Extension wall with partial earth

[iwanttodiy]

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

 

[^woody^]

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.

 

[iwanttodiy]

This was originally going to be a self build diy project

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.

 

[freddiemercurystwin]

/backs away from thread slowly .......

 

[iwanttodiy]

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

 

[iwanttodiy]

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.

 

[freddiemercurystwin]

Reinforced concrete! WTF! Get another engineer!

 

[iwanttodiy]

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...

 

[freddiemercurystwin]

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.

 

[^woody^]

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.

 

[iwanttodiy]

That wall is way over designed BTW.

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

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.

 

[^woody^]

I'll look you up for when Putin starts to send the missiles over.

 

[iwanttodiy]

I'll look you up for when Putin starts to send the missiles over.

House warming when it’s finally done!?

 

[iwanttodiy]

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?

 

[freddiemercurystwin]

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.