The first slab came up at 8.40am on Saturday with a noise like a very large biscuit breaking. Underneath it was one confused worm, a scrap of blue plastic and a layer of black, soaking sand. That was the moment our damp front wall stopped being a mystery and turned into a ground-level problem. By lunchtime we had a trench, a heap of soil taller than the gate and Maureen at her window with the expression of a magistrate.
A spade against £3,800
A quick recap for anyone who missed the saga. Our survey flagged high damp readings at the base of the front room wall, and in April a damp-proofing company's "free survey" ended with a quote of £3,800 for injected damp-proofing and replastering. In early May we paid an independent surveyor £250 to look instead, and he found something duller and far cheaper.
Over the years the path and the flower bed beside the front door had been built up until they sat higher than the damp-proof course, the thin waterproof layer in the brickwork that is meant to stop ground moisture climbing the wall. Somebody had also rendered a band of cement along the bottom of the wall, and the render ran straight across the course like a little bridge. "Your damp-proof course is probably fine," he said. "The soil's just on the wrong side of it." What he told us to do was lower the ground to about 150 mm below the course, cut the bottom off the render and let the wall dry out before spending anything serious.
Saturday 31 May: the digging
We lifted the six slabs nearest the wall and stacked them against the gate. Matt strung a line along the brickwork at the height of the damp-proof course, which we found by looking for a thin dark seam in the mortar, and then hung a spirit level off a nail so every spadeful could be checked against it. Two of us, one wheelbarrow, one trench about 40 cm wide and 5 m long. The gas meter box is on that same front wall and the supply comes up beside it, so we stopped well short and finished that corner with a trowel and a head torch.
By one o'clock we had moved fourteen barrowloads and I had lost the feeling in my left thumb. Kev turned up at half past with the trailer and looked at the heap for a while. "That's a lot of dirt for a damp patch," he said, and then took two loads to the tip while I put the kettle on.
Sunday 1 June: the render, the gravel and a mistake
The render was the loud part. With a bolster chisel, a club hammer, safety glasses and a dust mask, Matt took the bottom 30 cm of it off in plates. The brick behind was dark and cold, with a white bloom of salts on it.
Then came weed membrane against the soil, a strip of gravel about 40 cm wide along the foot of the wall, and the slabs back down on a bed of sharp sand. We laid the first two and admired them. Then Matt checked them with the level and a 7 mm offcut, the slight fall away from the house the surveyor had asked for, and the bubble told us we had laid them sloping towards the wall. We had built a lovely new channel to drain the rain at the very bricks we were trying to dry. We lifted them and relaid the lot in the last of the light, and nobody said anything for about twenty minutes, loudly.
The whole job cost £85: a tonne bag of gravel £58, sharp sand £9, weed membrane £11 and a bolster chisel £7. We used about half the gravel, because the smallest bag the supplier would deliver was a tonne. The rest sat by the gate for a week while Maureen asked twice whether it was staying. What I'd change is simple: mark the fall on the first slab with the level before the sand goes anywhere near it.
What the readings said
The surveyor had pencilled three crosses on the front room wall, at 15, 30 and 60 cm above the floor, and Jas lent us his pin meter so we could check them ourselves. The scale is only good for comparing a wall with itself, the surveyor said, because salts in old plaster make it read high. In April the lowest cross read 26. In early May it read 25. On Monday evening, a day after the last slab went down, it read 23.
Two points on a meter could be the weather, the meter or hope. The surveyor was clear that a wall which took decades to get wet will not dry in a weekend, and that we should think in months. Pickle, kept indoors for another ten days, watched the whole operation from the front room windowsill and seemed to approve of the gravel. I'll take the next reading on 1 July and write down whatever it says, whichever way it goes.
