Building near retaining wall

27 Dec 2014
Reaction score
United Kingdom
Hi all,

I'm looking at the feasibility of building a single-storey side extension (marked in red on the sketch) on a property I don't yet own. It would be built well within 3m from neighbours garage and a retaining wall.

I believe the depth of foundations is likely to be an issue, and the presence of the retaining wall is leaving me a little confused.

Which of the following approaches would be correct?

Consider base of retaining wall foundations as foundation depth as side foundation of garage on upper side of wall would be supported by the wall and in turn its foundations.

Consider base of garage foundations as foundations depth.

thanks for reading.

Sponsored Links
You may have to dig the adjacent wall foundation in stages rather in one hit.

Engineers, building control, architects etc, love to put the onus onto the builder regards these little gems. I like to respond with the 'duty of care' statement. :p
Sponsored Links
I once built a garage in the situation of your neighbours garage. Using a 9" fence borer, I dug holes at 4' centres down to a stable level of soil, about 5' on the step side and 2' on the side adjacent to the house. each hole then had 4 vertical rebars in which were bent over to join the rebars that sat in the ring beam (about 18" wide and 6" thick) and innto the over site 4" concrete which also had mesh laid in it. It seemed OK after 25 years.
So in your case I would put in the hole every 3' and 3' deep with a beam across the top of them with the rebars in, on the retaining wall side. Leaving the soil in between the holes should keep everything in place during the construction time.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local