Naturally Cool Cob Playhouse


This article was originally posted in Instructables and is reposted with permission from Adam Robertson.

cob playhouseHere in central California summers are very hot and dry. Being outside can be uncomfortable, so we wanted to create a naturally cool (cool as in temperature) area for our son. Since the ground here is full of clay, we thought a cob layer on a playhouse with a living roof would provide sufficient cooling ... and it works! This play area is one of the coolest spots on the property during the blistering hot summer heat. It also stays bone-dry inside during the winter.

Since I used scrap-wood and earth already available to me, I only had to purchase a few items. Total Cost: $30.00

Rather than focus on building the actual structure, this instructable covers the cobbing part of the project.

This project was spaced out over two months to give each step plenty of time to dry, settle, harden and adjust.

Step 1: The Structure

cob step 1Using some leftover wood from a previous construction project, I was able to put together a sturdy frame to hold the living roof (which is very heavy). I also used some oak limbs for columns in the front. Those limbs might look thin, but the oak-wood here is like iron, and will probably outlast the rest of the structure.

The living roof is around 5 inches deep, with a layer of roofing tar at bottom (dried properly), thin layer of gravel on top of that, a layer of old cotton rug found at the local thrift store on top of that, and finally the soil. I have 2-by-4s spaced out to help hold the soil in place (you can just make them out in the photo). Also, plenty of drainage along the edges for excess water to run out of. Note that there is plenty of roof hanging away from the house all the way around.

Step 2: Underneath the cob: stain, paint and moisture barrier

cob step 2To keep the wood dry, we caulked and painted the inside, and then stained the outside with a dark brown stain. Tar paper was used as a moisture barrier between the plywood and cob to prevent rotting.  You can see the black tar paper against the plywood. I then added some scraps of wood strips around 1/2 inch thick, and put a layer of wire fencing on top of that.
The result: sturdy wire fencing held 1/2 inch away from the surface. This will be what holds the cob in place.

You can also see that I have brought in rocks and earth around the base of the playhouse. This gives it more thermal mass, which is how this structure stays cool during the hot summer. Thermal mass will absorb the heat and release it at night.

I also added sand in front of the house for comfortable barefoot playing.

Step 3: Muddy Muddy Cob

Now comes the fun part: mixing and mudding. The dirt where we live is naturally clay, so the only thing we had to bring in was sand. Luckily, when our neighbors moved out the month before, they left a large sandbox full for us to use.

8/21/2013 7:36:57 AM

After reading all your great blogs and instruction, mine is just a small tip. I love hummingbirds but the yellow jackets like the sweet on the bottom of the feeders. So while cleaning the feeder; boiling water to wash them and making the nectar. I wanted to try to deter the insects from wanting hummingbird sweets. So first after rinsing the entire outer feeder w water then drying I took some salt and w a bit of water on my hands, rubbed the bottom of the feeder and between the roosts(where the hummers stand to drink). It worked! There is a yellow jacket nest just 10 feet away. Not one came to the feeder and the hummingbirds are happy and getting to know me. So thats it. Love Mother Earth Newsletters. Abbi

Subscribe Today - Pay Now & Save 64% Off the Cover Price

50 Years of Money-Saving Tips!

Mother Earth NewsAt MOTHER EARTH NEWS for 50 years and counting, we are dedicated to conserving our planet's natural resources while helping you conserve your financial resources. You'll find tips for slashing heating bills, growing fresh, natural produce at home, and more. That's why we want you to save money and trees by subscribing through our earth-friendly automatic renewal savings plan. By paying with a credit card, you save an additional $5 and get 6 issues of MOTHER EARTH NEWS for only $12.95 (USA only).

You may also use the Bill Me option and pay $17.95 for 6 issues.

Canadian Subscribers - Click Here
International Subscribers - Click Here
Canadian subscriptions: 1 year (includes postage & GST).

Facebook Pinterest Instagram YouTube Twitter flipboard

Free Product Information Classifieds Newsletters