Before You Line Your Grow Bed

I wont go into much detail on installing the liner. Basically all you do is cut it to size and lay it in the bed on top of some type of liner protection(underlayment). It is very easy.

What the upcoming instructional will focus on is leak prevention and also how to make water tight bulkheads. Here I will go into what you can use as a liner and provide some instructions on how to prepare your grow bed for the liner. But the main thing to keep in mind here is "You do not want to fix any leaks after the grow bed is filled with rock". Trust me, do everything you can to prevent them ahead of time.

So let's talk about what you can use as a liner. The best thing is EPDM rubber that you should use for your pond. Order a little extra when purchasing your pond liner. There is nothing better and it will last a lifetime if you maintain it properly. Unfortunately, it is a lot more expensive than other things you can use. I ordered extra with my pond, but still did not have enough for all of my grow beds. So I went as cheap as I could for two of the beds. Eventually I will replace it with EPDM, but for now the budget would not allow it.

So what to use? Basically anything that would line a pool, will line a grow bed. Of coarse, concrete isn't really an option, but you could use it. But for practical purposes you need something light and flexible for a, much smaller than a swimming pool, grow bed. Like I said, I did what my budget allowed, I went cheap. 4mil construction plastic is very cheap, so cheap you can double it up to provide more protection. It costs around $20 US dollars for a roll that will easily be large enough for a single grow bed. The draw back to this is, that it will probably need to be replaced in a couple of years. Which really isn't a problem since by that time I will need to clean the bed out anyway. So I can just replace it at that time, hopefully with EPDM. There are some precautions to take when using it however. Never leave it exposed to sunlight. It deteriorates rapidly when exposed to sun. 3 weeks and it's done, crumbling to a fine plastic powder. Do not scrape or drag it over ANYTHING. It cuts fairly easy, and you can't always see the cut. Tears look like wrinkles and can be overlooked if you are not careful. Use heavy underlayment, including roofing patch to seal the bottom of the bed.

UNDERLAYMENT

For EPDM, you can use anything. Old carpet, towels, rags, etc... For construction plastic(CP), you should use something that is one piece such as carpet or another layer of plastic(which is what I used on one of them). A single piece will not have seams and spots that can wrinkle the plastic(not as many anyway), which is a potential area for a pinch tear.

Here you see the underlayment I used for one of the grow beds.

I used the foam underlayment from the old pool.

GROW BED LINER PREPARATION

Vacuum out everything that is loose inside the bed. Make sure to remove or cover any sharp edges, ties and brackets. Cover all corners with padding. Tar, foam padding, and silicon work great for both applications.

For better leak protection I sealed the bottom of the grow bed with roofing repair patch(black tar like stuff) spread over the bottom half of the beds. Then I placed the underlayment on top of that. Keep in mind where you want your drain and overflow bulkheads to leave the tar off of that area until you have drilled the holes for them. The good thing about tar(roofing repair) is that it will seal the bottom to help stop leaks and protect the wood underneath from rot. I used it on two of the beds, the same two that I used the construction plastic for the liner. You can also use it to cover the brackets and straps to protect the liner from coming in contact with them.

Here you can see a strip of wood I used to keep the 2x4's together tightly, covered in roofing repair.

You can also see two of the three layers of 4mil CP.

I used two layers for the liner and a third as underlayment.

The top layer got tucked under and out of sight, but it is there.