This outdoor stove/oven/grill/smoker is made of concrete blocks and firebricks so that it will last a long time.
PHOTO: MEEMEE KANYARATH
This DIY, wood-fired, outdoor masonry stove can be used four ways: for baking, grilling, cooking, and smoking. Whatever your cooking needs, our outdoor stove/oven/grill/smoker can do it, thanks to interchangeable grill grates and griddle surfaces. If you want to grill steaks or fish, use the grill grate. If you want to bake bread, slide on the steel griddle, stack some bricks on top to retain heat and add the door to hold in the heat. If you want to use the stove top, just slide the metal plate (or griddle) over the top of the firebox.
The MOTHER EARTH NEWS editors and I wanted to design a highly efficient, multi-purpose stove that uses little firewood (or charcoal) and retains heat for baking and cooking. So, we included a thick insulation layer of lightweight perlite/cement between the firebox and surrounding concrete block, and we included a removable door. This design holds the heat in the firebox where it’s needed. (Perlite is the porous white stuff often found in potting soils. You can buy this mined mineral product at garden centers.)
You can build the outdoor oven in stages, a few hours at a time. (You’ll need a few days between some steps.) Check local building codes before you start building. The oven is made from materials you can buy at local hardware or building stores. You may be able to find some of the materials at a salvage yard, too. (See the materials list and the building diagram). Detailed instructions for building the outdoor brick oven are below. Even if you only use it to bake bread, you can save enough money in one year to more than pay for the $300 cost.
Ideally, the stove is built to a comfortable height with concrete countertop space on each side, plus a roof to protect against the elements. We covered the concrete blocks with tile, primarily for aesthetic reasons, but you could apply stucco over the blocks, or just paint them. Having an outdoor sink and storage space nearby is also convenient.
Our outdoor oven requires a fire in the firebox for about 45 minutes to one hour to reach a baking temperature of 450 to 500 degrees Fahrenheit. Or, if you want to grill, you can start in less than half an hour. For comparison, it can take about three hours to get a clay earthen oven up to proper baking temperature. That’s a lot of time and firewood expended, which really adds up if you’re using the oven frequently. The firebrick used in our stove reaches cooking temperature more quickly than clay because its higher density makes it more efficient at conducting heat.
Another key design element is the firebox size — not too small, not too large, but just right. Properly sized fireboxes heat up quickly, have improved combustion, produce less smoke and stay hotter longer. We measured cookie sheets, bread pans, medium and large roasting pans, canners and baking dishes to arrive at our optimal firebox size of 13 inches wide by 28 inches deep by 13 1/2 inches high.
Bread! Pizza! Barbecue!
If you like to cook, you’ll love this stove. Our favorite cooking technique involves cooking foods in rapid succession at dinnertime. We like to start out with pizza when the oven is about 500 degrees. The pizza bakes in about three minutes. After that, the oven has cooled to 350 to 400 degrees — perfect for baking bread. (The temperature of the air in the oven drops momentarily when you open the door, but the brick is still hot and maintains temperature.) Sometimes we throw in some potatoes at this stage if we want baked potatoes. When the bread is done after about an hour, we bake various combinations of veggies (and sometimes dessert). You can bake a lot of food from one firing. And if you want added heat — to bake extra loaves of bread, for example — just keep a small pile of coals burning in the back of the stove.
Another efficient method is to grill meat and veggies before the baking phase.
Our plan includes a grill grate at midoven height for grilling food closer to the coals. This grill grate adds extra space for baking, almost doubling the capacity of the oven. It also provides space for a tray of water for bread recipes that require steam.
The outdoor oven is a super barbecue! About 95 percent of the smoke goes up the chimney after the fire is going strong, making for a pleasant grilling experience. There are two grilling surfaces (one on top and one at midheight). The heat remains steady with minimal fuss. And if you like more control over the grilling temperature, adjust the damper and add the door.
The outdoor oven provides the main requirements for a good smoker: It retains heat well, plus the damper and the vent in the insulated door allow you to control airflow. Use the grill grate (shelf at midheight) for holding food. Keep a small fire going and cook until tender. Unlike many smokers, large chunks of meat (even wild game) can fit easily in this stove.
