Which lime mortar?

[Kathy]

Hello,
My old boiler died and I had a new one installed on Monday. The fitters removed the 20cm square flue which has left a huge whole in a foot thick wall. I have found the 2" handmade period bricks I need to fill it but I have a question about the lime mortar. I am not far from a big supplier so can collect in person but there seem to be several grades. Could someone advise which one would be suitable for this project? I only need a small quantity.

 

[stuart45]

Is it face brickwork?

 

[Glenn586]

The higher the number the stronger the mortar, 5 being the strongest. If you are just patching up I would be more concerned about a good colour match otherwise it will bother you every time you walk past. In all reality even the weakest mortar won't effect the overall structural integrity. If you were re-building the whole wall it would be a different story.

 

[Lacan07]

You can't go wrong with an NHL2

 

[Kathy]

Old flue, new flue - what a difference!
Stuart - yes it is just the facing (will use normal bricks for the infill) - not a big project like some of the ones I read about on this site!

Lacan- I found I can buy a tub of ready mixed non-hydraulic lime mortar. Will that be OK? I don't need much and I doubt the brickie has ever worked with lime so trying to keep it simple. If kept airtight it could be used future repairs which might come in handy. There are three grades so going for coarse with grit which is what mine looks like. Sound OK?

Glenn - agree the wrong colour would really annoy. This ready mix only comes in a neutral/off white but is more or less what I have so should work (she hopes).

For this job does brickie have to do anything other than actually re-point? I read you have to keep everything moist but maybe that's for larger projects?

Thanks all for your advice.

 

[Zebra]

Yes, ready mixed will be OK. It will be putty-based rather than NHL, since you can't buy NHL premixed (it just goes off in the bucket), but a putty-based mix will be the easiest to use so if your brickie is not an expert then I think that's a very good idea. The colour may look weird at first but it will weather down and over time blend in and look less yellow.

Have a look at a couple of YouTube videos for pointing with lime mortar. Yes you have to moisten the bricks first and then once the pointing is done, keep it moist as it takes a very long time to harden, unlike cement, so spraying with water and covering with some sort of cloth is the way to go.

 

[Lacan07]

Lacan- I found I can buy a tub of ready mixed non-hydraulic lime mortar. Will that be OK? I don't need much and I doubt the brickie has ever worked with lime so trying to keep it simple. If kept airtight it could be used future repairs which might come in handy. There are three grades so going for coarse with grit which is what mine looks like. Sound OK?

I think you mean 'non-hydrated' lime. These titles can be confusing as NHL stands for 'Natural Hydraulic Lime', which basically just means it can set under water.

Its not really the right time of year to be using non-hydrated lime as it takes a good 3 months to cure and needs to be protected form extreme cold. NHL mortar is a far less fussier lime to use and more structural (harder) which can be beneficial when patching or filling service holes, etc, but then again you shouldn't really been using that in the middle of winter either.

If the gap to fill isn't too big you can just use expandable foam or similar, or just stuff the void with plastic bags and wait until spring to finish with lime.

 

[Zebra]

I disagree with your interpretation, Lacan, I think the op meant non-hydraulic as in not NHL. Although I agree that it's not really the right time of year to be using either right now.

 

[Lacan07]

I disagree with your interpretation, Lacan, I think the op meant non-hydraulic as in not NHL. Although I agree that it's not really the right time of year to be using either right now.

Yes, reading it back again it does seem rather open to ambiguity, perhaps Kathy will return to clarify