Retaining wall basics

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

Rebuilding Block retaining wall

Submitted 3 years 7 months ago

Hi. My some has a property on Nottingham, and needs to rebuild a retaining wall in his rear garden, about 8’ from the rear of the property, where the land drops by about 1.8/2.0m into his small garden.
Is there anyone who can recommend a competent brick/block layer to do this work correctly, and include drainage through and behind the wall. The wall seems to be constructed of single course dense concrete block at present... thank you fir your assistance

Reply

Submitted 3 years 7 months ago

Hello there - thanks for leaving your comment.

I'm afraid we're unable to recommend tradespeople but your local authority building control team may be able to give you some guidance. You can find their details by entering your postcode into the postcode search at the top of this page.

Kind regards
Julie, LABC

Does a retaining wall *require* drain holes?

Submitted 3 years 7 months ago

I have a very long (about 21m / 70 feet) by 5 feet high wall across the back of my property which has no weep holes whatsoever. I have become very concerned that it could collapse due to water retention behind it, but the builder assures me that this could not happen - even though the upper ground is very waterlogged. Am I being unreasonable by insisting on having drain holes drilled? If they should be present, what sort of frequency would you expect? (i.e. how far apart would they need to be?)

Footing

Submitted 3 years 6 months ago

Hi there
I have a garden which is tiered to the back by 2ft in height.
It had a shoddy retaining brick wall with inadequate footing which consisted of a 2 inch mortar bed and as a result has failed.
I’m in the process of taking down the wall and cleaning off the bricks to rebuild, what depth footing would you recommend for a wall of this small size?

Retaining Wall Guarding

Submitted 3 years 6 months ago

Hi, the retaining walls in my garden are causing me concern, The height is over 600mm and it was not supplied with any safety guarding. Do you know of a building regulation that may cover this ?

Retaining wall fear it might collapse

Submitted 3 years 5 months ago

My neighbours retaining wall has no motor between breeze locks .was covered in ivy, since I have removed ivy, does not look safe. Have been onto my council building control, because of when it was built no warrant needed. What can I do to make him repair this. My oil tank is right in front of this wall.

UNILOG retaining wall

Submitted 3 years 5 months ago

Good afternoon, Do the LABC cover bespoke timber retaining walls such as UNILOG?

Reply

Submitted 3 years 4 months ago

Hello there - thanks for getting in touch.

If you propose to undertake a retaining wall as part of any building work covered by the building regulations we would always recommend that you seek appropriate professional advice from a suitably qualified structural engineer who will be able to advise regarding bespoke solutions.

Kind regards
Martin, LABC

Distances from House Retaining Wall

Submitted 3 years 4 months ago

What is the minimumRequired distance from a house situaated downhill when constructing a retaining wall

Existing wall

Submitted 3 years 4 months ago

I have a 5ft high 200mm wide wall retaining heavy clay soil. I’d like to put a log cabin on the retained soil, weighing around 800kg over 12sq m floor. How close to the wall can I put it without risking damage from the extra weight of the cabin?

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