If you own a period property, you may already know that the floor beneath your feet matters more than most people realise. The wrong type of floor in an old building can cause damp, push moisture into your walls, and slowly damage the very fabric you’re trying to protect.
It’s a problem we see all the time. A well-meaning owner installs a modern concrete floor in a historic home, and within a few years, walls that had stood happily for centuries suddenly start showing signs of damp and decay. It’s one of the most common issues we encounter, and one we discuss in more detail in our guide to common problems and solutions in period properties.
This is where limecrete floors come in. They’ve been around for a long time, they work brilliantly in old buildings, and at Emmerson Critchley Ltd we install them regularly across Suffolk and Cambridgeshire, including, on one memorable occasion, beneath the underfloor heating of a Grade I Listed church.
Here’s everything you need to know.
A limecrete floor is a breathable solid floor made using a natural hydraulic lime binder and a lightweight aggregate. Unlike a modern concrete floor, which is dense and traps moisture, limecrete allows water vapour to pass through it freely.
That single property, breathability, is what makes it so valuable in period homes.
Old buildings were designed to breathe. Solid walls, lime mortars and renders, timber frames and clay tiles all let moisture move in and out naturally. When you introduce a non-breathable layer at floor level, that moisture has nowhere to go. It gets pushed sideways, into the walls, where it causes the kind of damp problems that plague so many incorrectly renovated period homes. A limecrete floor solves that problem at the source.
Modern concrete floors are brilliant in modern buildings. They’re strong, fast to lay, and play nicely with the damp-proof membranes used in contemporary construction.
In a period property, though, they cause more problems than they solve. Here’s what typically happens.
The concrete slab traps ground moisture beneath it. With nowhere to go upwards, that moisture migrates outwards, finding the path of least resistance, which is usually straight into the base of your walls. The result is rising damp, rotting timbers at floor level, damaged lime plaster, and a general sense that the building is fighting against itself.
By the time these problems become visible, they’re usually expensive to put right. This is exactly why period properties need a specialist builder who understands traditional materials and methods.
A proper limecrete floor is a layered system, and each layer has a specific job to do. Here’s exactly how we build one.
The very first layer to go down is a geotextile membrane, which acts as a weed and root barrier between the ground and the rest of the floor build-up. It is a simple step, but it protects everything above it.
Next comes the insulating base layer. We use Glapor, a lightweight foam glass aggregate made from 100% recycled glass. It comes in lumps of roughly 40 to 70mm, and the size matters. The larger pieces create air gaps that make it physically harder for water to track upwards by capillary action.
This layer needs careful handling. It must be compacted by no more than 20mm. Over-compact it, and you lose some of the air structure that gives the floor its U value. Worse still, an over-compacted base can start to wick water rather than block it. It’s one of those areas where a contractor who genuinely understands the material makes all the difference.
A second geotextile membrane is laid over the Glapor layer. This acts as a separation barrier between the foam glass base and the screed above it, keeping the two layers cleanly separated during installation and over the life of the floor.
The structural top layer is an aggregate screed bound with NHL5, a natural hydraulic lime. It goes in at a minimum of 100mm thickness. This is the part of the floor you’ll eventually walk on, either directly with a finish applied, or with floor coverings laid on top.
If you want underfloor heating in your limecrete floor, this is the stage at which it is installed, embedded within the screed itself. You can see one of our recent limecrete installations here.
The combination of underfloor heating and a limecrete floor is one of the most satisfying pairings in heritage work.
Limecrete has good thermal conductivity, which means the heat from the underfloor heating system transfers efficiently into the room. The breathability is preserved, the warmth is even, and you get all the benefits of modern comfort without compromising the building’s natural fabric.
We’ve installed limecrete with underfloor heating in everything from small cottages to that Grade I Listed church we mentioned earlier. When it’s done properly, the floor warms up beautifully and the building keeps doing what it was designed to do.
One of the things we love about limecrete floors is how they help disperse moisture across the floor area rather than letting it concentrate in any one place. That’s why a properly installed limecrete floor can dramatically reduce damp problems, particularly the kind of corner damp that many period property owners struggle with.
But here is something important to understand. If you’re seeing damp in the corners of your rooms, the floor on its own may not solve the issue. Corner damp is often the result of several factors working together. It could be that the external ground level is too high, allowing rainwater to track inwards. It could be that the property needs a French drain to redirect surface water away from the walls. It might be a combination of both, plus an internal floor that’s pushing moisture sideways.
This is why we always look at the whole building rather than just the floor. A new limecrete floor is a brilliant intervention, but for it to perform at its best, the walls and the surrounding ground need to be doing their job too.
While we’re on the subject of how the floor works alongside the rest of the building, it’s worth talking about the walls.
For a limecrete floor to deliver the thermal performance it is capable of, the external walls should ideally be finished with a cork lime render. This combination of breathable cork insulation and lime render does two things at once. It prevents direct heat loss through the wall fabric, and it improves the overall U value of the building, working in harmony with the breathable floor below.
It is the kind of joined-up thinking that separates a really successful heritage retrofit from one that only does half the job.
The installation itself is not slow. The slow part is the curing. Limecrete cures by carbonating with the air, and that takes time. You’re typically looking at several weeks before the floor can take significant load, and longer still before a final finish can be applied.
For most projects, we’d say to plan for around six to twelve weeks between starting the floor and being able to use the room normally. It is worth the wait.
We believe in being straight with clients, so here is the balanced view.
The pros are significant. Limecrete is breathable, sustainable, made from natural materials, and works with the building rather than against it. It dramatically reduces the risk of damp in walls. It pairs beautifully with underfloor heating. It uses recycled aggregate. And it lasts an exceptionally long time when installed correctly.
The cons are mainly about time and patience. Limecrete takes longer to install and cure than a modern concrete slab. It is a more specialist material, which means fewer contractors know how to work with it properly. And the upfront cost can be slightly higher than concrete, although over the lifespan of the building, it tends to look like a bargain.
In our experience, a limecrete floor is the right answer when:
It is not always the right choice for every project. Modern extensions on period homes, for example, often work best with conventional concrete. We will always talk you through what is right for your specific situation as part of our wider restoration and conservation work.
We’ve been installing limecrete floors across East Anglia for years. We understand the material, we know how to specify it correctly for different applications, and we have the experience to get the build-up right first time. From small cottages to listed churches, we’ve laid floors that will outlast every one of us.
If you’re considering a limecrete floor for your period property, or you’re struggling with damp problems that you think might be linked to your existing floor, we’d love to have a conversation.
Get in touch with our Bury St. Edmunds team on 01359 240 573 or email sales@emmersoncritchley.co.uk.
