Correct Lime Mortar mix!!!!??? type of sand?

[drummer_boy]

Hello everyone?

Hope you're all well?

i have some brickwork to repair & repoint, but what type of Lime mortar mix do i need?

i don't want to buy it ready mixed as there is rather alot to do?

So, what type of lime do i need to use (is there a type i should stay away from? if so, what one?)

What is the correct mix (for internal use & external, if different?)

Do i need a special type of sand?..............again, what type?

Do i need to use anything else like hair?..............as im contemplating a hair cut right now anyway?!!


All the best & thanks in advance!

Chris.................aka.........drummer_boy, yep i really do play the drums!!!

 

[NT]

quote drummer_boy

> i have some brickwork to repair & repoint, but what type of Lime mortar mix do i need?

normally 3:1 sand to lime putty.


> i don't want to buy it ready mixed as there is rather alot to do?
>
> So, what type of lime do i need to use (is there a type i should stay
> away from? if so, what one?)

the usual bagged hydrated lime found in any BM and most sheds is whats needed, £6 a big heavy bag.


> What is the correct mix (for internal use & external, if different?)

3:1


> Do i need a special type of sand?..............again, what type?

no, tho sharp sand is gnerally prefered.

> Do i need to use anything else like hair?..............as im contemplating a hair cut right now anyway?!!

no


NT

 

[drummer_boy]

Thanks very much for a speedy reply!

3 parts sand & 1 part lime putty?

I had no idea it there was that much sand in a mortar mix!? (it always looks so white, you'd think it was ALL lime!?)

So, we're talking volume here? e.i. one bucket of a lime putty to 3 buckets of sand?

Thanks, Chris.

 

[drummer_boy]

please excuse my poor grammar..............it's late & i'm tired!? lol

Chris...........wgeohnehoebds

 

[worms]

I think NT means bagged dry hydrated lime - much cheaper than lime putty. The dry lime can be mixed with the sand and then wetted rather than starting with putty.

If you want to use putty, then tip the bag of lime into a plastic bin, fill the bin with water, give it a mix and leave it for a week or so. The lime will settle out and form a putty with a layer of fluid above it.

It is not recommended to do outside pointing when there is any risk of frost, so you better get a move on if it is going to be done this year!

 

[biffvernon]

3 parts sand & 1 part lime putty?

That's right - the idea is that the lime fills the spaces between the sand grains. Three bucket-fulls of sand takes up the same space as three bucket-fulls of sand plus one bucket-full of lime.

On a bigger scale a brick wall is made of bricks and mortar. The mortar fills the spaces between the bricks. Same idea really.

 

[drummer_boy]

Thanks guys, sound advice

i'll do a small (mug sized) mix 1st, i just cant imagine it looking the same as the existing lime mortar!?.......................the mortar we have is SOoooo white!!!?

So i need to leave the lime for a whole week to form a putty? or will 24/48 hours do? & do i need to stir it in this time?

Once mixed & used, how long will it take for the mortar to go off properly, for us to plaster over the internal wall?

Thanks in advance, Chris.

 

[thiambal]

Should not be a problem getting the colour - the ready mixed mortar I have been using has tried almost pure white - bit of a bugger really as the exisitng motar is a yellowie colour

Still, Biff's suggestion of a teabag has taken the edge off it a little

 

[biffvernon]

So i need to leave the lime for a whole week to form a putty? or will 24/48 hours do?

No. That's what some folk (with time on their hands?) recommend but it works just fine if you use it immediately.

Once mixed & used, how long will it take for the mortar to go off properly

Lime mortar gradually hardens over days, weeks, months and longer but you can plaster over it, using lime plaster as soon as it is firm - a day or two.

The colour is partly dependant on the sand. If you don't want it too white add some earth to the mortar. (I don't think it was me that suggested teabags - you'd need to be a very heavy teadrinker to have much effect.) Brushing the mortar lightly to reveal the sand grains, not coated in lime, makes the pointing lines less bright white. It all fades to brown eventually.

 

[thiambal]

Quite right Biff, I have just looked back and it was Nemisis - sorry Nemisis!

 

[drummer_boy]

Hi thanks again! my......you are a kind lot!

I'll be attempting this over the next week............but just so you know, i actually want the mortar to come out really white as it will match the existing mortar!

If anyone knows anything about the correct mix for repairing plaster of paris cornice please could they respond to my other post? just look for drummer_boy..........i posted it a day ago, so it should still be on the 1st page on the forum!?

Thanks, Chris.

 

[worms]

I'm a wee bit confused here. You want the pointing mortar to be white enough to match the rest, but you also want to know how soon you can plaster over it?

With the very white pointing this may be a different sort of pointing that others on here can help with - I seem to remember others posting on how to make up the chalky-looking final grouting mix that is used on some properties. Was it silver sand and lime and a higher proportion of lime in the mix?

 

[drummer_boy]

Hi Worms, yep that's a fair point...........no pun intended, honest!

i just want to make sure we are repairing the building sympathetically.........& whilst the internal wall will be plastered the external wall will be left exposed as, of course, it should be.

The mortar through & through is very white (in places, some dork has at some stage repointed areas with the dreaded cement!) we mearly want to repair authentically.

besides, i just like to have as many facts as possible before i try my hand at something!

Cheers, Chris.

 

[Sue Wilkinson]

When you point with a metal tool, the tool brings the lime to the surface and leaves a smooth latence. Most of us use a brush to knock this off and expose the aggregate to lessen the whiteness of the work. I guess you just leave it as it is. The lime on the surface like that isn't strong though and will wear away quickly leaving the aggregate behind showing eventually.

When you mix the mortar it will look dark and drab. Its only when its dry that it will be white.

Sue

 

[monkey writer]

I'm going to need to repoint the space under the front steps as you can see through to the neighbour's area in places...!

These walls are always quite damp but, although they are outside, they never have any direct rain or frost on them as they are under the steps. Can I use non-hydraulic lime, or should it be hydraulic lime for this?

Also, the chimney needs repointing - hydraulic or non-hydraulic lime for this?

Thanks!

 

[Gervase]

If it stays damp as in green and soggy damp, then hydraulic is probably best. If you're going to be using the same stuff for the chimneys, I'd say to go for a few bags of an NHL 3.5, but otherwise an NHL2 wouldbe fine for under your stairs. Either would be mixed 1:3 with sharp sand.

It depends on your chimneys, though. You could get away with an NHL 2 for repointing them as well if you're not too exposed. Current thinking, however, seems to be to use an NHL3.5 for most stuff above the roof line, and even an NHL5 for the flaunching on the top of the chimneys and for bedding ridge tiles.

 

[monkey writer]

Thanks!

I'm probably going to buy it from http://www.mikewye.co.uk and they seem to recommend:

Lime Mortar Unhaired 3.5 mixed with Metastar 402 (8 -12% by volume)

Does this sound acceptable?

 

[NT]

Why mix hydraulic lime with pozzolan, instead of buying NHL5?

NT

 

[Gervase]

There's more fat or 'free' lime in the less hydraulic types, which means that it's better at autogenic healing in the event of cracking or movement.

 

[monkey writer]

I'm getting confused again! But I think it's my mistake in the posting.

I meant to put Mike Wye Lime Mortar Unhaired 3.5/1 - which I assume is a non-hydraulic lime mixed with sand in the ratio 3.5 sand to 1 lime. I'd better check that.

Assuming it is... would that mixed with a pozzolan make a suitable mortar for chimney and a damp external under stairs?