There are many ways to put materials together to design and build a raised bed. Here are some guidelines for putting together a very solid, long-lasting elevated garden area using Trex®. Using recycled products for building along with growing your own food, herbs and cut flowers can all help you develop a productive, beautiful and sustainable landscape.
- Measure out the space where you want to build your bed(s). Having multiple raised gardens will allow you to rotate crops or to diversify whatever you choose to grow.
- If you want to irrigate your bed(s) set up PVC irrigation pipe to bring water to the inside surface of your container at the finished soil height when it will be filled.
Set in your posts. In this case we are using hollow vinyl posts used for fencing. The squared shape will make connecting boards easy and the vinyl can be easily cut, drilled and filled to give it weight. To keep your posts stable, dig deep holes, at least 12” deep, and set them with concrete footings.
- Cut your Trex® boards to size with a saw. It cuts as easily as regular wood.
Predrill holes for lag bolts through the posts so you can easily mount the boards. You may prefer to temporarily mount the boards with single screws (one board layer at a time) and then drill your holes and bolt them in place.
- Build your height one set of Trex® boards at a time. (Other materials like vinyl and wood can be used for this same design.)
If you have a problem with burrowing pests like gophers or moles, line the bottom of your garden bed with screening like ½” metal lath (or hardware cloth). This should keep critters from entering from below.
Once you reach the height you want, cut the fencing posts off so they are no higher than the sides of your garden bed.
- Fill the hollow posts with concrete to make them strong.
- Top the filled vinyl fencing posts with post caps. You can uses simple covers or get creative. You can use solar lit caps or wire up low voltage lighted caps. There are a number of designs to choose from and you might even want to adapt a fence cap to hold poles for attaching netting or roofing over your raised garden bed.
- Fill you raised bed with a mixture of rich soil that will best support whatever you plan to grow.
Set up a drip system or other type of irrigation system to efficiently water your bed. If you have multiple beds you may want to include individual water shut-off options for more control.
Note that if you are using Trex® boards horizontally, lengths over four feet — if the board is not thick enough — can bow slightly unless you bolt them to stabilizing uprights. Other than that, the material should endure for decades. It comes in an assortment of natural tones some of which may fade slightly over the first few weeks but then should maintain color intensity for many years to come.