Retaining Wall Drainage
BRANZ recommends a minimum of 300mm of clean metal or gravel immediately behind the wall. We lay the first 150mm along the base, sit the perforated coil on top, then cover the coil with another 250mm of.
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Built strong. Built to last.
Engineered Retaining Walls in Christchurch
Top Retaining Walls Christchurch handles the retaining walls that need paperwork. Anything over 1.5m of retained ground, and anything with a driveway, shed, pool or sloping fill above it, needs a chartered professional engineer and a building consent. We run that process and build to the drawings.
- We tell you at the site visit whether you need consent
- Chartered engineer design and producer statements arranged
- We book and meet the council inspections ourselves
- Drainage on every wall300mm of metal, a drain coil and geotextile. Never an optional extra.
- H5 poles as standardThe right treatment for timber that lives in wet ground.
- Consents handledChristchurch City, Selwyn and Waimakariri, start to finish.
- Itemised quotesYou see what the drainage and the spoil actually cost.
Engineered Retaining Walls
Engineered Retaining Walls we build in Christchurch
Schedule 1 of the Building Act sets the line. A wall is exempt from consent when it retains no more than 1.5m of ground and carries no surcharge, which means no vehicles, no buildings and no extra load above it. Cross either of those and you need consent, no matter how small the wall looks.
Christchurch City Council also looks harder at sites with a liquefaction history or a slope hazard, so an eastern suburbs job and a Port Hills job rarely take the same path through consenting. We tell you which one you are on at the site visit, before you commit to anything.
Retaining Wall Building Consent
Schedule 1 of the Building Act 2004 exempts a retaining wall when two things are both true. It retains no more than 1.5m depth of ground, and it does not support any surcharge or any load beyond the.
Read moreRetaining Wall Repairs
The most common by a distance is drainage. Water sits behind the wall, the soil gets heavy, and the wall leans out a little more each winter. Second is rot, where the posts were never H5 or the drainage.
Read moreDriveway Retaining Walls
A retaining wall holds back soil. Add a driveway on top and it now holds back soil plus whatever parks on it, plus the dynamic load of a vehicle moving. A car is well over a tonne. A delivery truck is.
Read moreTiered Retaining Walls
The Schedule 1 exemption applies to a wall retaining 1.5m or less with no surcharge. Two 1.2m walls set far enough apart that neither loads the other are two exempt walls, not one 2.4m wall. MBIE guidance.
Read moreRetaining Wall Cost
These are national guide ranges for walls up to about 1.5m, installed with excavation, drainage and backfill included. Christchurch sits broadly in line with them.
Read morePool Retaining Walls
A pool above a retaining wall is a surcharge, plain and simple, which rules the wall out of the Schedule 1 exemption whatever its height. A wall cut into a slope to make a level pool platform is carrying.
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The part you never see
How we build a retaining wall that drains
Nearly every failed wall we get called to in Christchurch failed the same way. Water sat behind it, the soil got heavy, and the wall leaned out a little more each winter. So we build the drainage first and the face second.
- At least 300mm of clean free draining metal sits behind the wall face
- A perforated drain coil runs the full length at the base
- Geotextile cloth wraps the top and back so silt cannot block it
- The coil discharges to daylight or to stormwater, never a dead end
Where we work
Engineered Retaining Walls across Christchurch and Canterbury
We cover the whole city plus the Selwyn and Waimakariri towns within a sensible drive.
Not sure which wall type suits your section?
We will come out, measure it and tell you straight. The site visit and the written quote are both free.