Canning in Summer
Using the stove for canning keeps extra heat out of your house during some of the hottest times of year when lots of vegetables are ripening. Just close the oven door and put the steel plate on the oven to use the cooktop. You can also use the stove top for sautéing, stir-frying or anything else you’d use a conventional stove top for.
Setting a canner on the grill instead of the stove top is even more efficient because the fire heats the canner directly instead of transferring heat through the steel plate.
In addition to all the other cooking options, you can cook in a Dutch oven placed inside the firebox. Dutch-oven cooking is ideal for stews, chili, roasts, certain types of breads and rolls, beans and some desserts. It’s more efficient to use the Dutch oven inside the outdoor oven than outside on a campfire because it requires fewer coals.
Why Not Clay Instead of Brick?
We chose our materials after extensive discussion with several outdoor oven experts, including John Gulland, Kiko Denzer, Carol Mack and John Stuart. I love using earthen materials — such as earthen plaster, adobe and earthen floors — but an outdoor oven is somewhat vulnerable to the elements. We wanted a durable stove. Our masonry stove should last many years longer than an earth oven. An outdoor earth oven can easily be damaged or destroyed by driving rain, snow, freezing weather or even termites.
The stove requires almost no maintenance. There’s no need to clean grease out of the oven because it will simply burn away next time you use it.
The outdoor oven won instant approval from my mother-in-law. She recognized its practicality and was all smiles. Cost to build outdoor oven: $300. Approval from mother-in-law: priceless.
The wood-fired stove is not only versatile, but easy to construct. Follow these detailed instructions on how to build the stove, and in about two weeks, you’ll be ready to start grilling, cooking, baking and smoking.
Choosing the right location for your stove is important for convenience and optimizing its use. Putting it near your indoor kitchen will save lots of steps, but consider the direction of prevailing breezes so smoke doesn’t blow toward your house or outdoor dining area. Face the stove door downwind for optimum results. Also, consider privacy, ambience, adequate drainage, and space for wood and fire starting supplies. Optional considerations could include adequate space for a cover (highly recommended), dining space, additional countertops and any other extras you might want.
After you’ve selected and cleared your site, build a foundation to support the stove. A low-cost rubble trench foundation is recommended for most situations. The specifics will vary due to climate and soil conditions, but a rubble trench is usually 18 to 24 inches deep and filled with gravel, or gravel and stone. If you’re building the stove in a harsh climate with strong freeze-thaw cycles, add a French drain (a small valley filled with stones) to remove moisture. Raise the building site if necessary to avoid moisture problems.
For our rubble trench foundation, we used chunks of recycled broken concrete, also known as “urbancrete,” instead of stone. Concrete chunks from flatwork slabs, such as sidewalks and driveways, work best. They can be recycled and stacked like stone. Stack these up in layers to the top of the trench. Fill gaps with gravel and then tamp solid.
On top of the rubble trench, pour a 3 1/2-inch by 40-inch by 40-inch concrete pad. This will create a strong, level foundation for your stove. Make sure the pad is level and square. (We poured an entire concrete floor for our outdoor kitchen instead of a just a small leveling pad, but the concept is the same.)
The next step is to build a concrete-block base two courses high with ladder reinforcement (a wire mesh designed to add strength and prevent cracking) between each course. Use 4-inch by 8-inch by 16-inch blocks with a few half blocks as needed. Be sure to lay the block as perfectly plumb, straight and square as possible. Allow to dry for two days or so to gain strength.
Fill the base with gravel or a mixture of sand and gravel. Fill the base with two 6-inch layers, tamping each layer gently. Go easy on the tamping so as not to strain the concrete block joints. All you’re trying to do is settle the materials.
