Widening garage by building directly on top of 5ft stone wall (boundary)

23 Jun 2018
Reaction score
United Kingdom
Hi all,

I would like to extend my garage in width by approximately 0.8m to add much needed storage space inside. This extension would only be on one side of the garage, extending on top of the stone boundary wall that separates my elevated land from the neighbours.

I have written agreement from the neighbours that they absolutely agree for us to do this as we get along great.

Currently you can see below that my garage has an unused area to the left hand side of it (see below pic). This unused area is approximately 1.5m when measured from the outer brick wall of the garage to the outer edge of the stone that the boundary wall is constructed from.

thumbnail_IMG_20190901_193039.jpg thumbnail_IMG_20190901_193100.jpg thumbnail_IMG_20190901_193105.jpg

The boundary wall is an extremely solid stone wall around 5ft high. Basically my drive and garage stand 5ft higher than the neighbours.

For me to build directly on top of the existing stone, my thoughts were drilling down into the stone wall at multiple points along the full distance and knocking 20mm steel rod into the top of the stone acting like a dowel, then laying concrete blocks on top of the steel rod and concreting the bottom course in, to act as a strong 'foundation' as such. Once this was done, I would pour regular concrete to form the floor which would be to the right hand side of the bottom course which will re-enforce the bottom course that are also steel doweled.

After this the plan was to just lay blocks in the regular fashion whilst double skinning every 2m back to give vertical support.

Can anyone offer advice on the above, is there any better ways to do it?

Thanks in advance,
Last edited:
Sponsored Links
Basically you want to build right up to the boundary edge (bad idea), adding another say nine vertical feet onto a wall that is already five feet high, without any clue as to what the original wall is built upon? Couple that with the fact that a new neighbour may want to build up to his boundary only to find the neighbours roof (gutter, fascia etc) overhangs his property and that he risks undermining foundations that (may or may not) be just below the surface of his ground.

As well as that, you claim to be gaining 1.5 meters? I think you need a new tape measure. I'm seeing about 700-800mm at best.
It would need the stone wall removing, new foundation and new garage wall.

Nice easy job to do with great access (n)(n)

On a serious note -you really cant build off the existing garden wall which has unknown stability.
Sponsored Links
Thank you for the replies. A much bigger job than originally thought. The distance is just over 0.8m not 1.5m as originally wrote, for some reason I had 1.5 in my mind!

Probably not worth the hassle or expense as it'll be a few thousand at least...

Time to think of other ways to utilize the area!

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