Lime Mortar on New Build

[BadgerBadger]

We're starting a new build with fairly standard brick/block construction.  We're aiming for a pretty high standard external finish and are planning to use a handmade brick.  Any thoughts on the pros and cons of using a lime mortar (e.g. a pre-mixed bagged natural hydraulic lime) on a new build?  Is it likely to be significantly different for a bricklayer to use? (i.e. do I need a specialist!) 

 

We also have some areas of double-skinned wall - can I combine a cement-based mortar for the inner blockwork when it's right next to a lime-based mortar for the outer facing bricks?

 

Thank you!

[Onoff]

Lime...ask 10 people get 10 different answers I've found! 

[Brickie]

A ‘specialist’ may be overkill but,in your shoes,I’d want someone with experience of lime,preferably having  built something similar. 
Speak to the rep of whichever company you’re planning on buying the line mortar from. Ask for common pitfalls (how high shoulda wall be taken in one hit? How long to cover with hessian in cold weather?) to help you gauge if a potential contractor knows their stuff or is just blagging it. 
The rep may even be able to give you  a number or two. 

[SteamyTea]

1 hour ago, BadgerBadger said:

Any thoughts on the pros and cons of using a lime mortar

Why lime mortar?

[BadgerBadger]

10 minutes ago, SteamyTea said:

Why lime mortar?

 

Our key driver is aesthetics - we're sat near some historic buildings, and our general approach is to go for high-quality materials that give us a "traditional" appearance without pretending our house is old.  So our thinking is if lime (alongside handmade bricks) could give us a softer more natural finish than cement based mortar, but weighing up if it's worthwhile for any potential costs and other disadvantages.

 

I think there's a few arguments around using lime alongside handmade bricks where the more open texture might allow more moisture in, and the breathable lime helps allow it out again.  But not sure how valid that is!

[saveasteading]

My only 2 experiences of lime are;

1. lime plaster  on existing lath inside a listed building, insisted on by the planner. It cost £1,000 for 6m2, because very few people did it.

2. converting a masonry farm building.  the masons use lime as standard. as well as being the right solution technically , I think it is easier to work with.

 

For bricklaying I would fear that 1) is more relevant and you might find resistance/reluctance among the brickies....best make some enquiries as suggested.

 

There is less need for lime mortar in brick walls in modern times. The buildings don't move so much as the foundations are deeper, so don't need to self-repair. The walls are cavity construction and moisture does not get in past the outer skin.

[SteamyTea]

15 minutes ago, BadgerBadger said:

 

I think there's a few arguments around using lime alongside handmade bricks where the more open texture might allow more moisture in, and the breathable lime helps allow it out again.  But not sure how valid that is!

My mother's house, 1974 vintage, has hand made bricks, but with a normal cement based mortar.

There has been no failures in it yet.

 

One word of caution about hand made bricks, they are hard to match up if you build an extension later. The brickwork company closed down about 20 years ago, so the workforce has probably died off as well.

[nod]

You may be worth costing the handmade bricks if you haven’t already done so and kind motar also 

Unless budget isn’t an issue You May be quite shocked 

 

[Temp]

I tried to read up on lime mortar before we built our place but also got differing opinions. Some places say its not real lime mortar if its got any cement in it. Others dissagree. In the end our bricklayers recommended a lime cement mix they had used with our bricks on a garden wall I could go look at. Glad I went with their recommendations. Thus may seem odd but it looks more sandy than cement only mortar.

 

Whatever you decide  I recommend you get them to build a sample wall about 1m x 1m using the bricks and mortar mix you propose somewhere in a corner of the site. You can tell them it's to check if the motor mix will look right but also use it as a QA sample.

 

 

[Temp]

6 minutes ago, nod said:

You may be worth costing the handmade bricks if you haven’t already done so and kind motar also 

Unless budget isn’t an issue You May be quite shocked 

 

 

We were going to use hand made bricks but planners rejected them as having too much texture. Ended up using a mix of Audley Antique and another similar brick which I forget the name of..

 

https://www.travisperkins.co.uk/facing-bricks/traditional-brick-and-stone-facing-brick-audley-antique-pack-of-600/p/621571

 

Pretty happy with the result and was able to spend more on the roof tiles.

 

Edited September 18, 2021 by Temp

[Stewpot]

Just to preface this, I am by no means an expert. By no means. The more I find out about using lime in building work, the more, I realise, I don't know. But I have used it a little over the years, have read lots about it, and plan in using it in my own build (if the planning department ever get around to my application).

 

Mixing and using lime mortar is a little different from a more usual Ordinary Portland Cement mix. For a start, you need to be more exacting about the quantities you use. Whereas with OPC you can make a perfectly good mix by measuring it out by rough shovelfulls, you will need to be more accurate than that with a lime mix. Many people would use a pan mixer for lime, as it can clog and ball-up in a barrel mixer, and generally require more attention. And be careful with the water. If you're mixing from lime putty (non-hydraulic lime), you may not need to add any extra water at all. To an extent, a stiff mix becomes more pliable, the more you work it, so give it plenty of time in the mixer.