Complete the base by pouring a 4-inch layer of lightweight cement level with the top of the block base. This creates a strong, insulated layer under your firebox. Perlite is perfect for high-heat applications such as this. (According to the Perlite Institute, perlite is used to make gas fireplace logs.) Perlite mix for base: 1 1/3 bags cement, 13 pounds perlite and water. This cement-rich mix is strong enough to support the heavy load of firebricks and countertop, yet also insulate the firebox from the mass below. Let the concrete cure for four to five days.
Firebrick Hearth and Firebox
After about five days, the lightweight concrete should have cured sufficiently and you can begin building the firebox with firebrick. Place a half-inch layer of fine, clean sand on top of the lightweight cement. We screened our own sand (one two-gallon bucket) through fine mesh. Use a straight edge to make it as level as possible. Precise leveling is a critical step that determines the accuracy of the firebox.
The first layer of firebrick creates the hearth. Standard firebrick size is 2 1/2 inches by 4 1/2 inches by 9 inches. The front row of firebricks is perpendicular to the other firebricks and extends 2 inches beyond the concrete block. This makes it easy to sweep coals and ashes into a bucket. We added half-inch concrete board shims under the front edge for stability, where sand would fall away.
All firebricks are placed without mortar so they are free to expand and contract. The placement technique involves carefully sliding each firebrick straight down — one against the other — into place to avoid gaps. After the first course is set, use the end of your hammer handle to tap on any high spots until all firebricks are flush with each other.
Measure the front of the base and find the center, which should be about 20 inches from either side. Start the first layer of firebricks by placing two bricks on either side of the center of the base, making sure that the brick hang over the front about 2 inches. (The first layer of firebricks should be 8 1/2 inches from the back and 11 inches from the side of the base — if you follow the diagram instead of the photos.)
I made a last-minute decision to lengthen the firebox by 4 1/2 inches (one firebrick width). In hindsight, this probably wasn’t the best choice because now we have minimal insulation on the back of the firebox. My advice is to use one less row of firebricks than shown in the photos. So the hearth will have 14 firebricks, not 16 as shown in the photos. The drawing shows the recommended approach, and the materials list below is based on this smaller firebox.
Continue stacking firebricks for the sides of the firebox. These are stacked on edge as shown. The firebox is easy to build and the bricks can be stacked in about one hour. You may encounter a few firebricks that are not perfectly sized. Buy a few extra so you have spares. It’s important to keep everything plumb, square and level, and all firebricks flush with each other, with no gaps.
If you don’t have experience welding and cutting metal, you might want to have a machine shop make the metal pieces for you. Otherwise, you’ll need a welder and a cutting torch for this step.
At this point, you can put the steel shelf (lintel for chimney) in place. It measures 14 3/4 inches by 18 inches by 1 1/2 inches (the sides are 1 1/2 inches high) and is made of quarter-inch steel. The most important measurement is the inside width, which for our shelf was 14 1/4 inches. This allows firebricks to fit perfectly without being cut. The steel parts are joined with six spot welds: three per side, on the bottom so they don’t interfere with placing the firebrick. With a cutting torch, cut a 6-inch diameter hole in the center for the stovepipe. With the steel shelf in place, flush with each side, set the remaining firebricks in place to form the chimney base.
Concrete Block — Upper Half
To form the outside of the oven, set the remaining two courses of concrete blocks (with ladder reinforcement between courses), being careful not to bump the firebricks. Around the firebox opening (where the concrete blocks meet the firebricks), leave an eighth-inch space to allow for expansion and contraction. We stacked CEBs (compressed earth blocks) temporarily inside the firebox to keep them in place. Bricks would work just as well. Let the block dry for two to three days.
You’ll need a right angle grinder or wet saw to cut a few concrete blocks around the front of the firebox. Both tools will do the job, but my preference is a right angle grinder because of its low cost, ease of use and versatility. (You also might be able to rent one for this project.) We used it to cut CEBs for the wall behind our kitchen, steel reinforcement, tile and concrete blocks. We even used it to grind and sand our wood poles for the cover and to grind the edges of our concrete countertops and griddle. It paid for itself on this one job.
