Jack and Pack: How a House Gets Re-levelled
If a house has started to feel like a fairground ride, with doors that stick and floors that slope, the usual fix is a method builders call jack and pack. It is one of the most common timber-floor repairs in New Zealand, and getting it right matters just as much as deciding to do it.
What jack and pack actually means
Timber floors sit on bearers, which sit on piles. Over time, piles can settle, rot, or shift in an earthquake, and the floor above goes out of level. Jack and pack is the process of lifting the floor back up with hydraulic jacks, then fitting timber packers between the pile and the bearer to hold it at the new, level height.
How the work is done
Guidance from Building Performance (part of MBIE) and BRANZ sets out the general sequence:
- Check the floor structure first. Any pile that is loose on its footing, or leaning more than about 15mm off plumb, should be replaced rather than packed. The rule of thumb in the official guidance is blunt: when in doubt about one pile, it is usually fine to leave it; when more than one is in doubt, replace them.
- Lift evenly. Jacks sit on flat timber blocks, never on a lean, and go in under load-bearing walls first. The floor is raised gradually in small, even increments rather than cranked up on one jack at a time.
- Pack with treated timber. Packers should be a minimum of H3.2 treated timber, cut to match the bearer and pile, with any cut ends resealed. A single solid packer is used rather than stacking several thinner pieces, and a damp-proof course goes under the packer where required.
- Fix piles properly. Concrete piles are tied to the bearer with galvanised wire pulled tight; timber piles are strapped with galvanised or stainless steel fixings, with stainless required on piles under 600mm high. New piles go into their own hole next to the old one, set in concrete on firm ground.
- Check the cracks. Once the floor is back level, any foundation cracks wider than 1mm are filled as part of the repair.
Common mistakes
The published guidance flags the same few errors again and again: lifting unevenly or over-lifting one jack, leaving loose or leaning piles in place instead of replacing them, using untreated timber for packers, and skipping the damp-proof course. Each of these can leave a floor level today but in trouble again within a few years.
Do you need a building consent?
This is the part worth checking before work starts. MBIE's exempt building work rules (Schedule 1 of the Building Act) allow general repair and replacement of a building element without a consent, but only where a comparable product goes back in the same position and the work is not a substantial replacement of a structural element. Swapping a handful of rotten piles for new treated ones in the same spots can fall within that exemption. A larger re-level involving many piles, or any sign that the subfloor framing or bracing needs more than a like-for-like repair, moves into territory where a consent, and an engineer's input, is the safer path. If there is any doubt, check with your local council or get a professional opinion before you start.
Safety note
Under-floor spaces are treated as confined spaces in the official guidance: tell someone where you are working, check that power and gas lines nearby are safe, and have a plan if something goes wrong.
This is general information, not a substitute for site-specific engineering advice. Every house and every site is different, and a professional should assess your particular situation before any re-levelling work begins.
If your floor is sloping or your piles look like they need attention, get in touch with Fil Engineers for an assessment.
