Piled foundations – gap between pile and bearer

Cause

Timber shrinkage due to use of green (wet) timber during construction

Repair

  • Support the bearer with jacks and insert a minimum H3.2-treated timber packer the full width of the pile. Fix in place with 100 x 3.75 mm nails. Nails should be hot-dip galvanised, or stainless steel in exposure zone D, or in zones B and C where the top of the timber pile is less than 600 mm from the ground

  • piles less than 150 mm high require DPC (damp-proof course) under the packers

  • where the gap between pile and bearer is greater than 100 mm the pile should be replaced.

Cause

Pile has rotted

Repair

  • you can check for rot in timber piles or other timber with a screwdriver. Try to push it into the timber, and if the screwdriver easily enters the timber, then the timber is rotten

  • all rotten piles should be replaced, following Section 6 of NZS 3604:2011 Timber-framed houses. Use H5 treated timber piles (or precast concrete piles). Replacing just a few old rotten wooden piles under a house with new treated timber piles in the same positions does not require building consent (but still needs to comply with the Building Code). If you get a contractor to do the job, repiling falls into the category of ‘restricted building work’ and must be carried out or supervised by a licensed building practitioner with a Foundations licence. Total or extensive repiling will require building consent.

Cause

Pile has sunk into soft ground

Repair

  • Repiling is required, as in the repair above for rotten piles, but the excavation for the pile must go down to good ground.