House performance: 03 Reducing deterioration

Now for "Reducing deterioration."

The standards are fairly loose — any decent builder is normally doing these things. But for Long-Life Quality Housing certification, you have to explain in drawings (to a third party) that the items meet the criteria.

Note: the items below are limited to methods we commonly use, so be aware there are other valid options.

i. Anti-rot and anti-termite for exterior wall framing

Provide a ventilation cavity in the exterior wall, and chemically treat the framing and substrate up to 1 m above ground.

ii. Anti-rot and anti-termite for sill plates

Provide a sill-plate flashing, and use cypress (hinoki) etc. for the sill plate (K3 chemical treatment is also acceptable).

iii. Waterproofing for bathroom and changing room

Use a unit bath (JIS A4416), and use water-resistant gypsum board or water-resistant plywood for the substrate of the changing room walls and floor.

iv. Anti-termite for the ground

Use a slab-on-grade (mat) foundation.

v. Foundation height

Foundation rise from grade ≥ 400 mm.

vi. Moisture and ventilation under the floor

Use perimeter (basement) insulation.

vii. Attic ventilation

Use roof insulation (sealed-roof construction).

viii. Structural members and the like

Comply with the Building Standards Act. (Uses sound materials and rot prevention. Overlaps with above.)

The "deterioration measures" classes go up to Class 3, where the structural framework is expected to last 75+ years.

Notably, this content doesn't touch on deterioration measures for the foundation concrete. To get concrete durability to 75+ years, you have to pay attention to rebar cover thickness and concrete strength — but the standard doesn't address it. A bit of a mystery.