New Built Garage – Two System Waterproofing
The Damptec team worked on this NHBC warranty site where a new build garage required two systems of waterproofing.
We provided the specification for a combined system with third party warranty:
- Type A External Barrier Protection and Type C Drained protection
The waterproofing solution determined is defined in BS 8102 2022 Protection of Structures against Water from the Ground as a “Grade 2” environment where no water penetration is acceptable.
It is worth noting that major third part warranty providers such as NHBC, Premier Guarantees and LABC have insisted for some time on the installation of combined protection as a fundamental condition of their warranty. They also require that a CSSW qualified waterproofing design specialist be involved at the design stage.
Our Specification
WATERPROOFING TYPE “A”:
External: Combined Waterproofing
Primary resistance of the structure was provided by Koster bitumen-based waterproofing on the positive side:
- Application of Koster Polysil TG500 primer to all surfaces in a spray coat application.
- Application of two coats of Koster Deuxan-2C polymer modified thick bitumen compound at 6kg/m². 1st coat to be applied with a 6mm notch trowel and then levelled. Following the installation of glass fibre mesh a second coat is applied with a 6mm notched trowel to a total wet film thickness of 6mm and finished level.
- Once the Deuxan had cured (following day depending on air temperature), we mechanically fixed Delta-Geodrain Quattro membrane, with joints overlapped and sealed. The double drain relieves hydrostatic pressure build up and provides additional factor of safety. REF: BS 8102: 2022, Item 6.4 sub-surface drainage.
WATER PROOFING TYPE “C”
Internal: Type C (Drained) protection
Secondary protection, which manages any water ingress which occurs as a consequence of an installation defect, was provided by a cavity drain membrane system.
Wall Cavity Drain Membranes
Walls: We mechanically fixed 8mm membrane to the internal side of the external cavity.
- A fillet was formed along the wall/floor junction using repair mortar.
- The wall membrane was installed from base of wall up to DPC level.
- DPM was taped to the wall membrane with Waterseal Tape overhanging the engineering bricks.
Damp Proofing the Beam and Block Floor
- We taped the DPC to the Delta MS 500 membrane installed over the concrete beam and block floor.
