Page 36 - Build 153

more expensive to use. The key is to
ensure the insulation is protected during construction and then protected and kept dry during its service life. The cost of a protection layer is often more expensive than the insulation itself.
● Insulationinthemiddleofthewallisthe most expensive approach. It has fewer moisture and insect problems but is the most di cult to construct.
● Insulationonbothsideshassimilarproblems to the exterior insulation approach with the additional cost of the interior layer.
Always avoid signi cant thermal bridges (see Figure 3).
At construction stage
During construction, ensure:
● theinstallationinstructionsaretohandand
followed
● theworkareaandparticularlyallsurfaces
being waterproofed remain as clean and as
dry as possible
● qualitycontrolismaintainedduring
installation
● completeddamp-proo ngisprotectedfrom
damage before and during back lling.
Damp-proo ng needs consent
There are no solutions given in Acceptable Solution E2/AS1, so all damp-proo ng systems for basement walls need to be submitted for consent as an alternative method.
However, an Acceptable Solution for basement waterproo ng details is given in Appendix A of NZS 4229:2013 Concrete masonry buildings not requiring speci c engineering design.
Repairing existing walls
For existing walls that are letting in water, the options are to:
heat loss
Figure 3
● add surface water interceptor drainage channels around the outer perimeter of the wall if this is possible
● excavate behind the wall, clean and reapply damp-proo ng
● apply a proprietary solution to the inside of the wall (the success rate with such repairs is variable)
Thermal bridge with brick veneer.
● build a new wall on the inside of the existing and incorporate drainage, a sump and a pump within the void space to remove the water coming through the wall.
For more More information on repairing existing leaking basements is given in BRANZ Good Repair Guide Leaking Basement Walls available from www.branz.co.nz/shop.
34 — April/May 2016 — Build 153