You can now fill the area between the firebox and concrete block with lightweight cement. We used a higher ratio of perlite for this to maximize insulation around the firebox (compressive strength is of less concern on this part). Perlite mix for upper half: two bags cement and slightly less than 26 pounds perlite. (We saved a tiny amount for the insulated door and chimney base.) Allow to dry a few days before proceeding.
The next step is to build the countertop. We chose poured-in-place concrete countertops for their strength, and resistance to heat and moisture damage. For instance, we don’t have to worry if a storm blows some rain into the kitchen. Strength is important so we can clamp a grain grinder to the countertop, an important issue if you’re going to bake healthy breads. Our countertop design holds the firebricks in place. Although hot pads are typically used, we don’t have to worry about setting down hot pans hurriedly or otherwise be overly concerned about damaging the surface. Tile is also very practical, but we used it on the sides of the stove and wanted something different on top. Stone is another good choice, but too expensive for our budget.
We were looking for an inexpensive way to make concrete countertops and came up with a pretty good solution at a fraction of the cost of custom made countertops — about $20 instead of $2,000. (This cost is for 12 1/2 lineal feet of 25 1/2-inch countertops.)
We used 100 percent scrap materials for forming, about a half bag of cement, some quarter-inch rebar, and baling wire, sand, gravel and iron oxide pigment. Forms consisted of leftover eighth-inch cement board and scrap wood. We placed rebar in a grid pattern and then poured concrete on top. Create an eighth-inch space between chimney and countertop with a removable shim to allow for expansion and contraction. As the concrete set up, we used an edging tool to round the edges. Pigment was troweled on the surface as the concrete started to set up. It only takes a tiny amount of pigment sprinkled here and there to create a beautiful color. After the forms were stripped in three days and the edges touched up, we applied a “paint” of iron oxide mixed with water to the edges. You might want to splurge an extra $10 to $20 and add pigment to the entire mix to make integrally colored concrete.
(Full details on building your own cast-in-place concrete countertops will be available in the future.)
Building the chimney is straightforward. There is a damper within easy reach to control air flow and save firewood; open it up when starting fires, and close it down when baking so all the heat doesn’t shoot up the chimney. A cap on top of the stovepipe keeps out rain and snow, and a boot (or collar), along with some silicone, seals the connection on the roof. The stovepipe is in sections to facilitate removal and cleaning. The gap between the stovepipe and chimney base is filled with lightweight cement.
Tile is an excellent finish material that withstands a lot of abuse but also looks beautiful. You can get creative with tile, and it’s a good value. To decide on the color, bring samples home from the store and see what looks best. You might want to choose tile in advance and make slight adjustments to the stove size for a perfect fit. You can tweak sizes of concrete block joints to get tile to fit perfectly and reduce the amount of tile cutting. You can also apply stucco to the concrete blocks or simply paint them.
To apply tile, first scrape the block wall clean of concrete residue. Use a drop cloth to protect the floor. Line up the tile to determine even spacing. Draw a level line around the stove as a guideline for the first row. (We started at the base on the front.) Mix a bucket of mortar, brush water on the back of each tile (or soak tile in water) and trowel on about three-eighths inch of mortar with a pointed trowel. Taper the edges, and lightly press each tile into place. Check for alignment in each direction. A few light taps of your trowel handle will seat the tile firmly in place. Check again for plumb, level, even spacing and to ensure the tile is in the same plane as the stove. It helps to change your angle of view and sight lengthwise along the surface periodically.
Allow the tile to set up a bit and then work grout into the joints with a rubber grout float. Do one section at a time, smoothing the joints and cleaning the surfaces in stages with a sponge. Squeeze out extra moisture from the sponge so the joints aren’t weakened by too much water getting into the grout. Remember to allow an eighth-inch gap between tile and firebricks for expansion and contraction.
All you need to turn your outdoor oven into a smoker is a grill grate (or typical oven grate) about (midheight) in the firebox. Simply drill four holes in the firebrick lining the firebox, insert steel pins in holes and add the shelf. You can also suspend a drip pan from the grate with wire. An oven thermometer is useful for making sure the temperature is right throughout the smoking process.
