Water – How to do about the rendering & damp-proof course

damp-proof-coursefrench-drainrenderwaterproofing

I have a house that was built around 1890 and is of brick construction with a rendered band running around the base which also forms square edged columns around the front door. Until recently the house had a concrete front garden that met the building at the level of the base of the grille ventilating the ground floor cavity.

I have removed the concrete slab as it was falling toward the building and was, I thought, too high in relation to the ventilation grille. Removing the concrete slab exposed the damp-proof course (DPC) visible at the level of the base of the grille (see images). To be 'belt and braces' I removed the render one course above the DPC and injected Dryzone into the mortar joint.

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My questions are:

  • If I lower the new front garden level to 150 mm below DPC I'm going to be very nearly on top of the brick tier foundation, is this a problem?

  • I want to reinstate the render band as all the other houses have them and it also forms part of the elevation detailing around the front door, but have read that the render shouldn't go past the DPC. If i stopped the render above the DPC and dropped the ground 150 mm I'd be left with a band of fairly tatty looking bricks that have been underground for the last 40 years. How could I finish this without compromising the damp proofing?

  • Should I install a french drain of some kind?

Best Answer

A drop of 150mm would work best if you did it in the summer so that the bricks below the DPC could dry out a bit. If you did it mid winter and another big freeze happened then these bricks could be subject to freezing and surface cracking / erosion. In general - if you do drop the garden by 150mm the bricks below the DPC would benefit from some form of localized rain and wind protection because of the age of the building.

If the garden slopes toward the building or the water table is quite high in your area it would be essential to make sure that any moisture in the garden is diverted away from the building via good drainage such as a French Drain.

There are one or two ways in my experience to tidy up the brickwork below the DPC :

1 : brick slips (slices of new brick) on a fascia with an inch or so of breathing space behind it could be painted to match the building without permanently affecting or altering the original bricks below the DPC. This would still need a bit of venting.

2 : wooden skirting, a bit like an external skirting board (in period with the building) painted to match might be cheaper and easier to install.

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