What Is Roughcasting and Is It Right for Your Scottish Home?

What roughcasting actually is

Roughcasting is a finish for outside walls. Small stones or chips are mixed into the last coat of render, then thrown onto the wall while it is wet. In Scotland you will also hear it called wet dash or harling. Harling is the old lime-based version you see on older stone buildings and castles. The result is a textured, slightly lumpy surface instead of a smooth one.

It is different from dry dash, where the chips are thrown onto a smooth wet render and stick to the surface. It is also different from modern smooth or thin-coat renders. With roughcast, the stones are part of the mix itself, which makes the finish dense and hard-wearing. A typical job has a scratch coat, sometimes a second levelling coat, then the roughcast coat on top.

• Wet dash or roughcast: chips mixed through the final coat and cast on
• Dry dash: chips thrown onto a fresh smooth coat, giving a more uniform look
• Harling: the traditional lime version, right for pre-1919 stone houses

Why it suits the Scottish climate

The main reason roughcast is everywhere in Central Scotland is driving rain. Stirling and Falkirk sit in one of the wetter, windier parts of the UK, and rain here often comes in sideways. The rough surface breaks up water running down the wall and throws it off. On a smooth finish, water can run down in a sheet and find its way into fine cracks.

It is also forgiving. Smooth render shows every ripple in the wall underneath and every fine crack that appears over the years. Roughcast hides small faults and movement cracks far better. That matters on older walls, which are rarely perfectly flat. Done properly with the right mix, roughcast should last 30 to 40 years or more. It needs very little care beyond an occasional wash or repaint.

When roughcast might not be the right choice

The honest answer is that it is not for everyone. Some people simply prefer the crisp look of a smooth or thin-coat render, especially on new builds and extensions. There is nothing wrong with that, as long as the edges around sills and copes are done well. Roughcast is also harder to patch so it does not show. Matching the texture and stone size of a 30 year old wall takes skill, and a poor patch will always show.

The bigger issue is the wall behind it. If your house is traditional stone built, typically pre-1919, it needs a lime-based harl that lets the wall breathe. A strong cement roughcast on old stone traps moisture, and that is a common cause of damp inside older properties around Stirling. Once the wall has dried out, the damp plaster inside can be replastered. Likewise, if existing roughcast is hollow when tapped, or blown in patches, rendering over the top is a false economy. It usually needs stripped back and redone properly.

What affects the price

The cost of a new roughcast depends on how much wall there is. It also depends on whether the old finish has to come off, and how much scaffolding the house needs. A small gable or one wall is much less work than a whole semi. Every wall is different, so we look at it for free and give you one fixed price before any work starts.

The main things that change the price are scaffolding and how much old render has to come off. The state of the wall underneath matters, and so does whether you need lime instead of cement. Repairs to cracked or worn stonework can add cost, but they are worth doing while the wall is bare. A written quote from someone who has tapped and checked your walls is worth far more than any figure online.

Common questions

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