Grill Grate and Griddle
The outdoor oven uses a grill grate and a griddle of the same size to enable multiple cooking functions. Simply replace one with the other depending on how you’re cooking. For frying, baking or boiling, use the quarter-inch steel griddle. For baking, stack bricks or concrete blocks on top of the griddle to store heat. Another nice feature is adding a grate on the bottom of the firebox to raise pans slightly to improve air circulation and reduce burning. Another optional energy-saving feature is to add a stove gasket to seal the griddle and prevent air leaks.
The door is the key feature needed for baking. We built a 2-inch-thick insulated door of sixteenth-inch steel filled with perlite. This is another firewood saving feature. The front piece of the door forms a lip that hangs over the firebox opening about half an inch to help reduce air leaks. The large wooden handle doesn’t get too hot to touch and enables the door to be installed and removed with one hand. There are no hinges; the door wedges into place. We added an adjustable vent to control airflow and spray painted the door with heat paint. Based on our experience, a 1 3/4-inch hole in the door seems to be the perfect size. If you’d prefer a simpler method for building the door, make a thick hardwood door with a piece of metal on the inside, allowing about a quarter-inch air gap between wood and metal. You could rabbet the edges for a tighter seal. Also, a thermometer built into the door would be a nice feature.
Fire It Up!
Wait a few days for the tile to cure before firing up the stove for the first time. We started with a small fire and gradually, one fire per day, built increasingly larger fires in order to drive out any remaining moisture.
The Fastest Way to Start a Fire
Place two 2-inch-diameter pieces of firewood in each side of the firebox. Add crumpled newspaper between and place dry sticks on top of the newspaper across the 2-inch pieces of firewood. Add more twigs (up to the size of your little finger) on top in a crisscross pattern. Avoid placing too much wood at first to allow good airflow. Have everything ready before lighting the fire: small split kindling and 1- to 2-inch pieces of firewood or charcoal.
Open the damper and the vent hole in the door. A lit candle can help start the fire quickly. Add kindling after three to four minutes when twigs are solidly ablaze. Add larger pieces after about 5 minutes. Wait 5 minutes and close both the damper and vent holes halfway.
Tips for Using the Outdoor Oven
- Mop the hearth with a damp rag on a stick to create steam for improving certain breads.
- Best types of wood to use: pecan and cherry (too much hickory or mesquite can make food bitter). Apple works well, too, but you’ll have to find what’s available in your area.
- Cook from the side so you’re not standing directly in front of the firebox (this is more comfortable).
- The stove can heat up to 400 degrees in as little as 15 to 20 minutes, depending on how the fire is built. Some may prefer to wait and let the firebrick store up more heat, but you could start cooking right away.
- A covered baking dish works perfectly for making bread. It keeps moisture inside the container, which turns to steam and creates light, spongy, moist bread with maximum loft.
- We keep a small fire burning in the back of the firebox while baking. This maintains steady heat and enables us to bake and grill multiple items. Reposition (turn) food occasionally to prevent burning.
- Cover desserts with tin foil or a lid to prevent unwanted smoke flavor. The same flavoring that makes grilled food taste so great can really ruin the taste of desserts.
- When finished cooking, the last step is to scoop out coals and douse them with water. We use homemade charcoal, which means it can be reused again when dry.
- Our cheap oven thermometer was obscured with smoke after just a few uses. (The smoke got inside the thermometer.) A good thermometer should last much longer. The best method is probably to add a thermometer in the door. This makes it easy to check the interior temperature without opening the door (which lets a lot of heat out very quickly).
A bench brush (with natural bristles, not plastic) is very convenient for sweeping out ashes in the front of the stove. To prevent burning the bristles, first remove coals with a scoop. A whisk broom also works well.
No line-drawing plans exist for this project. The diagram and materials list are all we have for this one.
Here's a tip, though. The diagram show a cut-through version of the oven that precisely splits the oven in half. So where you see two firebricks in the front of the oven floor, the total will be four across the front.
Engineer/contractor Owen Geiger is the co-developer of earthbagbuilding.com and often uses natural building materials.