Enlarging my crawl space - Party Wall Act


I’m hoping to deepen my crawl space for a number of reasons, primarily easier access as its only 300mm and also to encapsulate it.

My question is with the Party Wall Act. So with section 28 below, do I need to advise my neighbour regardless or only if I’m going further than the foundations which isn’t my intention. If the inspection pit shows I would need to go beyond the foundations then surveyor will be called in. (Cost of under pinning will probs shelve the idea anyway)
28 What does the Act say if I want to excavate near neighbouring buildings?
If you plan to:
 excavate, or excavate for and construct foundations for a new building or structure, within 3 metres of any part of a neighbouring owner’s building or structure, where any part of that work will go deeper than the neighbour’s foundations.
Thanks in advance for you time and help.


Hi Brian. I’m sorry I can’t help with the Party Wall Act but I can’t help being curious (nosy!) about the intent. It seems like a lot of work to insulate the floor. The safest (i.e .safest for integrity of the building, minimising risk from moisture etc…) is usually to remove a wooden floor and install an insulated solid floor. If you’re going to be lifting the floor to excavate, then you may as well either put in a solid floor or insulate the timber floor from above. When you say encapsulate I think that means using foam - is that correct. I’m still learning and interested to understand different situations that can arise. Cheers. Chris.

Hi Chris
No problem and thanks for showing an interest in my post.

If I can enlarge the crawl space I hope to run some services from there and ducting for a heat pump. I want to utilise the chimney breast as a service duct to run utilities from the crawl space to each floor.

To encapsulate is to insulate and water proof the area with a vapour barrier, I’ve added photos



Wow - thats a project with huge ambition. Sorry I can’t help. I’ll be interested to learn more so please share as you go along.

No worries Chris. I certainly will. Thanks again.

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Just for anyone wanting to know the answer, it is only if I dig below the foundations will I have to advise my neighbour. Hopefully the test put will be good news.

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I’m curious. Any updates on this?

I have a small, useless, crawl space and following AECB advice an thinking of tanking it and filling the void with insulation with a floating floor above.