I have built this garden bed with ACQ timber. I am looking to get some suggestions from the community if I may. I have put the regular weed mat the bottom. I am looking to put some lining on the inside walls of the beds.I have seen people using thick plastic coverings but I am not too sure about it. Also do I need to do any caulking to fill out the gaps in between the sleeper? If yes which one is recommended.
All suggestions are welcome and highly appreciated.
Welcome to the Bunnings Workshop community @ravstk. It's great to have you join us and many thanks for your questions.
There is no particular reason why you need to put any plastic lining on the internal walls of the garden bed. The timber is H4 treated so it is suitable for contact with soil, the treatment is ACQ or Alkaline copper quaternary and won't affect growing herbs and other plants, and if your joints don't have large gaps only a minimal amount of soil particles will escape.
In saying that, there is no reason why you can't put a layer of thick plastic and I would suggest using builders film due to its robust nature. There's a couple of different thickness to choose from and those are 100um and 200um.
It would be worth considering whether using a filter or drain matting instead of the plastic would be a better option. If you have a look at @Adam_W's article on How to build a raised garden bed, in step six he talks about the use of drainage fabric and how to fix it up the sides of your garden bed. The fantastic @Noelle also has a great article on How to fill a raised garden bed which I trust you'll find useful in the next steps of your project.
I haven't personally ever heard of someone caulking in between sleepers before. I feel Adams method of using drainage matting would be a better option to stop soil particles escaping the joins if that was indeed the intended reasoning for applying it.
Please let me know if you need further information or have any questions.
Thanks Mitchell for the detailed response. I really do appreciate your reply. The main reason I wanted to line inside of the garden bed for keeping the soil chemical free ( even though I used micro pro sleepers). Just trying to be as chemical free as possible :). I 'll evaluate whether to use plastic barrier or non woven. Thanks again for your advice.
There is absolutely nothing wrong with trying to keep soil chemical-free. Personally, I have lined my own garden bed with the builder's film as I used pallet timber and some of the treatment of the timber was unknown. I also used it because the pallet timber is not H4 treated and therefore not suitable to be in contact with soil.
For peace of mind, I would advise using the builder's film.
Personally I wouldn't see a need to line the bed. The chemicals used in ACQ or microshades are definitely at the safer end of the scale. The quantities that may leach are likely to be very minor too.
If you want to stop soil from going out through the gaps I'd use a filter fabric or yes, you could caulk it. If you caulk it do so from the inside so it's not visible and look for a product that is classed as fully moisture resistant and drinking-water safe. It will need to be flexible too as sleepers tend to swell and contract with moisture & temperature.
You may find filter fabric or drainage mat is better in the base if you feel you need something there. With that soil depth, around 400mm by the looks of it, nothing will grow through from below anyway so realistically you may actually just be potentially impeding drainage.
Just looking at your structure there... will there be much material against the front face of that wall? If they will be above ground I'd just be a wee bit concerned about those sleepers pulling away from their posts. I explain why at 4:50 in this video.
Thanks for the advice. I have used a regular weed mat at the bottom of the garden bed, You reckon , I should change to drainage fabric? I do agree that I should have kept the post outside of it but I would beautify the outer side of the garden bed with some decking timber later on so, I decided to use the post on the inside. Thanks for all the advise , looking forward to fill it up and start planting some vegies
Hi @ravstk I do think you'd be better with drainage fabric in the bottom as it's designed more for that purpose. As I said though... not really seeing the need for it unless you are worried about wash-outs.
In a situation like that if I was suppressing weeds I'd just be laying cardboard or newspaper 8 or so sheets thick and that will block them out. They won't worry you again.
I in fact just posted about this recently on Instie in a garden bed I've built for a project.