Bearing the brunt of British weather from all angles, freestanding garden walls need to withstand high winds, heavy rain and frost, as well as heat at the height of summer. Couple this with wear and tear from passers-by (both pedestrian and vehicular), age and the environment, it is no surprise that garden walls are more prone to damage and collapse than other forms of masonry (gov.uk).

If you have a garden wall on your property, you will no doubt be aware of your responsibility as a homeowner to ensure it is safe. According to gov.uk, garden walls are the most common cause of death from falling masonry. This is particularly pertinent for homeowners with garden walls bordering pavements and public rights of way; if the wall is unsafe and causes injury or death, you could be liable. What is more, if the wall was found to have not been properly maintained, your home insurance may not cover it.

Routine maintenance most often involves periodic inspection of the wall for signs of damage or defects, and acting accordingly (requiring expert advice in some cases). Additionally, it is essential to inspect the wall after severe weather (such as high winds and storms).

The following article outlines common signs of damage or defects to look out for when checking your freestanding garden wall, and permissions you might need for repair works.

Blown mortar and/or bricks

The fact that freestanding garden walls are entirely exposed to the elements means they are particularly vulnerable to water damage from rainfall or frost. If water penetrates mortar joints in winter, it will expand when it subsequently freezes, causing the mortar to blow (or ‘spall’). If water gets into the bricks and freezes, the bricks could similarly blow. Ideally, walls with blown mortar should be repointed, and blown bricks replaced. It might be that the measures in place to prevent water damage, such as capping/coping, are defective and needs attention too. Most bricklayers will be able to repoint and replace bricks, but some are repointing specialists. Depending on the scale of the repair work needed, it might be worth going to a repointing specialist.

Crumbling mortar or brickwork

The brickwork of even the sturdiest wall will age over time and suffer general wear-and-tear. Building Control Solutions advise to look out for crumbling bricks and mortar that can be easily scraped away, and warn that sections of extensive crumbling may need rebuilding.

Leaning

Freestanding garden walls can lean for a number of reasons, including damage to foundations (e.g., from damaged drains, heave, or insufficient foundations being in place). Some degree of leaning is not always a cause for concern, and the extent to which leaning is acceptable will depend on the dimensions of the wall. Whilst there are some remedial works that could be carried out to deal with a leaning wall, such as building buttresses, it might be necessary to have the wall rebuilt. Have the wall surveyed to determine whether the wall is compromised, the cause of the lean, and the best course of action to ensure the risk of collapse is minimised.

Loose or damaged coping or capping

Coping and capping help protect freestanding garden walls from rain and frost, ensuring the brickwork and mortar joints of the wall do not become saturated with moisture and suffer damage as a result. Coping stones or bricks protrude beyond the brick wall below, whilst capping bricks or stones lie flush with the wall.

When inspecting your garden wall, firstly check whether any coping/capping stones or bricks are loose. Secondly, examine the brickwork below and check for the signs of rain or frost damage (blown bricks or mortar) and/or horizontal cracks. If you spot any of these, the coping/capping is likely not doing its job effectively and the wall might be compromised. In this case the coping might need to be replaced, but the extent of the damage should be assessed by a professional before determining the best course of action.

Cracks

As with leaning, cracks can appear in a garden wall for a variety of reasons, and not all of them are causes for concern. According to Building Control Solutions, hairline cracks (0-2mm in width) are usually innocuous. It is worth noting the presence of hairline cracks and any changes you see over time. For larger cracks (greater than 2mm in diameter) and horizontal cracks, have the wall surveyed to assess its structural integrity and cause of the cracking. Potential causes for these larger cracks include: tree roots (causing heave), insufficient or damaged foundations.

Monitor tree and plant growth

If you have climbing plants growing over your garden wall, keep growth in check to minimise the potential damage to masonry. Aggressive climbers like ivy are not suitable for garden walls with vulnerable brickwork, as their aerial roots can penetrate mortar joints and weaken the structure. Instead, grow twining climbers on a trellis or wire attached to the wall; as the trellis or wire is supporting the plant, rather than the wall itself, these plants will not be able to damage masonry. Additionally, plants growing on trellises and wires can be removed relatively easily, if need be, whereas self-clinging climbers like ivy will leave behind tough aerial roots that are difficult to remove entirely.  See here for a beginners’ guide to climbing plants.

In addition, keeping growth of climbers in check will allow for a thorough visual inspection of the wall, ensuring you do not to miss any signs of damage or defect that might be otherwise hidden by foliage.

Trees near a garden wall can cause a number of problems. As their roots draw water from the soil around the foundations they can shrink the soil and damage the foundations, according to Building Control Solutions. As trees age and their roots grow and expand, the damage can become more significant. Conversely, if trees near a wall are felled, soil expansion can also cause damage to the wall’s foundations. What’s more, branches blown into a wall by high winds can impact the structural integrity of the wall, and changes to the tree’s canopy/crown can increasing wind loading on the wall.

Vigilance is key here: monitor existing trees and any changes to them, and any damage you can see to the wall that may correlate. An arboriculturist would be able to report on the condition and management of the tree, but a structural engineer or surveyor will be able to report on the impact of the tree on the garden wall itself.

Changes to the surroundings

Monitoring changes in the surrounding area is not limited to trees. Building Control Solutions recommends factoring in changes to other aspects of the surrounding area as well. For example: if nearby buildings have been taken down, the wall may face increased wind loading; if there is increased pedestrian or road traffic next to the wall - say a new gate has been installed or a footpath is used more frequently than before due to new local amenities opening- consider the impact this might have on the wall and the risk could pose if not properly maintained (increased risk of damage from road traffic, for example, or from people sitting on or walking along a low wall). 

Works on your garden wall

If your garden wall needs to be altered or taken down, you can usually have this done without Planning Permission, so long as the height of the existing wall is not exceeded. If in doubt, consult your local planning authority.

However, Planning Permission would be required for alterations to, or removal of, garden walls in the grounds of a Listed Building or within a Conservation Area. Similarly, if an Article 4 Direction is in place affecting the property’s garden walls, they cannot be removed or changed without permission from the local authority.

In the case of garden walls that are Party Walls, a Party Wall agreement will be needed between the two neighbours. The cost of repair works might be shared between the parties, unless one party’s negligence has caused the damage to the wall (for example if a dead branch of a neighbour’s tree fell onto the garden wall and damaged it, they would be liable for repair costs).

Summary

Inspecting your freestanding garden wall periodically, and after severe weather, is key to identifying damage or defects in a timely manner and ensuring the wall is structurally sound and therefore safe. In some cases, it will be necessary to have a garden wall surveyed to determine the cause of damage and the best course action. Repair works can range from repointing and replacing blown bricks, to rebuilding part or all of a wall. Properties that are Listed, in a Conservation Area or have Article 4 Directions in place will likely need planning permission for any alterations to a garden wall, or to have it removed.