Common questions
Timber retaining walls - common questions.
Straight answers to the things homeowners ask us most often. If your question isn't here, call John - he'll give you a straight answer, not a sales line.
How much does a retaining wall cost in Christchurch?
Every retaining wall is quoted after a site visit - cost moves with wall height (under vs over 1.5m is the biggest break), length, drainage, soil conditions and whether it needs engineered design. A 5m low garden wall under 1m is our cheapest retaining job. A 15m engineered wall over 1.5m with heavy drainage on wet ground is our highest. See the Pricing section above for the full variable list.
Do we need a building consent for our retaining wall?
Walls over 1.5m high need a building consent and structural engineering under the New Zealand Building Code. Walls under 1.5m on a standard residential section usually don't. Walls right on a boundary, or walls retaining a driveway / carrying load, may need a consent regardless of height. We'll check on the site visit and tell you straight up - and if a consent is needed, we handle the drawings, submission, engineering and inspections rather than leave it with you.
Why timber instead of concrete or gabion?
Timber suits most residential retaining - it's cheaper, looks better against a landscape, and can be repaired board-by-board if a section fails. Concrete panels look industrial and are best kept for heavy-duty retaining like driveways or commercial work. Gabion baskets (rock-filled wire cages) look great but are expensive and specialist. We stick to timber because it fits the residential deck-and-landscape work we do anyway. For concrete or gabion walls, we'd point you to a specialist retaining company.
How long will a timber retaining wall last?
Built properly with H5 timber and proper drainage, twenty to thirty years in a typical Canterbury section. Built badly (wrong timber at ground contact, no drainage behind the wall) they fail in five to ten. The difference is almost entirely drainage.
Why does drainage matter so much?
Water is the enemy of a retaining wall. If water builds up behind the wall it pushes the wall forward, saturates the ground so the wall settles, and rots the timber faster. A drainage pipe at the base of the wall with gravel behind the boards relieves that pressure and keeps the timber drier. It's 5-10% of the build cost and probably doubles the wall's life.
How high can you build a timber retaining wall?
Under 1.5m we design and build to standard residential spec. Between 1.5m and 3m we bring in a structural engineer and work to their design. Over 3m is possible but the engineering gets more complex and at that point a specialist retaining company might be a better call - we'll tell you if we think your job suits us or doesn't.
Do you service our suburb?
We build retaining walls across the Christchurch urban area and wider Canterbury - Halswell, Fendalton, Merivale, Redwood, Rolleston, Papanui, St Albans, Prestons, Marshlands, Rangiora, Ravenswood, Casebrook, Harewood, Redcliffs, Sumner, Kaiapoi, Ohoka, Cust, Yaldhurst, West Melton and everywhere in between. We also travel further across Canterbury and the wider South Island for the right job.
Can you build the deck and fence alongside the retaining?
Yes - that's our strongest scope. Coordinated timeline, and the heights and transitions between retaining, deck, fence and landscape all line up because everything is set out together. See our deck building, fence builder, louvre and covered roof and landscaping pages for the rest.
Can you repair or replace an existing retaining wall?
Yes. Panel-by-panel replacement, individual post replacement, or full rebuild - we quote what the wall actually needs, not a full rebuild by default. If only half the posts have failed we replace those half. If the whole wall is compromised we'll tell you and rebuild properly.
