You Ask, We Answer

We’re technical experts in the complex and ever-changing world of civil and structural engineering design and technical approval.

Can we remove that retaining wall?

Our answer is based on the Link team’s collective experience, which includes involvement in hundreds of projects of varying scales from inception through to construction on site, across the UK over the past 15 years.

Our simple answer is: We’ll try our best.

As part of Link’s involvement in projects, we typically set the highway and finished floor levels (FFL’s) of the proposed development. In undertaking this levels design Link look to achieve the most economical solution for our clients by trying to do the following:

  • Achieve a cut/fill balance where possible to avoid unnecessary cart away (£50 to £200 per m3);
  • Minimise the number and height of retaining walls to reduce cost (£500 to £1,500 per m).

It is important to achieve a cut/fill balance, as by minimising cart away from site, the client shall not only benefit from a cost saving but this shall also offer sustainability, highway safety and disruption benefits. By reducing the number of trips too and from the site by earth moving trucks.

Once the highway levels have been set the FFL’s of the units are typically governed by the gradients set out in Part M of Building Regulations, from the back of highway to the access points into the building. This document is split into three categories:

  • Category 1 – Visitable Dwellings (1:12 for 5m, 1:15 for 10m, steps allowed)
  • Category 2 – Accessible and adaptable dwellings (1:12 for 2m, 1:15 for 5m, no steps)
  • Category 3 – Wheelchair user dwellings (no 1:12, 1:15 for 5m, no steps)

Working to these maximum gradients shall determine the most appropriate FFL based on maintaining the required access gradients to the unit.

Now that the FFL’s are set, the external levels around the units must be designed to tie in with the existing levels on the boundary of the site and the other proposed levels. Typically, an external levels ethos is agreed with the client prior to progressing with this external levels design. Although a gradient of 1:6 is considered acceptable in accordance with Chapter 10.2 of the National House Building Council (NHBC) guidance, a more useable gradient is typically desired. For example, a 2m area at 1:40 before falling/rising at a maximum gradient of 1:15. Once this ethos has been applied the requirements for areas of retaining can be identified. It should be noted that in accordance with Chapter 10.2 of the NHBC guidance a barrier or fence should be provided where the level difference is greater than 600mm, as such it is prudent to try and avoid retaining features in excess of this in areas where there is not already a proposed boundary treatment.

The amount of retaining features within the site can be reduced using some of the following methods:

  • Increase gradients to minimise retained heights;
  • Introduce exposed blockwork/tanking into units or garages;
  • Introduce areas of banking (1:3) within landscaped areas.

If you are looking at a new site and would like a preliminary assessment of the levels within the site, please contact us at and we would be more than happy to provide you with some site specific advice.

Apr 19, 2022