Damp proof course issues
The extension will straddle two parts of my house. the left-hand-side bit was built in the 1800s and the right-hand side in the 1930s. Initial inspection seems to show that the DPC level lies at a lower level in the new part to the old part. As I definitely want an internal floor without a step I will have to see what impact this might have.
The 'DPC' in the old part of the house behind the external toilet.
Actually, the old part of the house does not have a DPC as is seen in modern homes. The DPC was formed by pouring pitch over the wall which you can see running down the wall. It is also quite high on this side of the house.
It's interesting to note that the outside toilet's DPC (if there is one) is below the one in the main house wall!
The 'DPC' in the old part of the house in font of the toilet
Assuming the DPC runs around the house at the same level it can be assumed to be at this level here, although the air brick is above the DPC on the further side of the house. I'll need to knock away some the render to see the true situation.
The DPC in the 'new' part of the house is a traditional DPC but seems to be a couple of bricks higher than the old house. Where the level changes is currently hidden under the render.
'Tanking' the damp proof membrane to compensate for
different heights of the DPC
A difference in height between the old house and the new extension means that the damp proof membrane needs to extended height up the existing house wall and keyed into the DPC of the existing house at a higher level and covered by plaster.