Do you remember when we built a kid's tent a couple summers ago? Check out this post if you don't—it's a great rainy day project! We decided to take the concept of this tent and turn it into a cold frame, just in time for spring. We paired this cold frame with a mini version of our planter bed. You can adjust the size of the cold frame to the size of your planter bed and it will help protect your spring starters from too much rain, frost, snow, hail—or whatever the Seattle spring decides to throw our way.

Step 1

The first step is cutting:

With a miter saw set to 60° cut four 36" lengths of 1" x 2" with one side longer than the other making a trapezoid (the angle on these cuts aren't necessary, but are just for aesthetic purposes).

Crosscut (90°) a piece of 1" x 2" approximately 46".

Cut the 2" x 2" into a 46 1/2" length and a 45" length.

Step 2

Stack the 1" x 2"s in pairs on top of a piece of scrap lumber so that the points make an "M" shape. This way when the tent unfolds, the angles will line up and create a diamond where it overlaps. Mark the center of this diamond and drill with the 1" spade bit through both 1" x 2"s. This is going to be the top of the cold frame.

Dunn Lumber pro tip: Take full advantage of leftover scrap lumber! It can be hard to get a clean back on a spade bit hole, but with a piece of scrap lumber underneath it’s smooth with no breakage.

m shape for cold frame

drill cold frame with spade

drilling with a spade

hole for cold frame

hole for cold frame from spade

Step 3

Pause: Sometimes mistakes happen. One of our 1" x 2"s split—yes, even DIY blogs encounter DIY difficulties! With the large drill bit and the proximity of the hole to the edge of the wood, the likelihood of it breaking was pretty high. This can be avoided by using a smaller dowel and drill bit, or dropping the angled cuts and drilling farther away from the edge. Or you can risk it like we did, and repair any damage with a little wood glue and tape to set it in place.

gluing split wood for cold frame

taping wood for cold frame tent

Step 4

Next, we start the assembly. Slide your dowel into the hole of two of the 1" x 2"s.

slide dowel into hole

Step 5

With your 3/32” drill bit, make a hole through the outside 1" x 2" into the dowel. Secure in place with a 1 1/4" screw.

Repeat steps 4 and 5 on the opposite side of the dowel.

drill bit for cold frame tent

screw in cold frame

Step 6

Now, it's time to assemble the base of the cold frame.

Pre-drill the outer 1" x 2"s (the one attached to the dowel) to the 46 1/2" length of 2" x 2". Angle the 2" x 2" to match with the angle of the 1" x 2". Secure in place with 1 1/4" screws. Pre-drill and screw together the inner 1" x 2"s (not the one you attached to the dowel) and the 45" length of 2" x 2".

assemble base of cold frame

assembling base of cold frameconnecting base of cold frame

measuring cold frame tent

Step 8

It's time to cut out the plastic. Measure out a piece of clear polyethylene sheeting 4 ft. x 6 ft., plus the additional 3 ft. triangles that cover either ends. Refer to the diagram below.

We folded the plastic in half and measured it that way. Then we cut an inch-or-so outside of the lines so that there was sure to be some wiggle room.

diy cold frame tent design

measuring plastic for cold frame tent

marking plastic for tent

cutting plastic for cold frame tent

Step 9

Use a staple gun to attach the plastic covering to your tent. One side of the tent will be a flap you lift up. Attach the final 1" x 2" (46") to the base of the plastic piece with staples.

staple plastic for cold frame tent

stapling down plastic for cold frame tent

staple plastic down

Step 10

We don't know that much about tomatoes. So we went to the source of all knowledge—the internet—and found this helpful article from the Seattle Times. Valarie Easton interviewed local master gardener Wally Prestbo, who specializes in growing tomatoes in Seattle. According to Prestbo,"Tomatoes like weather that starts out warm, gets warmer and stays warm." There's still hope for growing tomatoes in Seattle! Here's what Prestbo suggests:

  • Choose the right type of tomato plant for your growing conditions: There are two kinds of tomatoes: determinate and indeterminate. According to Larry: " Indeterminate are bushy and compact, ideal for containers. They stop growing earlier in the season, ripening all their fruit over a two- to three-week period. Determinates do not need to be caged, staked, pruned or pinched (much). Indeterminate types (a.k.a. vining) are larger and lankier; they need more pruning and sturdy caging, which they make up for by producing fruit until killed by frost. These babies can grow 10 feet high. Whatever kind you choose, look for healthy green leaves and sturdy stems."
  • Location, Location, Location: Prestbo advises: "Plant where they’ll get at least six hours of sun and the most heat possible. The ideal is a raised bed basking in reflected heat off a south-facing wall." If you don't have a raised bed, we've got you covered with this great tutorial on how to build a planter bed!
  • Timing: Prestbo says: "Tomatoes can usually go into the ground by mid-May, when soil temperatures reach 50 degrees. I’ve found that late and early planted tomatoes usually end up pretty much the same." He gives his plants a heat boost by covering them with hoops draped in clear plastic during their early weeks in the ground. That's where this post comes in. Our cold-cover tent is the perfect solution to starting your tomatoes early in the season.
  • Fertilizing: Prestbo digs a balanced (5-10-10 or 10-10-10) organic fertilizer into the soil at planting time, then doses his plant with a liquid feed at the first of June and July.
  • Watering: Tomatoes need plenty; keep water off the leaves.
  • Pruning: Prestbo simply prunes up from the bottom of the plant so that no leaves are touching the soil, to protect from mold and blight.

cold frame tent

how to make a cold frame tent

diy cold frame tent

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