French farmhouse renovation: Concreting a barn floor

We have a new feast day in our family – Concrete Day.

On July 8, 2020, against all the odds of pandemics and in spite of me not knowing what I was doing, two massive trucks turned up at our house and deposited 10 tonnes of readymade self-levelling concrete – the consistency of pancake mix – into our barn.

It seems so easy, just written out like that, but you wouldn’t believe what it took to get to that point.

Wind back 12 months. My daughter was planning her wedding.

When she looked at the price charged by rural venues in the UK, she said: “Dad, why don’t we do it in our barn?” From such simple questions, DIY epics are born.

“Could do,” I replied nonchalantly. “All we have to do is move out the junk, take some measurements, lay a floor.”

This casual remark turned into the largest DIY job I have undertaken: preparing the way for a concrete slab bigger than the surface area of our London terrace house – 14m by 6m.

Emptying the barn of logs and obsolete gardening equipment was easy. The tough job was digging out the floor, which consisted of 25cm of soil, sand and stones that had accumulated in the 150 years the barn had been in agricultural use.

'I could have hired a digger but the rubbish would have had to go somewhere. So I got the bride and groom to sort and sieve it all'

They gave me dirty looks as they ferried 100-plus barrowfuls all over the garden.

Next job was to measure. I entrusted this to my friend Joël, who also helped me get quotes. Concrete is expensive and every millimetre of depth multiplies the budget.

We decided to make it 10cm thick, but that meant raking small gravel back and forth while one of us was on his knees with a tape measure.

We were advised to mark the top of the hypothetical concrete by driving 25cm rods of twisted iron into the ground. The principle of self-levelling concrete is that it is quick and easy to lay on the day – but you have to be ready.

The technique is to make a container for it with black plastic sheeting. We called this the “swimming pool”. Mostly, the plastic was nailed or taped to the walls but in places we had to support it with sturdy boards held in place by steel brackets.

We were still fiddling with things on the morning of Concrete Day, but at 2pm fate took over. Cement delivery trucks do not hang about: they arrive, they pour, they rinse the tank out. They do not take any left-over concrete with them. You need an overspill area. We did half our porch in an ad hoc fashion.

When the concrete is in, it needs to be “whisked” to expel the trapped air – the company’s sales rep showed us how to do this, and supplied the special tool for the task. Then you wait and watch the miracle of liquid turning solid. When it has dried out, the concrete needs compression joints to stop it cracking as it expands and contracts.

There are plastic strips you can buy for this, but we followed advice and cut 4cm deep grooves in the concrete the length and breadth of the barn with a large angle grinder: it was noisy and dusty but the result was worth it.

As soon as we could, we moved a picnic table and candles into the barn and had a party. In place of the world’s grottiest outside storage area, we have an atmospheric salle des fêtes. And I could not be more pleased.

Which other bride and groom, dressed up to the nines on their wedding day, can tell their guests that they physically laid the floor beneath their dancing feet?

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