Pole and Rail Retaining Walls in Christchurch
Top Retaining Walls Christchurch builds pole and rail retaining walls, using round treated poles set in concrete with horizontal timber rails fixed behind them. It is the simplest form of timber retaining and on the right site it is also the most economical.
- Round H5 poles with horizontal timber rails
- Suits rural, lifestyle and informal settings
- The most economical way to retain a long bank
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Round poles are stronger than a sawn post of the same nominal size, because there is no grain run out at the corners, and they take treatment well right through. On a lifestyle block, a farm track cutting or an informal garden bank they look correct in a way a machined sleeper wall does not.
Where a pole and rail retaining wall earns its place
Long rural runs where the wall is functional rather than decorative. Bank stabilisation along a drive. Terracing on a lifestyle block. Anywhere the setting is informal and the budget matters more than a crisp line.
Because the poles do all the work and the rails just span between them, it is quick to build and easy to extend or repair one section at a time.
Building pole and rail retaining walls properly
H5 poles, concreted
Ground contact means H5, and the pole goes into a concrete surround with embedment matched to the retained height. On a pole wall there is no redundancy, so a marginal post is the whole wall.
Rails on the retained side
Rails sit against the poles on the retained side so soil pressure pushes them onto the poles rather than off them, fixed with galvanised coach screws or bolts. Fixing rails on the outside is a common mistake and it puts the entire load through the fasteners.
Backing and drainage
Geotextile behind the rails so soil does not wash through the gaps, drainage metal, and a pipe at the base like any other wall.
Pole and rail retaining wall cost and what you give up
The cheapest way to retain a bank properly, generally at the bottom of the timber range at roughly $160 to $420 per lineal metre depending on height and pole spacing.
What you give up is precision. Round poles are not uniform, so the line has a slight irregularity. On a rural boundary that is charm. On a Fendalton front boundary it is not, and we would suggest sleepers instead.
Pole and Rail Walls at a glance
- Poles
- Round H5 treated, concreted in, embedment matched to height
- Rails
- Fixed on the retained side so pressure holds them on
- Backing
- Geotextile, drainage metal and a base pipe
- Cost
- About $160 to $420 per lineal metre
- Best for
- Rural boundaries, lifestyle blocks, informal banks
- Trade off
- Slight irregularity in the line, poles are not uniform
Pole and Rail Walls in Christchurch: common questions
Are round poles stronger than square posts?
For the same nominal size generally yes, because there is no grain run out at the corners and treatment penetrates well.
Why do the rails go on the inside?
So the soil pressure pushes them against the poles. Fixed on the outside the whole load goes through the fasteners.
Is it suitable for a suburban front boundary?
It can be, but the line is less precise than sleepers. In a formal street setting we would usually suggest sleepers or concrete.
Can it be repaired in sections?
Yes, easily. One pole or a run of rails can be replaced without touching the rest.
What size poles are used in a pole and rail wall?
Diameter is set by the retained height and the pole spacing rather than by preference. Round poles carry more bending than a sawn post of similar nominal size, because there is no grain run out at the corners, which is part of why they suit long rural runs where fewer, stronger posts beat more, weaker ones.
Can rails be replaced without removing the poles?
Yes, easily, and it is one of the main advantages of the system. Rails are fixed to the face of the poles on the retained side, so a failed rail unbolts and a new one goes on without touching the structural part of the wall.
Is pole and rail suitable for a house boundary?
It can be, though the line is less precise than sleepers because round poles are not uniform. On a rural or lifestyle boundary that irregularity reads as character. On a formal suburban street frontage it usually does not, and sleepers or concrete are the better call.
Recent Christchurch jobs
Boundary wall between us and the neighbour on a new build. Sorted the levels, the consent question and the fence on top in one job. Turned up when they said and left the site clean every night.
Builder here. I use them on subdivision work because the paperwork comes back complete. PS1 up front, PS4 at the end, no chasing.
Wall failed after the big rain and took part of the bank with it. Made safe within two days and rebuilt a month later with real drainage behind it.
Terraced the back lawn into two levels. Fast, tidy, fair price, and the drainage was done properly.
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