Pizza Oven Building Guide
How to Make High-Temperature Mortar
The classic 4-ingredient firebrick mortar for wood-fired pizza ovens, made from silica sand, hydrated lime, fire clay and Portland cement. Here's the recipe, how to mix and lay it, and the substitutions that cause trouble.
Quick Answers
- The recipe is 3 parts silica sand, 1 part hydrated lime, 1 part fire clay and 1 part Portland cement, measured by volume.
- Dry-mix until the color is even, then add water a little at a time until it's firm and buttery, like thick peanut butter.
- Use it between firebricks wherever the fire touches brick. Don't use it under the oven floor bricks, as a castable or for the outer shell.
- Let it cure about a week, then start with small curing fires that grow gradually.
- All four ingredients are sold at landscape & masonry supply stores, usually for far less than shipping them.
The Recipe
The 3:1:1:1 High-Temperature Mortar Recipe
This is the classic homemade high-temperature mortar used to lay firebrick in wood-fired pizza ovens and fireplaces around the world. BrickWood didn't invent it. It's been around for decades, and it's the recipe we've recommended for thousands of DIY ovens because it's inexpensive, forgiving and made from four materials you can buy locally.
The 3 : 1 : 1 : 1 Mix (by volume)
Measure by volume, not weight. Lime is fluffy and weighs far less per scoop than sand, so weighing the ingredients throws the recipe off.
What Each Ingredient Does
| Ingredient | Parts | Its job in the mortar | Where to find it |
|---|---|---|---|
| Silica Sand | 3 | The body of the mortar. Fine grains pack tightly around the three powders. | Pool supply, landscape & masonry supply |
| Hydrated Lime | 1 | Makes the mix creamy and workable, slows the set so you get more working time, and helps the mortar shed water. | Landscape & masonry supply, plant nursery |
| Fire Clay | 1 | The heat-resistant ingredient. It's the same type of clay used to make firebrick. | Landscape & masonry supply, ceramic supply |
| Portland Cement | 1 | Gives the mortar its first set and early strength, so each course holds while you keep building. | Every home improvement store |
What You'll Need
- Wheelbarrow or mixing tub, and a hoe or square shovel
- One measuring scoop (bucket, coffee can or shovel) used for every ingredient
- Clean water and a bucket for dampening the firebrick
- Brick trowel and a damp sponge
- Dust mask (N95 or better), safety glasses and waterproof gloves
Step by Step
- Gear upWear a dust mask (N95 or better), safety glasses and gloves. Dry cement, lime and fine silica are dusty and caustic, so mix outdoors or in a well-ventilated space.
- Measure by volumeUse one scoop for everything (a bucket, a coffee can or a shovel): 3 scoops of sand, 1 of lime, 1 of fire clay and 1 of Portland cement. Level each scoop.
- Dry-mix firstBlend the dry ingredients in a clean wheelbarrow or mixing tub until the color is even, with no streaks of white lime or clay. This step prevents most homemade-mortar problems.
- Add water a little at a timeMix to a firm, buttery consistency, about like thick peanut butter. It should hold its shape on a tilted trowel, not slump or run. Add enough water to blend, but keep it firm.
- Mix small batchesMake only what you can lay in about an hour. If a batch starts to set up in the wheelbarrow, throw it out rather than adding water to revive it.
- Dampen the firebrickDry firebrick pulls water out of the mortar and weakens the bond. Dip or hose the bricks, then let the surface water soak in so they're damp, not dripping.
- Butter, set and clean upButter the brick faces, press each brick into place and keep the joints thin and full. Scrape off squeeze-out with the trowel, then wipe lightly with a damp sponge once it firms up.
- Cure, then fire slowlyLet the mortar cure for about a week, then follow your oven's curing-fire schedule: small fires that grow gradually. A big fire on wet mortar makes steam, and steam cracks joints.
Where to Use It (and Where Not To)
- Use it between firebricks anywhere the fire touches brick: the walls, the vault or dome, the back wall and the oven opening.
- Don't use it under or between the oven floor bricks. Hearth bricks are laid dry on a level bed and held in place by the brick frame around them.
- Don't use it as a castable. This recipe is a mortar only. No matter what you see online, it can't be poured or cast into oven shapes.
- Don't use it for the outer shell. Over the insulation, use regular Type S mortar or stucco. It costs less and is made for that job.
Don't Change the Recipe
- No Type S or Type N mortar mix, masonry cement or Portland cement with lime already blended in. They already contain sand and lime in the wrong ratio.
- No premixed "fireclay" from a pail. That's refractory mortar, not fire clay, and it won't blend with the other three ingredients.
- No granulated garden lime, and no play, all-purpose, mason or concrete sand.
- No extra additives. Just silica sand, lime, fire clay and Portland cement.
How Much Do I Need?
Your oven's materials list tells you how much high-temperature mortar to plan for. The recipe is 6 parts total, so half of every batch is sand and the other half is split evenly between lime, fire clay and Portland cement. If this is your first brick project, buy about 15% extra to cover a bad batch or two.
