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Property Surveying Blog

November 6, 2017

A Look at Subsidence

Written by Karim El Shenawi-Ali

Tree Root DamageAs a Party Wall Surveyor, one of my daily tasks is to undertake site visits, which i inevitably means I will see a wide variety of property defects.  While I have seen many, in my experience I have found defective walls to be most common.

A defective wall is defined as a wall that contains a structural deficiency, if left untreated, this can cause an adverse effect on the structural stability of the building and affect the safety of the building and its occupants.

In this blog post, I’ll aim to provide a sound explanation of possible wall defects, in order to improve your awareness of the surrounding condition of your property.

When assessing a potential defect or failed wall, it is important to consider the number of potential causes for the defect, failure to do so may expose you to the risk of only addressing one factor of the cause as opposed to the whole issue.

Generally speaking, cracking, damp penetration and walls that are leaning can be a sign of a defect and should be addressed promptly.

I have identified two very common forms of defective walls or failed walls.

Tree Roots

The amount of water content located in the subsoil can have a dramatic effect on the condition of the retaining walls and overall structure. Surrounding trees that are in close proximity of the property can dramatically reduce the water content within the soil.

Tree roots act as a mechanism to absorb moisture and provide water and nutrients to the tree. However, roots can grow up to three times the the length of the tree’s branches meaning they will absorb a significant amount of moisture from the soil.

With some trees having the ability to absorb 50,000 litres of water a year, this places a building structure within close proximity at risk as there will be a reduction of moisture within the subsoil. This can result in subsidence, which can be visible upon the external structure of the property in the form of cracking.

Wall Tie Failure

Wall ties are used to tie together the external and internal walls of a property thus allowing the walls to be restrained and stable. Failure to properly restrain or support large areas of the wall can result in the wall bowing or leaning.

Wall tie failure is a very common issue, especially in older properties. A lack of building standards in previous history was a catalyst behind wall tie failure as the methods behind the installation of the wall ties were not adequate enough to provide the sufficient support.

A major example being floor joists running parallel to a wall would have no lateral ties installed, therefore reducing the restraints and support at the junction where the walls meet the floor.

If you feel that you could be suffering from wall failure as a result of any of the above causes, please give one of our Chartered Surveyors a call now on 020 7935 2502 or email info@blsurveyors.com and we will be happy to assist in any way we can.