When you’re looking to put in a wood pond retaining wall, there’s a few things you’ll want to know before you start.
Firstly, you’re going to want to know how long it takes for the wood to rot, so you know when you’ll have to replace it.
After that, you’re going to want to know how much wood you need to use, so you’ll have an idea of how much it’s going to cost you.
Let’s get into the specifics.
Wood Pond Retaining Wall: How Long Does it Last?
The wood you use for your wood pond retaining wall is going to be in constant contact with soil and water.
That means there’s going to be a lot of bugs and fungi that want to eat it.
Sure, you can use pressure treated wood, but that stuff is only rated for about 40 years. You might be able to get away with using it for the frame of a pond, but you’re definitely going to need something to protect it from the water.
If you’re going to use a wood pond retaining wall, you’re going to want something that lasts longer than that, or you’re going to be replacing it every few decades.
To do that, you’re going to have to protect the wood. Now, you might be thinking that you could use liner to prevent the wood from coming into contact with the water, but that’s not going to work. The wood will rot from the inside, and then you’ll have a mess on your hands when it all starts to fall apart.
You could use a wood preservative, but they’re not going to last long enough for your purposes. They’re meant for things like garden sheds and fences, where they’re only partially in the ground.
What you need is something that’s going to last a lifetime, that’s specifically designed for wood that comes into contact with soil and water.
There’s only one option that fits the bill: EPDM rubber. It’s the same stuff as pond liner, but it’s a special type that’s designed to be buried, so you can use it for all of your wood pond retaining wall.
EPDM rubber is so safe, in fact, that it’s even approved for use with drinking water. It’s completely safe for your fish, too.
It’s also very easy to use. All you need to do is cut it up and staple it to your wood pond retaining wall, and you’re done. If you’re using more than one sheet, you’ll want to overlap them by 6 inches, and then you’ll be able to use some bonding adhesive to stick them together.
Wood Pond Retaining Wall: How Much Wood Do I Need?
This totally depends on how big your pond is.
If you’re going to have a small pond, then you’re going to need less wood. If you’re going to have a big pond, then you’re going to need more.
Don’t worry, I’m not leaving you hanging here. I’m going to do the math for you.
To measure the amount of wood you’ll need, you’ll need to find out the perimeter of your pond, and then divide that by the length of each length of wood you’re going to use.
When you’re measuring the perimeter of your pond, don’t just go by the perimeter of the top of pond. You’ll want to measure the perimeter of the bottom of your pond, too. You’d be surprised at how much difference it makes.
The formula you’ll want to use is:
amount of wood you need = (perimeter of top of pond + perimeter of bottom of pond) / length of each length of wood you're going to use
If you’re using 2x6s as your lengths of wood, then you’re going to want to divide by 6.
Of course, you do have to take into account that some of your lengths of wood will be longer than others. That’s why you’ll want to divide by the average length of wood you’re going to use.
If you’re not sure what length of wood you’re going to use, I can tell you that for small ponds, 8 feet long 2x6s are usually long enough, and for large ponds, 12 feet long 2x6s usually do the trick.
As you can see, by using longer lengths of wood, you can reduce the amount of wood you need drastically. That’s because the longer your lengths of wood are, the less wood you’ll be using per square foot of your pond.
With small ponds, you can usually get away with using 2x6s, but if you’re using 12 feet long 2x6s, they might start to sag a little, so you might want to use 2x8s instead.
As for the heights of your wood pond retaining wall, you’ll probably want to have them at least 6 inches high. This will give you plenty of depth, and make it so that you don’t have to do any digging. You’ll also be able to put in a pond lining that’s 12 inches above the water level, so that you can have a nice, natural looking edge to your pond.
Anything under 6 inches is going to be a little bit too shallow, and will make your pond look like a little puddle of water. 6 inches is the absolute minimum, but I’d recommend going higher if you can, because it’ll give you more planting space.
If you’re looking to have a really big pond, then you’ll want to have a look at the design considerations section of our guide to building a pond with a liner, because you’ll want to do a little bit of digging as well.