Rather skip the mixing? A dry, bagged, non-water-soluble refractory mortar is a just-add-water alternative. For brick ovens, never use a premixed high-heat mortar from a bucket or pail. If it is water-soluble, rain will wash out the joints over time.
Choosing the Right Ingredients
Almost every homemade-mortar problem we hear about starts at the store, when a look-alike product ends up in the wheelbarrow. Each ingredient has its own guide with photos of what to look for, but here's the short list.
| Ingredient | Buy this | Not this |
|---|---|---|
| Silica Sand | ✓ Pool filter sand or fine silica sand (any grit from about 30 to 90) | ✗ Play sand, all-purpose, mason, concrete or beach sand |
| Hydrated Lime | ✓ Type S (or Type N) hydrated lime, a white powder like powdered sugar | ✗ Garden lime pellets, ground limestone, quicklime, hydraulic lime |
| Fire Clay | ✓ Mid-fire or high-fire clay, mortar clay or brick mason's clay, as a dry powder | ✗ Premixed "fireclay" in a pail, moist pottery clay, low-fire clay |
| Portland Cement | ✓ Plain Portland cement, Type I, II or I/II | ✗ Mortar mix, masonry cement, Portland-lime blends, concrete mix |
Find These Materials in Your Area
Buy local first and save on freight.
All four ingredients are heavy, inexpensive and stocked at stores near you. Shipping a 50-lb bag across the country can cost more than the bag itself, so check these places before you order anything online.
Call ahead and ask for each item by the names on this page. Counter staff sometimes suggest a premixed substitute that doesn't belong in a wood-fired oven.
Why Regular Mortar Isn't Enough
Regular masonry mortar, like the Type S or Type N mix sold at hardware stores, is made of sand, Portland cement and lime. It's the right choice for a block base, a brick frame around the hearth and the stucco shell over your insulation. It isn't made for the inside of a wood-fired oven.
Ordinary Portland cement paste starts to lose strength once it gets much past about 570°F (300°C), and a pizza oven runs far hotter. High-temperature mortar keeps the Portland cement for its early set, adds more lime, and adds fire clay, the same kind of clay used to make firebrick. The result is a mortar that heats, expands and cools much like the brick around it, fire after fire.
| Mix (by volume) | Sand | Portland | Lime | Fire clay | Use it for |
|---|---|---|---|---|---|
| Type N mortar | 6 | 1 | 1 | 0 | General masonry |
| Type S mortar | 4½ | 1 | ½ | 0 | Block base, hearth frame, outer shell |
| High-temperature mortar | 3 | 1 | 1 | 1 | Firebrick joints inside the oven |
A sales rep's job is to sell what the store stocks, and some will tell you a bag of Type S mortar "already has everything in it." It doesn't have fire clay, and its ratio is wrong for an oven. Buy the four ingredients separately.
Homemade vs. Factory Refractory Mortar
You have two good options for the firebrick joints in a wood-fired oven: mix the 4-ingredient recipe yourself, or buy a factory-blended refractory mortar. Both work. The one product to avoid is premixed high-heat mortar from a bucket or pail.
| Homemade 3:1:1:1 | Dry, bagged refractory mortar | Premixed mortar in a pail | |
|---|---|---|---|
| What it is | Sand, lime, fire clay and Portland cement you mix yourself | A factory dry blend; just add water | Ready-to-use wet mortar |
| Cost | Lowest, especially bought locally | Higher | Higher |
| Ease of use | Forgiving, but you have to measure and mix carefully | Very hard to get wrong | Easy |
| Weather resistance | Good for outdoor ovens | Choose a non-water-soluble product | Many are water-soluble and can wash out of outdoor joints |
| Brick ovens like the Mattone Barile | ✓ Yes | ✓ Yes | ✗ No |
Prefer the just-add-water route? Our refractory mortar is a dry, non-water-soluble blend made for outdoor ovens. If you buy a different brand, call the manufacturer and confirm it's non-water-soluble before you use it outdoors.
What Does It Cost? Homemade vs. Refractory Mortar
Making your own high-temperature mortar costs a fraction of buying refractory mortar. How big a fraction depends on where you buy the refractory mortar.
Why refractory mortar prices vary so much. Most local landscape and masonry stores don't stock refractory mortar by the pallet. They buy a few bags at a time from a nearby refractory manufacturer or distributor. That means they pay small-order pricing, freight, and often a "broken pallet" fee for not buying a full pallet. Then they add their own markup. By the time the bag reaches you, it can cost a lot. We've heard of builders paying around $150 for a 50-lb bag.
For the lowest price, buy directly from a refractory manufacturer or dealer. You'll usually pay about half what a landscape supply store charges, often around $60 for a 50-lb bag. See our list of refractory dealers near you.