 

Using it can be a nicer experience than an OPC mortar - a good mix is workable and pliable stuff, has a much longer open time, and can be re-knocked up to bring it back to life. The long curing time of lime means that you have to give it some after care. Keep it damp and protected from direct sunlight to help prevent it drying out for at least a couple of weeks, and this will help carbonation to continue throughout the depth of the mortar. It may take months, or even years for the full curing process.

 

You wouldn't want to use OPC and lime mortars in the same element, but if they are discrete units - ie. they don't form part of the same structural element - you may be able to do that. But why, if you are going to the trouble of using lime mortar, would you be using OPC in an adjacent element? A major advantage of lime over OPC is that it is 'flexible' - ie. if the building settles or moves a little, the lime will be able to accommodate this. It has a very long curing time, and to a certain extent cracks can be self-repairing.

 

The other main advantage of lime is that it is vapour permeable, so it enables wet masonry to dry out, and can help with problems like rising damp. Some will tell you that it's permeability improves the internal atmosphere and living environment, too.

 

A hydraulic lime mix is more like OPC than a non-hydraulic mix, as it has a faster initial set. To some extent there is a trade off between the advantages of lime and this quick set time, but you will still have to give it the same after care in order for it to reach its full strength.

 

As lime mortar is not generally used these days, and its differences from OPC are no longer well understood, there is an assumption on the part of many builders that it is basically just the same stuff. I would want to be using a builder who is experienced with it (as opposed to someone who says "Oh, yeah, I've used it before"). Some builders also make the mistake of thinking that hydraulic lime is the same as hydrated lime, and as the latter is easily available in builders merchants for use as an admix in OPC mortar, these builders sometimes think they are experienced with a lime.

[Stewpot]

2 hours ago, Onoff said:

Lime...ask 10 people get 10 different answers I've found! 

 

Ain't that the truth.

 

However, I find that if you ask people who actually know and understand the stuff, this doesn't happen (so much).

Edited September 18, 2021 by Stewpot

[epsilonGreedy]

2 hours ago, BadgerBadger said:

Our key driver is aesthetics - we're sat near some historic buildings, and our general approach is to go for high-quality materials that give us a "traditional" appearance without pretending our house is old.  So our thinking is if lime (alongside handmade bricks) could give us a softer more natural finish than cement based mortar, but weighing up if it's worthwhile for any potential costs and other disadvantages.

 

 

You can achieve a lot with "bagged" pointing, white cement and a mixed granular sized sand that colours the white mortar and produces a rough granular finish when rubbed. I only learned about mixed granular sand after my walls were up even so I am pleased with the finish using bagged pointing, white cement and a sand with a rich yellow colour.

 

There are other details where you can spend money to age a property:

• Roof drainage gutter hoppers.
• External soil pipes.
• Cast aluminium gutters.
• Trad chimney pots.
• A couple of courses of grey bricks in a chimney flare.
• Low rise window cills rather than 150mm commodity modern estate cills or even white painted concrete cills cast onsite.
• No window recess or full brick window reveal rather than mainstream half brick reveals.
• Fat walls up to knee height.
• Brick corbels at gutter height.
• Contrasting brick colour two or tree courses above ground level.
• Fan light above the front door.
• Wisteria growing up the front wall. 

[ToughButterCup]

Handmade bricks eh? Hmmm, where's Ed,   ( @Construction Channel ) when you need him? Didn't he make some  - as in his watchword  'How Hard Can It Be ' ? 

 

When we took our piggery down, we found that the bricks had been made by hand  at our local brickworks. Couple of retired builders walked past , eyed the stacked bricks on the pallets: nodded at them and said

 

"Tidy stack, tidy stack lad, 'ang on to um . "

 

No, it was'nt  @nod who said that (he isn't retired -yet) , but they each of them know how much a handmade brick costs. And Rollo bless his cotton socks stacked mine for me after I had roasted him for throwing many of them in the skip. 

 

Made him climb back in the skip and get them all out. And stack each one of them properly with love and affection. Well, his first stack fell over: he'd never looked at a stack of bricks before. Amazin' wot yoof don't look at innit?

 

" Distinctly uncool Mr Simpson, distinctly uncool"

"Lad, if I charge you for the ones you threw in't skip, you'd owe me money: as it is I've paid for you to throw them in, now I'm bloody paying you to take the foookers back out"

"Okey, ya ... ... really? " 

 

He's now working for a builder.

[saveasteading]

1 hour ago, Stewpot said:

permeability improves the internal atmosphere and living environment, too.

But doesn't get past the plastic lining on the inside of a modern house...effectively living inside a plastic tent with a building around it.

 

9 minutes ago, epsilonGreedy said:

details where you can spend money to age a property:

Good list Epsilon.   You forgot the Outside toilet?

