Hello, sorry if I am posting duplicated subjects. Had a look but didn't find answers directly relevant to my project, so I hope you don't mind posting this here.
I would like to build a retaining wall using the Whites "Retain It" system. The wall would be about 8.5m in length. I plan on using Ironwood 200 x 75mm 2.4m Sienna treated pine sleepers. I am planning of a height three sleepers (about 600mm). I would also like to install a capping on top of the wall. It will be more of a garden wall than a retaining wall. I am planning to use whites 1500mmx75mm posts.
I'm aiming for a straight line version of:
My questions to begin with:
Thanks in advance for any advice.
Solved! See most helpful response
Welcome to the Bunnings Workshop community @steveof2620. It's wonderful that you've joined us, and many thanks for your questions.
For a retaining wall that needs engineering, there might be a stipulation on maximum post spacing. If the height of 600mm means you are not required to have the wall engineered in your state, then a span of 2400mm between posts is suitable.
If you need to cut sleepers to length, you can reseal their ends with TWA Woodcare 300g Ecoseal Tanalised Timber Treatment.
The top capping can be constructed from a sleeper, and Buildex 16-8 x 125mm Climacoat Type 17 Timber Construction Screws would be sufficient to hold them in place. You would screw directly through the capping and into the edge of the sleeper below. Try to offset your screws instead of running them all in a straight line, as per the image below. This will give the capping more rigidity. You might find that using a full-width sleeper makes the capping slightly disproportionate to the rest of the wall. You could either rip it down the length to make it slightly thinner or choose to use a 50mm thick version instead.
Whites recommends that you have around as much post in the ground as out of the ground, so in your case, the Whites Outdoor 1100 x 75mm Retain-iT Joiner Post should be adequate. You'll need a hole at least 300 x 300mm wide and the depth of your post. 40kg of concrete fills a 300 x 300 x 300mm cube. If you were to use the 1100mm joiner, that would require around four Bastion 20kg Rapid Set Concrete bags per post.
I look forward to following along with your project. Please let me know if you have more questions.
Awesome, thanks very much for your replay. That information is most useful. Thanks for taking the time to respond. Cheers.
Thanks again for the information you provided.
Couple of queries:
Does that sound OK or do you have other suggestions?
Also do I need some sort of drainage gravel to place under the bottom sleepers?
Australian Builders 20kg Quick Set Concrete is most certainly a suitable alternative. The post hole digger will make easy work of digging soil. If the ground is rocky, you might like to have a mattock on hand as well.
No drainage gravel is needed under the sleepers, but you might like to read through @Adam_W's step-by-step article on How to build a retaining wall. In step eight he shows how to lay an agricultural line behind the wall to remove excess water and divert it away from the wall.
Please let me know if you have more questions.
Sounds like you're on the right track now @steveof2620 one comment however...
If the wall is retaining any material at that height it may need engineering approval. Different councils have differing rules I believe but generally anything over 400mm likley needs some sort of design input as a minimum as you need to get deep and width of footing right to avoid failure.