How To Dig Postholes

Like most professional archaeologists, one of the first features I learned to dig was a posthole. For posthole nirvana, you just need to follow these five steps.

I remember it like it was yesterday. I wasn’t exactly certain that I was going to stick it out as an archaeologist, so rather than buy a flashy new piece of steel I borrowed a well-used trowel from a friend. Rocking up to site that first day with a trowel worn down to a stub, the Site Director breathed a sigh of relief.

Clearly, I was a safe pair of hands, so he pointed me in the general direction of some amorphous blobs he casually referred to as ‘them postholes,’ and left me to get on with it. It didn’t go well.

We all have to start somewhere, and like most other professional archaeologists, postholes were the first feature I ever learnt to dig on site. But what exactly are they?

Postholes are holes which, in the past, held an upright timber or wooden post – usually as part of a building. They can come in all shapes and sizes – maybe they held a fence post, or the huge central beam of an Iron Age roundhouse. Sometimes they’re filled with packing material, other times they might preserve part of the the post itself. They can be quite shallow (especially if the topsoil has been ploughed), or they can be so deep you can’t quite reach the bottom. And sometimes, they might even hold artefacts that were placed there intentionally, or got mixed in accidentally at the time.

Either way, they’re fascinating things to dig, and forposthole nirvana, you just need to follow these five-steps (as dramatized by digging maestro Dave Britchfield in this short film from our Flag Fen project). Enjoy…

1. Define Define Define

First things first, you need to define the edges of the feature, so vigorously trowel the horizontal surface of the trench until you have a clear circular outline on the posthole. If this is really faint, you may need to score the edge with the point of your trowel, but more than likely you’ll have a clear dark circle (the remnants of the original post) set against the natural clay, chalk or gravel.

2. String it Out (.. or ‘Half Sectioning’)

The most important thing here is to keep your section straight, and no matter how well you think you can do this, dissecting the feature in half with two nails and a string line (otherwise known as ‘half-sectioning’) will give you an edge to work back from.

3. Act natural

What did one side of the feature say to the other? Here comes an archaeologist, just act natural… and therein lies the reason why people over-dig features! The way around this is ‘to work from the known to the unknown.’ Start to remove the soil from the edge of the feature, and chase the cut downwards. Before you know it, the vertical Posthole cut will emerge as you remove the softer fill.

4. Chase the Base

If there are any goodies, you’ll find them in the base. This is where the best dating evidence comes from – a diagnostic pottery sherd, a stone tool, or something precious and accidentally dropped into the base. You may need to take an environmental sample here too (but we’ll save that lesson for another ‘How to dig…!)

5. Plan, Section, Context Sheer and Level

So that was the fun bit… And now come the even ‘funner’ bit: recording! You’re not just going through the motions here – each technique we use is there to help answer a question, so keep this in mind as you’re working. The plan and level will show us how the posthole relates in three dimensions to other features in the trench (was it part of a larger structure, for instance?); the section give us a sense of it’s profile, and how substantial the structure was (a fence line or a building, perhaps?) and the context sheet gives us a clear description of the fill and the shape of the cut (so we can compare and contract with other similar postholes nearby).

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Brendon Wilkins

Written by Brendon Wilkins

Co-founder and Projects Director at DigVentures, Brendon heads up our field and post-ex team. Aside from field archaeology, his specialisms are cheese, tea and writing animatedly about himself in the third person.

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