[Bonner]

+1 for white cement. My new build brick house was specified with lime mortar by the architect. Brickies made a sample with white cement, looks just like lime mortar I have used before on a period property. 

[Faz]

White cement on mine and the spec ones - looks great with red or buff bricks.

 

 

[Stewpot]

1 hour ago, saveasteading said:

3 hours ago, Stewpot said:

permeability improves the internal atmosphere and living environment, too.

But doesn't get past the plastic lining on the inside of a modern house...effectively living inside a plastic tent with a building around it.

 

Well, yes. But no.

 

If you've designed the building with lime in mind, you wouldn't then go and ruin one of it's advantages (vapour permeability) by installing a VCL.

 

Really, you highlight the point that building with lime is not just like building with OPC, but quainter. Building with lime can offer advantages, but to make the most of them, it also requires a different approach to the philosophy of the building.

 

Some people confuse vapour permeability with air tightness - they are not the same thing, but the common (mis)use of the word 'breathability' often makes people think they are.

 

 

[SteamyTea]

4 hours ago, Bonner said:

+1 for white cement.

And it will set hard, consistently.

2 hours ago, Stewpot said:

Some people confuse vapour permeability with air tightness - they are not the same thing, but the common (mis)use of the word 'breathability' often makes people think they are.

Probably quite hard to get decent airthightness numbers without an installed membrane that is specifically for that purpose.

The MVHR takes care of the moisture in the house and recovers the some energy.

[Gus Potter]

8 hours ago, BadgerBadger said:

 

Our key driver is aesthetics - we're sat near some historic buildings, and our general approach is to go for high-quality materials that give us a "traditional" appearance without pretending our house is old.  So our thinking is if lime (alongside handmade bricks) could give us a softer more natural finish than cement based mortar, but weighing up if it's worthwhile for any potential costs and other disadvantages.

 

I think there's a few arguments around using lime alongside handmade bricks where the more open texture might allow more moisture in, and the breathable lime helps allow it out again.  But not sure how valid that is!

Interesting stuff.

 

"Our key driver is aesthetics." 

 

It's about 20 years ago that this cropped up for me the last time. We were talking about using concrete blockwork and brickwork in lime mortar to avoid having to introduce movement joints.  Standard UK spec is say joints in concrete blockwork at 6.0 centres / brickwork at 9.0 m centres. We looked at lime mortar and as it was mostly concrete block decided not to take the plunge and spec it, knees got a bit wobbly! Fine on old stonework..but!

 

But BadgerBadger.. hey, hand made bricks. There is a massive attraction here as you are maintaining the ethos. I commend you for that. Concrete blocks pretty much shrink over time and that's it. But clay bricks are arguably more lively and natural". They expand a fair bit in the heat, swell / shrink as the humidity changes and just move a bit as they age and weather.

 

I'm not sure how this may stack up for you but if you have say a feature elevation of a decent length and going for the real deal with hand made bricks with a traditional clay mix then much will depend on you own personal desire. However, if you have a fair expanse of brickwork having a movement joint visible kind of defeats the purpose? And that drives you towards a soft flexible lime mortar which could do some 12 - 15m run? that much? without a joint or return corner to relieve the stresses?

 

The other thing is whether you have a timber frame on the inside or are using a cavity masonry wall. If you're doing this then the regs on venting TF cavities could be a "damper" but with cavity masonry construction maybe easier to deal with?

 

There is no doubt that it will cost you more but if you are going to do, it do it right and enjoy. Some folk buy paintings others build walls and get to see them every time they get home and walk in the front door. I would make sure that you don't get hung up on some building regs that require you to put in say plastic cavity vents. Solum vents would be ok as you could really go to town and get authentic reclaimed vents!

 

Now I've just spent all your money!

 

 

 

 

 

 

 

 

 

 

 

 

 

[Onoff]

If I recall correctly, then @Construction Channel found by chance that brick clay had been extracted historically from a field on his family's land. He promptly went and dug some up and cast an E&F plaque to go on the gable. From memory his attempts cracked and crazed.

[Onoff]

Ed's brick making:

 

 

[scottishjohn]

I could be totally wrong  and correct me  if I am 

but why not build with cement -but rake out deep when building before its set --then point with what ever you like to get colour and look you want ?

 real lime mortar takes much longer to dry and must be protected from rain etc while its drying or it will dissolve and stain bricks  also  courses  of build per day is much less

 lime mortar as they use for old historic stone work etc can take days or weeks to go off in cold damp conditions 

 or maybe you don,t really mean true lime mortar ,but cement /lime mix

[Construction Channel]

9 hours ago, Onoff said:

If I recall correctly, then @Construction Channel found by chance that brick clay had been extracted historically from a field on his family's land. He promptly went and dug some up and cast an E&F plaque to go on the gable. From memory his attempts cracked and crazed.

Yup thats exactly what happened. I still havent made it ?

[Onoff]

32 minutes ago, Construction Channel said:

Yup thats exactly what happened. I still havent made it ?

 

Well you have been busy...