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Seeking structural engineer advice


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Hello, we’re building an extension, the retaining walls are up and now the builders are laying down the brickwork for the house. The problem is that it is starting to look like two rectangles, one inside the other at completely different angles. I have attached some photos for a slightly better picture. 01472234-9361-4AB3-B044-B8669544D087.thumb.jpeg.8fad6f1bc45188063df02b6c89f2c73e.jpeg



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Interesting photographs. There is a saying that if something does not look right it probably isn't. So I think you're right to query.


Get some professional advice if you are not getting this at the moment. From what I can from the few photo's see the excavation may not be safe.


Setting aside the geometry - blockwork setting out, as others have touched on this.


The photos show a line of trees close to the excavation, you have a big "dumpling" of soil left in the middle and thus it seems like you are not doing a basement? Also, there seems to be no reinforcement in the hollow block walls etc. So it looks like a deep underbuilding to some extent.


What you have seems to suggest that someone has designed this to comply with the NHBC guidelines on foundations near trees, hence the depth of what looks like a strip foundation. The thing is that these are guidelines. The key here is to look at the layers of soil. Tree roots seek out nutrients and water, once they find that they follow that strata.


Often, with a bit of pragmatism you can make a case for not going down so deep. You need to look at the layers of soil and see where the roots will go, then describe this and make the case for the correct foundation depth.. thus the most cost effective option.


The photos show that the wall is pretty close in places to the edge of the excavation, so not much room for a "clay board etc - compressible / void forming type material" which in layman's terms is a piece of soft material that allows the ground to swell and shrink without applying significant pressure to the side of the wall. Your excavation has what looks like a good "stand up time" that roughly means that you can dig a hole and the excavation will stay stable for a certain amount of time before it starts to collapse into the hole.


How you measure stand up time is based on geotechnics and experience. It looks from the photos that someone has made the right (lucky call) and just dug the hole wide enough to get the found in without propping - thus, with hind sight the stand up time (so far) has been enough to get the outer leaf of wall in before the soil moves..for now. However, it also looks to me that perhaps someone has dodged a bullet in that if an excavation that size collapses there could be a serious accident.. ? The thing to watch out for is that if the soil now moves the single outer skin will probably collapse with it. You may be on borrowed time. Be safe first and foremost.


What you have is interesting, so if you can, post some drawings of what is required, also, if you have any structural calculations post these too. Would be interested to see how this all works.


Look after yourself and others. Again get some professional advice as from what I can see the excavation may not be safe.. it will serve you well.


Al the best.




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