For me, the most exciting time in any self-build is the groundworks, when great machines tear open the earth, carving huge slots which will soon become the foundations. It’s exciting because, first and foremost, it’s the start of a new home after what is quite often a protracted period trying to convince planners and others of what you want to build. But it’s also novel because one’s pitting one’s wits against the very ground itself.

Building Control, warranty inspectors, builders and I peer down into each trench, watching every bucketful as it comes up, examining it for content. Is it clay? What sort of clay is it? What will be its bearing capacity? Are there signs of fill, or was there once a pond here? Relief, in most cases, that everything seems to be as expected and turns to renewed activity and preparations for the pouring of the concrete.

The sides of the trench seem at this point to pale into insignificance, their importance relegated to whether or not they’ll stand up long enough for the concrete to be poured. But study those trench walls for they tell so many stories.

First off, in the top vegetable layers, there will be the shards of pottery or those glass bottles that fill the shelves of so many antique shops. I have never yet seen anything built that didn’t yield the seemingly inevitable and ubiquitous willow-pattern china — our forebears must have spent most of their lives smashing the stuff.

Then, deeper down, look out for holes in the trench sides. There may be clean round clay pipes between 50mm and 100mm in diameter. There may just be a patch within the trench wall that seems to weep. There may be a flat stone with two slates or stones leant over to form a triangular shape. These are land drains and when you build on a big site, you realise that the land beneath you may well be criss-crossed with them.

The land on which I’ve just self-built two bungalows had a story to tell below ground. On this sloping site, the top end of the land formed a bank of around two to three metres, against which an old cider press had been built. As we excavated at the lower level, we soon came across a triangular stone culvert (a type of tunnel for water) that ran water at about the same speed as a half-turned-on tap. It was of such quantity and flow that we were able to use it as a source of building water in the inevitable gap between ordering a supply from the local water board and it actually being provided.

We discovered that the culvert ran across what would have been the face of the cider press, where it came to what would originally have been the surface, in an open channel, before disappearing back below ground and into the bank. Where it went was easily answered when we dug the foundations for the lower bungalow and discovered the continuation of the culvert – about 600mm down – running through the boundary hedge and on down the hill between two cottages. Without that culvert, the entire site would have been a quagmire and the two cottages below would have been uninhabitable.

So, if we’d simply poured our concrete, we would have blocked it. Would that have solved the problem? Certainly not; we’d simply have been transferring it. The water wouldn’t have gone away — it would have built up. It could have burst through in a new spring or found its way around the new foundations to reappear on the surface and flood the lower bungalow. Ultimately it could have flowed around and impacted on the cottages below. Perhaps, most alarmingly, over time it could have saturated the soils surrounding the foundations and caused settlement. Those guys a couple of hundred years beforehand knew what they were doing, and the site deserved our respect for their labours. So we picked up the culvert and, using modern methods of a stone-filled trench with perforated flexible pipe, diverted the stream around both bungalows and connected it to the outfall it had always had.

The land beneath us all has been tamed from nature by preceding generations, and there were no greater masters of it than the Victorians. Our major cities and towns were largely shaped by them. We admire the town halls, police and railway stations that they built. We marvel at the Houses of Parliament, the bridges, the railways and waterways — all of which were dug out by hand.

However, those structures are not their greatest legacy — what lies beneath, the miles upon miles of sewers and culverts are the true gift, without which those same cities and towns simply wouldn’t function.

We now just accept their presence. Yet no one seems to take on responsibility when gullies fill, drains block or culverts collapse. “They’re old,” is all that’s said. “They’re not fit for purpose.” But they weren’t designed to hold discarded supermarket trolleys or other such debris thrust within them. Nor was it envisaged that the corbelled brickwork would have to support 44-tonne axle loads. These things that we don’t see and seem all too happy to ignore are a wonder and they shape our landscape. Their replacement, if they continue to be degraded, would be prohibitively expensive, and ignorance of their purpose could defeat all our best endeavours.

The land beneath your proposed self-build most likely has its own story to tell. So proceed with caution, and take a good look down the trenches before you accidently obliterate history and the clever designs of our ancestors.

 

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