Solid walls in period properties
If you're buying a Victorian, Edwardian or earlier property, there's a good chance at least some of the external walls will be of solid construction.
For buyers accustomed to modern cavity walls, the term "solid wall" can sometimes sound concerning. Does it mean the property is more susceptible to damp? Will it be cold? Does it need insulating?
Solid walls aren't inherently defective. They simply work differently from modern construction, and understanding those differences is important when maintaining or altering a period property.
What is a solid wall?
Modern houses are typically constructed with two separate leaves of masonry with a cavity between them.
Many older properties were instead built with solid brick or stone walls, without a cavity separating the internal and external faces.
In brick properties, wall thickness can sometimes provide an initial clue. Traditional solid walls are commonly around one brick thick, although construction varies considerably depending on the age and type of building.
Stone properties can have significantly thicker and more irregular walls.
How do solid walls deal with rain?
A common misconception is that historic walls were intended to be completely waterproof.
Traditional solid walls generally manage moisture by absorbing a degree of rainwater during wet conditions before allowing it to evaporate again as conditions improve.
The materials traditionally used alongside them, particularly lime mortar and lime plaster, help this process.
This is one reason why understanding breathability is so important when dealing with historic buildings.
Are solid walls more likely to be damp?
Not necessarily.
A solid wall that has performed successfully for 100 or 150 years doesn't suddenly become defective simply because it lacks a modern cavity.
When dampness does occur, the cause should be investigated rather than automatically blamed on the wall construction.
Common contributing factors can include:
Defective gutters and downpipes
Damaged pointing or render
Raised external ground levels
Poor ventilation
Plumbing leaks
Inappropriate modern finishes
Understanding why moisture is present is far more useful than simply identifying that the building has solid walls.
Modern materials can change how the wall performs
Problems can arise when traditionally constructed walls are covered with materials that significantly restrict evaporation.
Hard cement renders, impermeable coatings and some modern internal finishes can change the way moisture moves through the wall.
If moisture enters but cannot readily escape, deterioration can become concentrated within the masonry or internal finishes.
This doesn't mean that modern materials are universally unsuitable. It means repairs and alterations should be considered in the context of the existing construction.
What about insulating solid walls?
Improving the energy efficiency of historic buildings is understandably becoming increasingly important.
However, insulating a solid wall isn't always as straightforward as filling a cavity.
Internal or external wall insulation can alter the temperature and moisture behaviour of the existing wall. If poorly designed or installed, this can increase the risk of condensation and trapped moisture.
That doesn't mean solid walls cannot be insulated successfully.
It means the proposed system needs to consider the building as a whole, including its construction, exposure, ventilation and existing condition.
Look at previous alterations
When surveying a period property, I also consider how the walls have changed over time.
Has the property been rendered?
Has cement pointing replaced the original lime mortar?
Have internal walls been dry-lined?
Has an extension introduced cavity wall construction alongside the original solid walls?
A single property may contain several different forms of construction, particularly where it has been extended and altered over many decades.
Recognising these differences helps explain why certain parts of the building may behave differently from others.
Solid wall construction isn't a defect
Perhaps the most important point for buyers is that solid wall construction shouldn't automatically be regarded negatively.
Millions of historic properties were built this way and continue to perform successfully today.
The key is appropriate maintenance.
Trying to make a traditional solid-walled property behave exactly like a modern cavity-walled house can sometimes create more problems than it solves.
Final thoughts
Solid walls are a normal and fundamental part of many historic and period properties.
They manage moisture differently, respond differently to alterations and require a different approach to repair and maintenance than modern cavity construction.
For anyone buying an older property, understanding how the walls have been constructed, and whether previous repairs are compatible with them, can provide valuable insight into the condition of the building.
Older construction isn't necessarily inferior construction. It simply needs to be understood on its own terms.