Extension wall with partial earth

No plans need to be approved as we are doing a building notice.

No planning permission required as it is permitted development.

I am also going to go through these aspects with BCO when they make their first inspection
Sponsored Links
Oh dear. Well enjoy the ride - it might be a little bumpy.

Normally a notice is for those who know what they are doing and have competant dependable builders. I hope you get a helpful and tolerant inspector too, as they do tend to like to check things not design things.
This was originally going to be a self build diy project :D

But succumbed to a deal with the a builder doing all the main parts of the work.

Still keen to do any other aspects of the work myself.

It’s going to be a bumpy ride, and hope to document my experiences for a blog.
Sponsored Links
Hmm, figured we was on a diy forum...
But anyhow it was good hear everyone’s advice on the matter.

Here’s to hoping I have planned everything out sufficiently and I don’t have to end up demolishing anything :D
Well, I was wrong. Seems we needed an engineer to design the wall in the end. Apparently 2 leafs of concrete blocks was insufficient to retain 800mm of Earth.

Engineer ended up designing a 200mm thick reinforced concrete wall.
Hmm? Well building control said yes to this design.

Sheet of mesh on the outside face of concrete and a sheet of mesh on the inside face of concrete, then cavity then inner leaf wall.

First hiccup which cost me £1k...
Yes it won't fall over but some blocks on their side would've been cheaper, heyho maybe £500 spent on some regs drawings would have prudent afterall.
Building Notices are only for use by someone who actually knows what they are doing. Every time.

You've got at least three threads going now. Let's hope it's not £1k a thread.

That wall is way over designed BTW.
That wall is way over designed BTW.

Btw, the wall is also C35 concrete. Along with the my foundations :D

I’m going to be able to build a factory on this site. Or, when my house falls down my extension would still be live and kicking.
Any advice with regards to the tanking detail? My original idea was to apply a coat of DPM paint to the exterior and use a tanking membrane in front of it. This goes up to the DPC on the outer leaf.

BCO have suggested I apply a DPM paint on the cavity side of the outer leaf (in this case the reinforced concrete wall) and also apply a coat on the exterior side. So that if the exterior coat fails, it has a backup of the 2nd coat in the cavity. These get linked to the DPC which is 150mm above the retaining wall. This suggests that in a worst case scenario, the any water will not breach into the cavity.

However tanking specialists have suggested that may not be a good idea as it can possibly cause water to be sitting in the masonry. I should use a single tanking membrane to the exterior side only. Also the suggestion of using both an exterior membrane and a layer of DPM paint is unadvised. However they countered the their advice with, I should stick with what the BCO wants.

Any thoughts?
I wouldn't take the advice of either until I knew exactly what the detail is, Neither of them should be advising.

Besides some bloke on this forum posted a perfectly sensible solution which was completely ignored so I would expect the same approach this time around.

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

Sponsored Links