How can I put a row of 5' round posts into the ground as close as possible and keeping them parallel?
Question:I am trying to make a 'wall' of wooden posts up against a 'cliff' of clay soil as part of a garden feature. I hope they will act like a gamion keeping the clay soil from falling onto the lower terrace where our seating is planned. However, trying to keep the 5' posts not only straight and perpendicular but also as close together as possible so they almost touch is proving very difficult. The poles are 5' and it is hoped that they will be at least 1.5 feet into the ground. I am about to try putting in post number 1, leave a post width and then put in post number 3 etc and then after reaching the end go back and put in the 'missing' posts in the hope that they will all stay parallel. However, your suggestions would be most welcome!
Answers:
It sounds like you want the posts to act as a retaining wall. This is definitely possible.
Since you want the posts right next to each other, almost touching, my suggestion would be to dig a trench first. You can use a trenching shovel, or you can use a trenching machine available for rent.
Then set up a string line, just a string stretched out and tied to two stakes, along the line where you want the wall to be, so the posts will all be in a straight line. You might want to put the posts into concrete so that they remain straight up and down. Put the posts in, one right next to the other, posts #123456, etc. and have them just line up with your string line. I would not do odd number posts then go back to put in the even number posts. Use a level vertically against each post to ensure each one is perpendicular to the ground.
Once you've got your posts in and the concrete has set, then backfill by putting the soil you took out of the trench behind the posts.
Good luck on your project.
You need a trench 1.5 feet deep and the width of the posts. Put all the posts in and tie them at the top while you backfill the trench.
You could try attaching the posts to horizontal pressure-treated boards hidden behind them (probably one high, the other towards the base). This would keep them aligned and tight. Use galvanized nails or screws in the back to prevent corrosion.
It sounds like you are building a retaining wall. If you are going to backfill 3.5 feet the outward pressure from the soil behind the wall is going to be tremendous, possibly pushing all of the poles over since they are only 1.5 feet in the ground. Have you considered placing the poles in concrete to provide some strength, or maybe building a real retaining wall of masonry and then attaching the wood to the surface for visual effect?
You will also have soil particles washing out between the poles. Use a permeable barrier behind the wall to minimize this (you need water to drain, or it will just add more weight), or backfill with gravel/coarse sand to aid in drainage but prevent clay particle migration.
Sounds like a great design element. Good luck!
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