Solid wall lime mortar- urgent query please, sorry.

[mh12]

Hello everyone.
Apologies have not been active on the forum as lost in the work at the moment. Situation to date:
Rear single storey cavity extension will be attached to traditional solid wall Victorian (9 inch thick non cavity wall building) off course Victorian wall has lime mortar, top part of wall OK bottom part not OK.

Height of facing bricks of extension approx 2.7m to eaves level as measured from DPC.

Most of the bricks of the adjoining wall old solid wall is in poor state , luckily only the bottom section of the wall (the facing single layer of bricks- some spalled, some with paints etc) which run continously with the extension wall .

These spalled facing bricks are between the engineers and the 2.7 m height as measured from the engineers.

I am planning to take a section of old wall out BUT only the outer leaf external bricks due to above reasons. The internal leaf of old wall stays as is.

So section of old wall about 3.2 m length and 2.7m height to be removed, getting acro and strong bouys put in today, I m going to remove bricks today and hopefully brickie will start work by tomorrow on this section or latest by Monday.

Question:
1) Do I use Non Hydraulic Lime/Lime putty or NHL 3.5 as mortar joints for the outer leaf Victorian solid wall replacement?

2) With NHL will I need to get sharp sand and yellow building sand ? - already have yellow sand, thinking of ordering1 tonne of sharp sand if its required. IS that sufficient?

3) How about Non Hydraulic Lime/Lime putty do I need any other ingredients to make mortar mix up e.g sharp sand, plastering sand etc

4) Does plastering sand come into the mix as well for making lime mortar or will sharp sand be sufficient?

Thank you in advance , off to the site as gettting acro set up and removing old bricks

I'm based in Birmingham. Can get NHL 3.5 and the sands easily from local merchants. So EHS Smith or Tippers. Both supply Heidelberg NHL 3.5

https://www.ehsmith.co.uk/heidelberg-materials-25kg-natural-hydraulic-lime-white-3-5-00060406

Done calcs will need about 20 bags I think for 10mm mortar joints for 73mm height facing bricks for the replacement area 3.2m by 2.7m

Please correct me if I'm wrong with calcs or any other info
Many thanks

 

[a twig]

With either putty or NHL a 1 lime : 1 sharp sand : 2 builders sand is my go to mix for brickwork or stone work. So just make sure you have at least half as much sharp sand as you do builders.

Don’t use plastering sand for mortar

I suspect others may disagree with me here but as long as your bricks are reasonably hard (not soft reds or similar) I’d go with NHL3.5 otherwise NHL2.

Having done a small amount of brickwork using a putty based mortar in the past you can’t do many courses in a week due to the slow set times so I’d avoid that if possible.

Hope that helps, good luck!

 

[Kearn]

Remember when you’re calculating volume of sand, the ratio is by volume, not by weight. You will need more sand than you think.

If you speak to any of the standard suppliers for lime etc, they can calculate the quantities required for you. My go to is Eden Hotlime.

Ratios depend on your sand aggregate really, I’ve been using NHL2 StA 1:3 (2 builders, 1 grit up to 2mm). But then my joints were smaller and increasing the grit wasn’t good for bedding, but for pointing it was just 3 grit for appearance. Therefore we laid and then pointed, rather than doing in one hit.

I can’t see NHL being terrible in your setup, although ideally I’d get St Astier and use 2 not a standard merchants 3.5 - that way there’s more trust in the actual set hardness not being excessive.

 

[mh12]

With either putty or NHL a 1 lime : 1 sharp sand : 2 builders sand is my go to mix for brickwork or stone work. So just make sure you have at least half as much sharp sand as you do builders.

Don’t use plastering sand for mortar

I suspect others may disagree with me here but as long as your bricks are reasonably hard (not soft reds or similar) I’d go with NHL3.5 otherwise NHL2.

Having done a small amount of brickwork using a putty based mortar in the past you can’t do many courses in a week due to the slow set times so I’d avoid that if possible.

Hope that helps, good luck!

Many many thanks twig and Kearn

The bricks I have chosen are classic weathered orange. Please see spec below. Based on this information is nhl 3.5 an option or is it better to use nhl .

The mortar joint thickness will be 13 mm to match some of the old bricks which are 76 mm height with the usual 10 mm joints.

What is the difference between standard nhl 2 and nhl 2 st austier. Many many thanks.

I have decided to use either 2 or 3.5 following your guidance.

 

[stuart45]

You say you've got a brickie starting work. Hasn't he had any input into what mix is required?

 

[Kearn]

StA is considered to be the least bad of NHLs. More free lime, more consistency and truer to the number stated. Many other bags will be way over the stated harness. It’s a minimum not an absolute.

For hard stone, in an exposed location, 3.5, but here 2 is hard enough.