Methods of damp proof course installation in construction.
Damp proof course above internal floor level.
As it dries out the damp retreats slowly back to the points of ingress so if you are not able to see any isolated damp areas either ventilate and heat or shut all the doors and windows and use a dehumidifier.
Damp below damp proof course level.
Damp proofing is defined by the american society for testing and materials astm as a material that resists the passage of water with no hydrostatic pressure.
Tip 1 if a concrete floor is damp all over it is hard to isolate the moisture source.
The below diagram shows what bridging of the damp proof course looks like.
Dpc material for cavity walls.
Where it is not possible to insert a damp proof course 150 mm above the external ground level for example if the building has a solid external wall and the internal floor level is less than 150 mm above the external ground level external drainage solutions may be necessary such as the installation of a french drain.
By simply lowering external ground levels this will allow wall base evaporation to help control rising dampness.
Houses are usually built with a damp proof course dpc just above floor level to prevent moisture rising up but if this has failed or the property did not have a dpc then rising damp can occur.
Waterproof is defined by the astm as a treatment that resists the passage of water under pressure.
Depending on the extent of the rising damp this can be a more costly and extensive job to repair.
A quick summary checklist.
Types of materials for damp proof course.
Dpc material for situations where differential thermal movements occur.
Rising damp usually occurs in masonry walls because of the failure or absence of a damp proof course although poor sub floor ventilation and bad site drainage can also be contributors.
Dpc above ground level.
Dpc material for floors roofs etc.