I divide the process of adding a DIY greenhouse top to a raised garden bed into two steps. First, build a framework. You can choose from cold frame plans or hoop tunnel plans. Next, make a cover for that frame, to enable the greenhouse effect. The design of the frame will depend on the choice of the cover.
I’ve collected these 13 plans that are very simple and easy to build, and some can be completed on a very low budget using cheap or recycled materials. Also, keep in mind that you can incorporate a greenhouse topper in your DIY raised bed plan or you can add a greenhouse cover as an attachment later.
Also included are useful tips on how to mount and anchor PVC hoops and how to attach plastic sheeting. In addition to plans, I’ve added some creative design ideas for raised garden beds with greenhouse tops.
Here’s the list of all of the material options for frame and cover that are described in this DIY guide.
You can build a cold frame from these four materials:
You can build a hoop tunnel greenhouse topper from these six materials:
- Flexible PVC tubing (white)
- Electrical PVC conduit (gray)
- Electrical Metallic Tubing (EMT) conduit
- Masonry Ladder (this one is the simplest)
- Willow or Cedar branches
- Corrugated Polycarbonate (this one is awesome)
Then, there are four greenhouse cover materials to consider:
Now, let’s get to examples and plans for all options listed above.
1. Removable High Hoop Tunnel Greenhouse Topper Plan
One of the best plans for a greenhouse top is found on ApartmentTherapy. It’s a high hoop tunnel framed from white flexible PVC tubing. It is then reinforced with metal wire mesh and covered with plastic sheeting. But the best part of this design is that the top is completely removable. It’s hinged on one short side and its opening angle is constrained by two metal chains. The only con is that when fully open it can be blown away by the wind.
2. Metal Conduit Polytunnel Plan
If you get a lot of snow in your area and prefer a more rigid construction then this greenhouse top plan by Mr. Chiots at ChiotsRun.com could be perfect for you. They used a very inexpensive EMT conduit (Electrical Metallic Tubing) to build a hoophouse at a fraction of the cost. Bending a metal tube into a perfect arch is not an easy task. This plan explains exactly how you can make a polytunnel with or without hoop benders. Once they are bent, attaching metal hoops to your raised bed is as easy as with plastic tubes.
3. PVC Electrical Conduit Hoop Tunnel Plan
You’ll recognize the PVC electrical conduit tubing by its standard grey color. This raised garden bed greenhouse plan is very long and quite wide. According to doityourself.com, it needs 10 feet of grey conduit and some conduit PVC clamps, to build a greenhouse top of this length. To attach the plastic painter tarp, velcro strips and tarp clips are used. Pretty clever and convenient. The design allows you to easily remove the cover when you need to access the garden bed. When desired, you can remove the entire cover or end pieces only. See the step-by-step building guide.
4. DIY Greenhouse Top Made as Retractable PVC Hoops
At some point, you will want to expose your covered raised garden bed to sunlight. One way of doing it is to build a retractable greenhouse top. Vern Harris at grit.com came up with PVC hoops that glide on aluminum rails. You pull two ropes and the entire bed gets exposed. You don’t need to be a DIY guru to follow this clever hoop house plan. See the details.
5. Greenhouse Cover Framework Made from Masonry Ladder
Here’s a quick and easy plan for building a greenhouse top from Masonry Ladder. It’s basically a metal wire mesh, similar to the kind you use for front yard signs, only longer. This mesh is also called Ladder Mesh or Ladder Mesh Reinforcement, as it’s used to reinforce concrete structures. You can get it at your local home improvement store. The wire diameter is quite small so it bends easily. You don’t even need to attach the mesh to your garden bed. Simply stick it into the soil deep enough. Follow this nice DIY video and step-by-step instructions to build one yourself.
6. Raised Bed Greenhouse Top Made from Cedar Branches
This is the quickest and the cheapest greenhouse top plan suitable for those who did not expect sudden frosts. It can be made in 45 minutes, according to the author. To create arches, cedar branches were used. Willow branches or any other wood species with flexible branches would work as well. The branches are stuck into the ground and a wood plank is tied on top of them with a nylon thread, to maintain a sturdy frame. Arches are then covered with clear plastic and … done.
7. DIY Corrugated Polycarbonate Garden Bed Plans
In this video, Gary from The Rusted Garden explains how he builds a mini raised bed greenhouse for under $25 using corrugated polycarbonate. It’s an extremely lightweight material that is going to last for over 10 years. The small bed (1 ft. x 6 ft.) is covered by 1 standard-size sheet. This simple DIY plan is somewhere between a cold frame design and a polytunnel. Bend the plastic sheet into an arch and insert it inside the bed frame. Hold it down with two bungee strings. The bed itself is made from one 2×4 board. What a neat idea! We love it.
