We get it. You’re staring at the lime mortar in your old house, and you’re seeing it look crumbly or cracked. And soon enough, you’ve rolled up your sleeves, and you’re ready to fix it yourself. But… before you grab a bag of cheap cement for a quick fix, please stop! This is because you could be unintentionally inviting long-term damage.
To keep it brief, cement is a modern material that can be disastrous for historic properties built before the 1930s. And now you might be thinking… how bad can it be?
Well, cement is rigid and non-porous, and historic walls need to “breathe” to manage moisture. So when cement traps this moisture inside, it then forces the softer brick or stone to decay, a process known as spalling.
In simple terms, cement kills old houses.
And at K Blythin, we pride ourselves on revitalising and preserving historic buildings. Which is why we want to share this knowledge with you, so you’ll be able to see:
How to tell your pointing is failing
So first off, your building will give you clear clues that its mortar is failing and needs intervention. This can be easy to spot once you know what you’re looking for, so look for these key signs:
1. Crumbling, sandy joints:
If the mortar between your stones or bricks is turning to dust or is easily scraped out, its binder has failed. This is a clear sign that water ingress, A.K.A. penetrating damp, is imminent, and repointing is urgently needed.
2. Unattractive patchwork repairs:
Look for sections where hard, grey cement has been crudely patched over lighter, softer, original mortar. This is a common warning sign that moisture is being trapped behind the patch, causing severe damage around it.
3. Spalling or flaking masonry:
If the face of your brick or stone itself is flaking, pitting or crumbling away, this is a definite indication that trapped moisture, usually caused by non-breathable cement mortar, is destroying the masonry fabric from the inside out.
What to do once you spot the signs
The essential role of lime mortar
You’ve found the warning signs, but now what do you do?
Well, let’s first introduce you to lime mortar. A natural material used for over 2,000 years that is porous and flexible. Its high void volume allows moisture absorbed by the wall to evaporate outwards through the mortar joints. Hence, this breathability keeps the masonry dry and healthy. Additionally, its flexibility also allows the building to withstand natural movement and settlement without cracking the masonry itself.
So if you spot any of these signs, do not attempt a quick cement fix.
Getting the mix ratio right is a specialised skill, and proper lime pointing starts with sourcing the correct materials, especially the right sand for a seamless blend.
Getting expert help
K Blythin Brick & Stonework Ltd is an experienced, family-run business from Chester with 60+ years’ combined experience in the brick and stone-working trade.
We handle all manner of brickwork and stonework from lime mortar pointing and bricklaying to paving and drystone walls. We work sympathetically on period and listed buildings, so we can help with restoration and repairs to listed properties and buildings of historical importance. So give us a call on 07903 015639 about your historic structure.