Macrocarpa Sleeper Retaining Walls in Christchurch
Top Retaining Walls Christchurch builds macrocarpa sleeper retaining walls for people who do not want treated timber in their garden. Macrocarpa has genuine natural durability in its heartwood and no chemical treatment, which makes it the usual choice around vegetable beds and on properties where that matters.
- Naturally durable untreated heartwood
- Chosen where treated pine is not wanted
- Built with treated or steel posts below ground
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It comes with a real trade off and we would rather set the expectation up front. Macrocarpa is durable above ground and much less so in permanent ground contact, so these walls are built with macrocarpa sleepers and posts in something that will survive being buried.
What macrocarpa does well in a garden retaining wall
Heartwood macrocarpa weathers to a warm silver grey rather than the green grey of treated pine, and it looks considerably better doing it. Sections are usually chunkier because it is milled locally from farm trees rather than to a standard, which suits a rustic garden wall.
It is also genuinely untreated, which is the reason most people ask for it. Around raised vegetable beds that is not a small consideration.
The honest limits of untreated timber retaining walls
Ground contact
Buried macrocarpa does not last like H5 pine. We build with H5 treated or galvanised steel posts and macrocarpa sleepers, so the buried component is rated for it and the visible component is the timber you wanted.
Sapwood
Only the heartwood is durable. Boards with a lot of pale sapwood on the edge go long before the rest, so selection at the yard matters and we do not take whatever is on the stack.
Movement
Macrocarpa moves and checks more than treated pine as it dries. On a retaining wall that is cosmetic rather than structural, but it will not stay dead straight.
Macrocarpa retaining wall cost and realistic life
Priced similarly to treated timber walls, sometimes a little above depending on supply, because good heartwood macrocarpa in retaining sections is not always sitting in a yard.
Realistic life with treated or steel posts and proper drainage is fifteen to twenty five years for the sleepers, less if the base sits permanently wet.
Macrocarpa Walls at a glance
- Timber
- Heartwood macrocarpa sleepers, untreated
- Posts
- H5 treated pine or galvanised steel, because buried macrocarpa is not durable
- Appearance
- Weathers to a warm silver grey
- Selection
- Heartwood only, sapwood rejected
- Life
- Fifteen to twenty five years for the sleepers with good drainage
- Best for
- Vegetable beds and gardens where treated timber is not wanted
Macrocarpa Walls in Christchurch: common questions
Is macrocarpa as durable as treated pine?
Above ground the heartwood does well. In permanent ground contact it does not, which is why we use treated or steel posts.
Why does the sapwood matter?
Only heartwood is naturally durable. Sapwood on the edge of a board rots long before the rest.
Will it stay straight?
It moves and checks more than treated pine as it dries. Cosmetically it looks its age, structurally it is fine.
Is it safe around vegetables?
It is untreated timber, which is the usual reason people choose it.
Is macrocarpa safe to use around vegetable gardens?
It is untreated timber, which is the usual reason people ask for it around raised beds. There is no chemical preservative in the sleepers. The posts are the exception, since buried macrocarpa does not last, so we use treated or galvanised steel posts and keep the untreated timber where it is visible and in contact with the growing medium.
Where can you source macrocarpa retaining timber?
Locally, from mills cutting farm grown trees, which is why sections are chunkier and less standardised than treated pine. Supply is variable, and good heartwood in retaining sizes is not always sitting in a yard, so it is worth allowing lead time rather than assuming next week.
Will macrocarpa go grey like treated pine?
It weathers to a warm silver grey rather than the green grey of treated pine, and most people think it looks considerably better doing it. It also checks and moves more as it dries, which is cosmetic on a retaining wall rather than structural.
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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