Also, see this amazing DIY polycarbonate plan on landscapejuicenetwork.com. This is an easy to build hoop tunnel greenhouse top. Build a rectangular topper frame using 2×4’s. Size it to match your raised bed shape and dimensions. Attach three PVC arched tubs using metal clamps. Cover them with corrugated polycarbonate and hold it in place with nylon rope. Screw three hinges to the topper frame and attach it to your bed. And you’re almost done. All you have left is to figure out how to close the ends. Plastic sheeting would work.
8. DIY Raised Bed with Hinged Cold Frame on a $25 Budget
Nick at gardenlogblog.com wanted to extend the garden season on his raised beds. So he used leftover wood to build 4 cold frames. He added 2 square toppers to fit over the top of each raised bed, using hinges. He then covered them with UV resistant plastic that is used for greenhouses. The overall project only cost $25, mainly to pay for plastic. This allowed him to plant earlier.
The DIY greenhouse tops worked great. The only change Nick suggests applying to his design is to angle the tops so the water doesn’t get collected on the plastic. See more details.
9. Mini Seed Greenhouse Cold Frame Plan Built with Recycled Glass Windows
If you want to start planting earlier in the season, you need to start growing your seeds earlier. And this idea for a small seed greenhouse from instructables.com could be just what you need. It doesn’t come with a detailed plan but it’s very easy to figure out. Here’s how you build it. Find an old window with glass. Cut wood planks to be two inches shorter than the length of the window. They will form the long sides of the raised bed. Screw in or nail down three cross planks, to keep the long planks together. Cut planks for shorter sides and use them to form the bed’s rectangular frame. Make sure that the shorter sides are tapered down, so then the top cover will be slanted. Use two hinges to attach the window to the box.
Small raised bed cold frames are great to foster seedlings early in the spring. But they are also good for growing tall veggies through fall, and in some places even into winter. But you will need to build a deeper frame. It should look something like the cold frame in the image above. To increase durability, re-caulk the old windows if needed and paint the box. You should also incorporate some means to let the air out. In this plan, the designer included a common air went register.
10. Galvanized Steel Raised Bed Plan with Polycarbonate Cold Frame Cover
If you prefer a raised garden bed plan that will last longer than any other type then using Corrugated Galvanized Steel to make it is the best idea. Cassie, the Certified Master Gardener and founder of Growfully.com, offers a complete step-by-step guide on how to build Galvanized Steel Raised Garden Beds. You will also learn how easy it is to turn them into cold frames. You simply lay a plastic greenhouse panel on top and hold it down with something heavy.
You can apply the same cold frame idea to raised bed designs made out of wood. The twin-wall greenhouse Polycarbonate panels will withstand some light snowfall and you can even add some supports under them.
11. Large DIY Plan Built from Rigid 3/4″ PVC Pipe
The above PVC pipe plan requires some pretty elaborate work to complete. But it’s all worth it as it’s quite roomy and can handle tall-growing vegetables. It’s installed on top of a waist-high raised bed and can be lifted up on one side. It’s built from 3/4 PVC pipe and uses lots of connectors. Watch the video to learn how it was built. Below the video, you’ll find the material specs and dimensions.
12. Large Raised Garden Bed with Greenhouse Top Made from Wood (1×2’s)
Here’s a great DIY plan presented at instructables.com. It includes drawings, dimensions, a materials list, and even a cost estimate for the raised bed and the greenhouse top shown above. The top is made from 1×2 lumber. The raised bed is 16 feet long and 3 feet wide and is somewhat elevated.
The designer of this plan wanted to build a raised bed greenhouse that will protect the planted vegetables from chickens, cats, squirrels, and caterpillars. He also included a gable roof, for taller veggies to have enough room to grow. On his page, you’ll also find some tips on using logs to retain moisture inside the raised bed.
13. Simple Cold Frame Plan with a Removable Polycarbonate Cover
Watch this awesome video to learn how to build a 4 season cold frame with a removable Polycarbonate cover. It’s an easy project, and you can use this plan to create a quick and simple cover for your raised bed. All you will need is a standard size 2′ x 8′ Polycarbonate roof panel and screws that are used on plastic, to make a strong and durable greenhouse top.
Ideas on How to Attach Plastic to Greenhouse
Use Tarp Clips
At doityourself.com, they suggest using tarp clips to attach plastic sheets to a wooden raised bed. They prefer the EasyClip brand and you can buy them here. First, attach the clips to plastic every 2 to 3 feet. Then, pull the clips snug and screw them into the wood. You’ll be able to easily remove the plastic when needed.
Make DIY PVC Clamps
To secure plastic to a PVC greenhouse or to a raised garden bed, use the ingenious idea shown above. Mount PVC pipes along the sides of your wooden box – these will be your rails. Now make clamps. Cut the leftover pipe into small 2″ pieces and remove about half-inch material from each piece. Wrap plastic around the rails and clip it with your just-made DIY clamps. Install a few clamps within the length of the bed. Watch how it’s done in practice.
Make DIY Clamps from Garden Hose
Shelley at sowanddipity.com has this idea on how to attach plastic to PVC hoop house (see the image above). Cut the old hose into 5-6 inch pieces and then slice each down the middle. Now you’re ready to use your DIY clamps as shown. And check out her $50 DIY PolyTunnel greenhouse tutorial.
