Retaining wall basics

06.06.2016
Blog Post
Picture showing a retaining wall

Retaining walls can be tricky to build as they need to be strong enough to resist horizontal soil pressure where there are differing ground levels.

One of the things you must get right is the thickness of the wall. It should be at least 215mm thick and bonded or made of two separate brick skins tied together.

This should be enough in most cases with minimal water pressure or where the ground level difference is less than a metre.

You also need to consider the effect of ground water, which can create huge pressure on the wall and soak the brickwork if allowed to accumulate behind. Create a way out for the water by adding a gravel trench and pipes through the wall.

If not properly constructed, water can also penetrate the brickwork structure from above through the mortar joints, affecting the long-term durability of the retaining wall. So add brick copings, which must always be F2, S2 (frost-resistant low soluble salts), with an overhang and drip groove to minimise water damage.

Important points about retaining walls

  • Don't forget to include movement joints in the wall and use piers on either side to increase strength at the movement joint position.
  • If you're using two separate brick skins in stretcher bond, you have to provide reinforcement by tying them together. Use stainless steel bed-joint reinforcement every third course to boost the strength.
  • Use a high-bond damp proof course below the capping/coping and sandwich the DPC in mortar.
  • Waterproof the retaining side of the wall and allow water to drain away from this side through weep holes/pipes.
  • Slope paving away from the wall and provide gravel drainage strips where possible.
  • Don't forget to protect waterproofing from damage while you’re building.
  • Don't build higher than one metre without involving a structural engineer.

Want to find out more about this type of work? Visit these links:

 

Please Note: Every care was taken to ensure the information was correct at the time of publication. Any written guidance provided does not replace the user’s professional judgement. It is the responsibility of the dutyholder or person carrying out the work to ensure compliance with relevant building regulations or applicable technical standards.

Comments

(No subject)

Submitted 3 years 9 months ago

I have been retired for several years but still find it useful to be kept informed on innovations and new ideas.

(No subject)

Submitted 3 years 9 months ago

My next door neighbour has built a large extension this has required the removal of soil next to our property. There is a 1m+ vertical wall of soil along our property line. We have received no notification of the removal of this soil or the of proposed retaining wall construction. Along the property line on our side we have a open sided veranda, a small brick and concrete platform on which stands a Gas BBQ and a 200L water butt which collects rainwater from the veranda. I have a strong suspicion our neighbour intends to shore up the soil with timber. This will be totally inadequate and prone to collapse within a short period of time. I would appreciate your guidance and any further information on how to proceed. I have a copy of The Party Wall Act 1996 but there is nothing in there covering this type of situation. Many thanks for any input.
Patrick

Reply

Submitted 3 years 9 months ago

Hello there

If you can email me at julie.mcnamee@labc.co.uk we'll send you a reply by email. The answer is quite long and involved.

Many thanks,
Julie

(No subject)

Submitted 3 years 9 months ago

Hi could you tell me how close can a building be put to a retaining wall it is about 10 feet at the highest point yours Tom Rolfe thank you

Reply

Submitted 3 years 9 months ago

Hi Tom

Thanks for your enquiry.

In general terms there is no minimum distance that someone can build from a retaining wall. In many situations a retaining wall may form the line of the building itself.

Is it your wall or one to a neighbouring property?

If you're intending to build near to the neighbour's wall, the Part Wall Act may apply. Here's a link to an explanatory guide: https://bit.ly/2JHCzqW

In your particular situation you will need to ascertain what the condition of the wall and its foundations are. As it is 10 feet tall you may wish to employ an engineer or surveyor to advise on the condition of the wall and how your build may impact on it.

Many thanks,

John, LABC

(No subject)

Submitted 3 years 9 months ago

I have a newbuild property purchased 4 1/2 years ago. The houses immediately behind, also constructed at the same time by the same builder, are on a higher level.
I have in my garden, constructed by the builders, a retaining wall built entirely of round timber posts set in concrete 94cm (plus what is below ground) x 100mm. These posts retain a vertical earth bank leading to the rear property party fences, which are approximately 12 feet in height above the general ground level of my garden and 3 feet behind the vertical earth bank.

The retaining posts for the most part are completely rotten and can be crumbled away by hand, after only 4 1/2 years. When they collapse as they will, the earth bank will also collapse when it becomes saturated after heavy rain. That will then threaten the fencing between my property and the two neighbouring properties backing onto mine, not to say the stability of parts of their own gardens.

To employ a contractor to remove the posts and replace will cost a considerable amount of money. I expect structural posts of this nature to last a considerable time more than I have stated and therefore the posts would certainly seem not fit for purpose.

I do not seem able to find out whether or not this structural defect is covered by my LABC guarantee and I wonder if you would be kind enough to advise me about this and also let me have any other observations you might have on the problem.


Many thanks

Reply

Submitted 3 years 9 months ago

Hello there

You should contact LABC Warranty about this - you'll find their contact details here: https://www.labcwarranty.co.uk/get-in-touch/

Many thanks,
Julie

Webmaster note

Submitted 3 years 9 months ago

All comments posted at an earlier date to this one have been transferred from our old website.

New home retaining wall

Submitted 3 years 9 months ago

I am in the process of buying a newly built home and in the rear garden when I first looked at this home it was wooden to a height of 6 foot on the boundaries i.e side fences left and right and a fence across the bottom of the fence.
The building company have now removed the wooden fence across the bottom of my garden and have built a approx. 3 foot retaining wall because they say the wooden fence will not retain the ground on the opposite of my fence at the bottom of the garden and there needs to be a pathway for houses at the rear of for access. Because of this they are also saying that they will add a 6 foot wooden fence on top of the 3 foot retaining wall because of privacy in my garden, this will look out of line with the height of the side fences and look totally silly, can you advise what can I do please.

Reply

Submitted 3 years 9 months ago

Hello there

Thanks for the enquiry.

Although garden fences are not usually controlled under the Building Regulations you may wish to check with your Local Planning Authority as a fence above 1m adjacent to a highway or 2m elsewhere would need Planning Permission. You'll find information about this on the Planning Portal: https://bit.ly/2G6Q7KZ

Thanks, John

Add new comment

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Sign up to the building bulletin newsletter

Over 48,000 construction professionals have already signed up for the LABC Building Bulletin.

Join them and receive useful tips, practical technical information and industry news by email once every 6 weeks.

Subscribe to the Building Bulletin