The Hidden Enemy: Why Your Stone Walls (and Wallet) Deserve the Right Mortar

If you own a period home, a charming cottage, or even just a lovely old stone garden wall in Bath or Bristol, you've probably heard the word "repointing." It sounds simple, right? Just fill the gaps between the stones. But as a stonemason, I can tell you that what goes into those gaps can make or break your wall and even your house.

This isn't just about making things look tidy; it's about protecting your biggest investment. And the hidden enemy? Often, it's something called cement.

A Tale of Two Mortars: When Good Intentions Go Bad

Imagine a beautiful old stone wall, standing strong for a century or more.

Back in the day, before modern cement was widely available, these walls were built and repaired using lime mortar. Lime is softer, more flexible, and crucially, "breathable." It allows moisture to enter and leave the wall naturally, just like your skin allows you to sweat. This gentle process keeps the stone healthy.

Then, after World War II, cement became popular. It was cheap, quick, and set hard. Many well-meaning builders (and DIY enthusiasts) started using it on old stone walls, thinking "harder is better."

This is where the problems begin.

The "Cement Trap": Why Harder Isn't Always Smarter

Cement is like putting a plastic bag over your wall. It's incredibly hard and completely non-porous. When moisture inevitably gets into an old stone wall (and it always does, especially in our damp UK climate), that cement mortar traps it. The water can't evaporate through the mortar, so it's forced to find the next easiest way out: through the stone itself.

• Stone Sacrifices Itself: Since old stone (like our beautiful Bath Stone) is generally softer than cement, the trapped moisture causes the stone to decay. It spalls, flakes, and crumbles, often at an alarming rate.

• Cracks Appear: The rigidity of cement means it doesn't move with the wall as temperatures change. This leads to cracking, which lets more water in, creating a vicious cycle.

• Structural Damage: Over time, this constant dampness and decay can compromise the structural integrity of your wall, whether it's a garden boundary or a load-bearing wall of your house.

What started as a seemingly cheap, quick fix with cement can quickly become a very expensive problem.

The Power of Lime: Breathing Life Back Into Your Walls

This is why lime mortar is almost always the correct choice for repointing old stone walls, whether they're on your house or in your garden. It respects the original construction and works with the stone, not against it.

• It Breathes: Lime mortar is permeable. It allows moisture to pass through it, keeping your stone drier and healthier.

• It's Flexible: It can gently expand and contract with the wall, preventing cracking.

• It's Self-Healing: Over time, lime mortar can even 'heal' hairline cracks by reabsorbing carbon dioxide from the air.

• It Looks Right: The softer texture and natural colours of lime mortar perfectly complement traditional stone, maintaining the authentic character of your property in Bath or Bristol.

Don't Let Good Intentions Lead to Bad Outcomes

Repointing isn't just a maintenance job; it's a specialist craft that directly impacts the health and longevity of your stone walls. Using the wrong materials can cause far more damage than doing nothing at all.

If you have crumbling mortar, flaking stone, or even just some old, hard cement pointing that's making your beautiful stone look sad, it's time to act.

Get in touch with AXW Stonemasonry today. We understand the nuances of stone and mortar, and we're passionate about using the right materials to protect your property for generations to come.