Use PVC Tape
To attach plastic to garden hoops or to reinforce the tie-off spots, use this idea from grit.com – shown above. Buy the 10 or 20 mil PVC tape, also called Pipe Wrap Duct Tape. It’s designed for outdoor use. Place a piece of tape over plastic and punch 4 holes in the tape and plastic. Then run a rope through the holes and tighten it.
Ideas on How to Mount, Anchor and Connect PVC Hoops
Here’s the DIY idea from Sarah at Secret World of a Housewife on connecting parts of a greenhouse top. She just used short-length hose pipes to connect canes, as shown above. But the same approach can be used for connecting PVC hoops, as long as diameters fit. It’s so simple!
If you’re asking yourself how to mount PVC pipe to a raised garden bed to create a greenhouse top then consider this classic approach. Here, we have a low hoop tunnel made up of a few arched pipes and plastic roll-ups. Notice how the pipes are attached from the outside using common galvanized pipe straps, two per pipe per side. They are very cheap – you can get some here for only 34 cents apiece. For a bed design such as the one shown above, you’ll need 20 straps, totaling just under $7 plus shipping.
Alternatively, you can attach galvanized pipe straps to the inside of the raised bed. My hunch is that attaching them from the inside is more practical, as it’ll be a more robust construction. To make your greenhouse topper design even more practical, attach larger diameter PVC pipe sleeves first, then slide the smaller pipe inside. This topper is easier to remove or modify when desired. Image source: homesteadandchill.com.
If you’re short on metal clamps, you can use the Galvanized Pipe Hanger Strap. Cut it into short pieces and mount them just as you would mount straps. They are easy to bend. They are sold in rolls here.
The money-saving trick here is to use one strap only but also drive a screw through the PVC pipe into your raised bed frame, as shown above.
One of the popular approaches to anchoring a PVC hoop is to use rebars. You hammer a piece of rebar halfway into the ground and then slip the pipe over it. Make sure to push the pipe all the way to the ground. If the soil is loose then you would want at least 2 feet long pieces of rebar. Visit motherearthnews.com to see how this method is used in practice. You can get a 10 feet long rebar at Lowe’s for just under $6. Cut it into five 2-ft pieces, and each will cost you just over $1. Pretty cheap!
To keep the PVC hoop permanently in place or to make sure it won’t slip out of the rebar, tie it to the raised bed with galvanized pipe strap and a couple of screws. This will help with keeping the greenhouse top secured during strong winds. Find more details on this idea at grit.com.
You may have some spare green fence stakes or fence posts laying around in your yard. You could use them to mount your PVC greenhouse hoops in the manner shown in the image above. Drive a post into the ground and then snap the pipe over it or simply bolt the pipe to a post (as shown above). I would also tighten a zip tie at the lower end, to be sure the hoop is totally secure on the stake.
For the most robust hoop mount, consider this very different idea for anchoring. Developed by an Organic Gardener and Permaculture designer, it works better for larger diameter PVC pipes. Hammer a steel pipe into the ground, slip PVC hoop over it and then drill through the plastic pipe and steel pipe and bolt both securely to your garden box.
Greenhouse Top for Raised Bed Design Ideas
If you are required to retain more heat to grow your plants then a raised garden bed with a greenhouse top is the perfect solution! You can choose to go with a cold frame or a hoop tunnel plan for your top, or with a plan that is something in between. Let us showcase different designs for a greenhouse over a bed.
The above design is an easy to build tall trapezoid. It’s made with 1×2’s. Rolling up plastic sides is one popular solution. The short sides are permanently closed with Polycarbonate panels. Overall, this is a pretty compact design that allows you to grow tall plants and climbing vines.
When you just planted your seeds, you can create a greenhouse effect by covering your raised bed with old glass windows. As the plants grow bigger, raise the windows higher. This is a very simple but efficient topper design.
Or build a permanent triangular cold frame over the bed. This frame can serve two purposes. One is to install greenhouse plastic over it when plants need more heat to grow. Another is to cover the bed with a protective metal or plastic mesh to prevent birds and animals from snapping berries during the picking season. It’s built using 1″ x 2″ lumber and carpenter’s galvanized metal connectors.
Here is a more sophisticated idea for a greenhouse top. It’s composed of folding windows that can be opened or closed depending on the season or the amount of sunlight the plants need. This design also allows for letting the fresh air in while still retaining more heat inside the bed. And the windows can be made from Polycarbonate – it doesn’t have to be glass.
Here’s one creative idea. A portable raised bed on wheels and with a greenhouse top that can be opened and closed. You can drag it near the sun or away from direct sunlight any time you like and cover it up when you feel your plants need shelter.
To build a garden box on a budget, using recycled wood is a great choice, especially for DIY projects.
You can reuse old window frames to make a cover. They’ll keep your plants shielded from harsh weather conditions and create a greenhouse effect inside.