This is Part 19 of the 20 part series on building a brick oven. To see more, visit The Ultimate Backyard Brick Oven Tutorial: How to Build Your Own.
We have reached the last major milestone of this backyard brick oven project: The all important roof. Throughout this whole project, I have dreaded…the roof. Why? The roof is what keeps out all of the rain and snow from the oven. If you know water, you know that it finds it’s way through a lot of things. Tiny cracks, holes, or seams are no match for water.
Why Water is a Problem
You may be wondering, what is wrong with water getting inside? It’s just all masonry. Bricks can get wet, right? Yes, that is true. But, there are three issues that I don’t want to deal with.
First, when water water gets inside, the bricks absorb the water. Since water boils at <300 degrees, it would be very difficult for the oven to reach cooking temperature of >500 degrees until all of the moisture is gone. Therefore, before you are able to cook, you have to let the fire drive off the moisture. Of course, this adds time to the cooking process.
The second problem with all of the water soaked masonry is the difficulty in making a fire. Since I have already made some fires in the oven, and I didn’t have a roof, I have started a fire after it had rained on the dome. Let me tell you, it makes the beginning phases of fire building much more difficult. Why? It is kind of like making a fire in a steam room. All of the water inside vaporizes, but it doesn’t have a good way to get out quickly. Therefore, all of this steam smothers your fire in the beginning until it gets burning nice and hot.
Third reason that water is no good for a brick oven is the freeze/thaw cycles. While I haven’t experienced this yet, I think it would be bad on the oven for water to get inside of the bricks/mortar and then freeze. Have you ever seen a pothole on the road after a freeze/thaw? Well, I don’t want a pothole in my oven.
The Roof Materials and Design
After thinking about quite a few options, I decided to go with a flat roof constructed from concrete board and covered with rubber EPDM roof. The rubber will last a long time and keep water out, while the concrete board will provide a fireproof roof for the rubber roof to lay on. Also, along the edges, I install drip edge. This keeps the water away from the brick walls as much as possible.
- (1) Rubber EPDM piece big enough to cover the roof
- (2) Concrete boards
- (3) 8ft drip edges
- Silicone and Roofing Cement
- Gasoline (just for cleaning the rubber roof)
- Aluminum flashing (Roll, step, and corner)
Here, you can see the start of the roof. I used aluminum metal studs as braces to support the concrete board roof.
One important design point to consider was the slope. In reality, a flat roof isn’t actually flat. If it were flat, water would tend to pool on top. Therefore, a flat roof needs to actually be sloped. The back of the roof needs to be an inch or two lower than the front. It still looks flat, but it is ever so slightly sloped to let water drain off of the back.
It took two pieces of concrete board for the roof. In hindsight, it would have been a good idea to raise the seem in the middle up. It started to sag and water now runs to the middle. Also, notice the back has a layer of bricks missing. This is so that water can drain off of the back.
As I mentioned earlier, water finds its way into every little nook and cranny. To seal of these gaps, I used roofing cement and silicone. The cement was used around the masonry, while the silicone was used between the flashing/drip edges and rubber roof.
Roof Construction Begins
Now that we know which materials we are going to use (concrete board, rubber roof, roofing cement, and silicone), we get to start building.
The first step is to lay out the rubber roof and cut it to size. I found it easy to lay the roof directly on top of the oven and trace the brick with a box cutter. One tricky section is the chimney. As you can see from the picture below, I decided to cut a seam along each corner so the rubber would fit over the chimney. If I did it again (which I won’t for a long time I hope!), I would try to not cut this seam. Instead, I would try to cut a square a little bit smaller than the chimney and see if the roof would “squeeze” over top of the chimney. That would give a tighter fit and get rid of a couple of extra seams where water intrusion can occur.
After cutting out the roof, I decided to put down some aluminum flashing on the back drip edge section. I thought that any additional protection from water couldn’t hurt.
The back of the roof has aluminum flashing as an extra step to keep the water out.
The finished roof before putting down the drip edges and sealing it up.
After getting the roof laid out and cut to size, the next step is to seal out the water. As mentioned earlier, we will be using roofing cement and silicone to seal out the water. And since silicone wouldn’t seal very well when applied to a dirty roof, we’ll need to clean the roof. No, you don’t need any special cleaning materials. Gasoline will do the trick.
After cleaning the edges with a rag and gasoline, the silicone has been applied around all edges.
After applying silicone around the edges, it is time to install the drip edges. On the side of the drip edge that will contact the brick wall, roofing cement should be applied. This helps secure the drip edge and again helps keep out water.
Applying roofing cement to the wall side of the drip edge before installing the drip edge onto the roof.
The last step in the roofing process is installing the step flashing and corner flashing around the base of the chimney. While I didn’t get any pictures of this step, I didn’t do anything fancy. I put the step flashing and corner flashing against the chimney and proceeded to silicone the heck out of the base (between the flashing and rubber) and go crazy with the roofing cement between the chimney wall and flashing. Do you understand why I didn’t take a picture here? Yes, I think there has to be a better way to flash a chimney.
Well this is the final step of the brick oven construction process. It has been a long journey, but a great one where I learned a lot. In the next post, I will show the final product.