Isn't lime mortar just for old buildings?
Written by a Human, not AI
At Studio Barn we're big fans of lime mortar for lots of reasons, and here are some of them.
Lime mortars lets walls manage moisture naturally
Cement mortars trap water, taking it longer to dry out. Lime mortar allows water vapour to move through the construction. Breathability matters for healthy buildings, especially where natural insulation is being used.
Lime is more forgiving
Lime mortar can accommodate small amounts of movement in brickwork, reducing the likelihood of cracking. This can be of particular note in the first few months of a buildings life, as the building settles. Historic buildings can shift on the foundations with seasonal changes, and lime can help absorb this impact; unlike cement (which can be harder than the brick itself), lime can recrystallise and seal small cracks naturally.
Lime can reduce efflorescence
That unattractive white salt that appears so frequently on new brickwork? It’s more likely to appear on buildings using cement mortars as water is trapped there longer on each course and has more time to draw out salts, as a cement-based mortar has a much tighter pore structure and substantially lower permeability than lime.
Cement doesn't make a joint waterproof, it just significantly reduces water movement through the joint, meaning water that might normally escape a brick by gravity or evaporation is greatly slowed down. So you can end up with damp appearing higher up a wall, salt crystallisation appearing on brickwork, and spalling (where the surface of the brick breaks away) during a freeze and thaw.
Damp is a complicated and sometimes controversial topic, but a wall that is wetter longer, is also colder longer, and then more prone to condensation on internal finishes. Water rises through masonry, stone and mortars via capillary action (a slower version of what you see when dip a piece of paper in water) and the tiny interconnected pores in each. This process tends to be limited mainly by gravity and evaporation. A lime mortar becomes the path of least resistance for water evaporation, making it easier for water to escape from the wall construction at each course. A cement mortar doesn't allow evaporation anywhere near as easily, so capillary action continues up the wall, and any water that does migrate out via the bricks themselves, can then take natural salts with it to the surface,
And even worse, the practice of using washing-up liquid to make it easier to spread cement can add even more salt to the problem, and the Brick Development Association warns against its use for this reason.
In short, a lime mortar is breathable, helping making the natural movement of water through a wall easier so it doesn't trap it in the wall.
Credit: Richard Bossons
Lime makes brickwork reusable and more repairable
If you've ever had to to clean up bricks for re-use, you'll know that it is so much easier to chip off lime mortar than bricks bonded together with cement mortar. Cement may last longer as a joint, but lime can help the masonry last longer as a wall.
You might not need to repoint a lime mortar wall for 30-50 years, but it will be so much easier (and less damaging to brick) when you do, than mechanically cutting out the cement.
Today’s wall doesn’t need to become tomorrow’s rubble. We all need to make whole life cycle choices when it comes to buildings, and consider how materials are ultimately recycled.
Lime mortar looks so much better…
Seriously, it’s not even a contest. The material costs a little more, and the build programme needs to allow for proper curing time, so find a progressive contractor who can manage this!
So why did using lime mortar fall out of favour?
Faster-setting, stronger and less dependent on weather conditions meant cement became the industry default; and it basically de-risked it for contractors.
But cement mortar is not the best choice for healthy buildings or the environment.