sand it will go off in 24hrs no problem. You can
mix it in a standard mixer and point just like
Cement. The slower set might be a problem building where you need to allow it so set as you build height. No difference no extra skills required or special tradesperson. The only difference is cost. £10 plus vat per bag for 3.5 lime and 70 plus vat for sand.

 

[cjard]

70 plus vat for sand.

That's a big bag of sand

 

[bobby spray]

Dunno where you are in Glasgow, but 'Masons Mortar' in Govan has all the materials you'll need

 

[weegieavlover]

Dunno where you are in Glasgow, but 'Masons Mortar' in Govan has all the materials you'll need

Thanks Dude.
I am not far from Govan so that will do. I will check them out.

Thanks
Col