Building a wood shed using slipform stone masonry

Back in November, Laire and I discovered that we would eventually move into Thor’s Den, a beautiful, uninhabited dwelling residing at the Keep that needed a little love and a little work to finish its construction.

Laire, my in-house architect, decided we needed to add a separate bedroom, as the home only came with a sleeping space in the loft. He also thought that the wood shed, which was on the south end of the house, should instead be on the opposite end, adjacent the driveway, so that you could drive a truckful of firewood right up to it. So we would convert the existing wood shed to a bedroom, and add a new wood shed to the north end. We consulted with Deryk, and he was game. Which was great, because we had no friggin’ clue how we’d do any of it without him.

Converting the old wood shed to a bedroom wasn’t all that hard. Before we got there, the shed had been used to house a couple goats for a while. Our billygoat liked to sharpen his horns on the concrete wall, and the walls and floor were probably well infused with his scent. So we did a little cleaning first. We like to get things “broom-clean” around here. Then we added an insulated floor and insulation on the walls and ceiling, and we shut the room in with windows and a door. Trim went on, then cedar shingles, and we’re now working on the drywall. Now, all of this took a helluva lot longer to do than it did for me to type those few sentences. But from the outside, you can see we’ve made some progress!

Thor's Den with goat in wood shedWood shed turning into bedroom

Laire shingling bedroom Bedroom close to done

Thor’s Den is a very solid structure whose walls are mostly stone and reinforced concrete, built using a technique called slipform stone masonry. More than just charming in appearance, these walls have enough strength to support the weight of the hill that is bermed against the back of the home, which greatly helps to moderate indoor temperatures year-round.

But to add a new wood shed, we’d have to extend this concrete wall, since this extension would still need to support that hillside in behind it. So we got a pal to dig the dirt all out for us, right down to ledge. That was step 1. Easy peasy.

Next, we had to pour the footing. That required building some pretty clever forms, because around here, ledge is rarely just flat. It’s all kinds of crazy ancient mountain shapes. So piece by piece, we had to build some pretty intricate forms out of various pieces of wood to contain the concrete that would become the footing. I let Deryk figure out the math mostly. He just got me to hold things, hammer things, or cut things, which I did gladly. In the end, we had concrete that became one with the ledge. I don’t think a strong wind is going to blow this wall down easily.

Footing forms along uneven ledge

Pouring the footing Concrete becoming one with ledge!

Then we attached slipforms to the footing forms to start filling up with rock and more concrete. Slipforms are just frames made from 2x4s with plywood on one side. You can make them whatever sizes you need and reuse them. It’s important to brace them to make sure they stay square and level, and also that they don’t burst open from the weight of the concrete and rock they’re meant to contain.

When you’ve done a couple levels of forms, you can remove the forms on the lower level and reuse them for the next level up. Sometimes they’re a little tricky to take off, especially when you have PVC drainpipes passing tightly through them. But as you can see below, Laire was all smiles.

Our buddy Wayne got involved with this project, mixing all the concrete for us whenever we needed it and helping us assemble and disassemble forms. He’s been a huge help.

Pouring the foundation using slipforms

Wayne and Deryk preparing the last level of forms Removing the first forms

And there’s the finished wall!

The finished wall after removing forms

Now I’ve neglected to mention all kinds of critical details of how this wall got built, like how the slipforms were properly braced and wired together, how we criss-crossed the entire structure with reinforcing rebar at particular intervals, how we fit the stones around the rebar and made sure there was still enough concrete in between opposing stones so that our wall didn’t fall apart, how we had to get the concrete a particular thickness or runniness depending on what stage we were at, how we even got some of those giant rocks lifted into place in the first place, and how I repeatedly held up the entire process because I’m too finicky and I can’t help getting lost in the details.

Oh, and obviously, that we’re not actually done building the wood shed. We’ve only just done the wall. The floor is next. And then the timber frame. Then the roof. There’s lots of steps in building things. Lots.

But I don’t have time to share any more details right now because it’s harvest day tomorrow, and we also have giant rubbermaids of blueberries to preserve. Man, I’m such a slacker!