What the homemade recipe costs. All four ingredients are stocked at landscape and masonry supply stores, and they're inexpensive:
| Ingredient | Bags | Price per 50-lb bag | Cost |
|---|---|---|---|
| Silica sand | 3 | $12 | $36 |
| Portland cement | 1 | $13 | $13 |
| Hydrated lime | 1 | $12 | $12 |
| Fire clay | 1 | $22 | $22 |
| Total | 6 bags (300 lbs) | $83 |
Side by side: 300 lbs of high-temperature mortar
| Price per 50-lb bag | 300 lbs (6 bags) | Cost per pound | |
|---|---|---|---|
| Homemade 3:1:1:1 | About $14 average | $83 | About $0.28 |
| Refractory mortar, direct from a manufacturer | About $60 | $360 | About $1.20 |
| Refractory mortar, local landscape store | $120 to $150 | $720 to $900 | $2.40 to $3.00 |
Even compared with the best refractory mortar price, mixing your own saves about $277 (roughly 77%). Compared with a local landscape store, the savings can run $600 to $800 or more.
Prices are estimated 2027 averages and vary by region.
Refractory Mortar Has a Short Shelf Life
Bagged refractory mortar keeps for about a year or less, and less if the bag gets damp. Buy it when you're ready to build, not months ahead, and don't plan to save leftover bags for a future project. Whichever mortar you choose, store the bags off the ground and keep them dry until you mix.
This Recipe Is a Mortar Only
- No matter what you read online or watch on YouTube, the 3:1:1:1 recipe can't be used as a homemade castable refractory. For a cast oven dome, use a real castable refractory cement.
Cracks and Other Problems
| Problem | Likely cause | What to do |
|---|---|---|
| Mortar won't stick to the brick | Bricks too dry, or mix too wet | Dampen the bricks first and stiffen the mix with a little more dry blend |
| Mortar sets up before you can use it | Batch too big, hot day, or too little lime | Mix smaller batches, work in the shade, and keep lime at 1 full part |
| Crumbly, sandy joints | Not dry-mixed well, wrong sand, or a look-alike product | Check each bag against the ingredient guides and dry-mix until the color is even |
| Big cracks after the first fires | Fired too hot, too soon, before the mortar dried | Follow the curing schedule with small fires that grow day by day |
| Fine hairline cracks | Normal heating and cooling of a masonry oven | Usually cosmetic. Insulation and the outer shell keep the heat in |
Insulation matters as much as mortar. Wrap the cured firebrick in 2 layers of ceramic fiber blanket before the outer shell goes on, so the oven holds its heat and the outside stays cool.
High-Temperature Mortar FAQ
What is the recipe for high-temperature mortar?
3 parts silica sand, 1 part hydrated lime, 1 part fire clay and 1 part Portland cement, measured by volume. Dry-mix them, then add water until the mortar is firm and buttery.
Is the 3:1:1:1 ratio by weight or by volume?
By volume. Use the same scoop for every ingredient. Lime is much lighter than sand, so measuring by weight throws the recipe off.
How much water do I add?
Add it a little at a time until the mortar is firm and buttery, about like thick peanut butter. It should hold its shape on a tilted trowel without slumping. Add enough water to blend, but keep it firm.
Can I use Type S mortar in a pizza oven?
Not for the firebrick joints. Type S mortar has no fire clay and isn't made for oven temperatures. It is the right mortar for the block base, the hearth frame and the outer stucco shell.
Do I mortar the oven floor bricks?
No. The hearth (floor) bricks are laid dry on a level bed of all-purpose sand and held in place by the brick frame around them. Use high-temperature mortar only where the fire touches the walls and vault.
Can I use this recipe as a castable refractory?
No. The 3:1:1:1 recipe is a mortar only. A cast dome needs a real castable refractory cement.
Should I wet the firebrick before mortaring?
Yes. Dry firebrick pulls water out of the mortar and weakens the bond. Dip or hose the bricks, then let the surface water soak in so they're damp, not dripping, when you lay them.
How long should high-temperature mortar cure before the first fire?
About a week. Then follow your oven's curing-fire schedule, starting with small fires that grow gradually. A big fire on wet mortar makes steam, which cracks joints.
Where do I buy the ingredients?
A landscape & masonry supply store usually carries all four. Pool supply stores sell pool filter sand, ceramic suppliers carry fire clay, and every home improvement store carries Portland cement.
Is homemade high-temperature mortar as good as factory refractory mortar?
For a backyard wood-fired oven, yes. It's inexpensive, forgiving and used around the world. A dry, bagged, non-water-soluble refractory mortar is a good just-add-water alternative. Avoid premixed mortar from a pail for brick ovens.
Is it cheaper to make high-temperature mortar than to buy refractory mortar?
Yes. Six 50-lb bags of the 3:1:1:1 ingredients cost about $83, or roughly $0.28 per pound. Refractory mortar runs about $1.20 per pound bought direct from a manufacturer, and $2.40 to $3.00 per pound at many local landscape stores. See the cost comparison.
Ingredient Guides and Next Steps
Building a wood-fired pizza oven?
Our FREE plans include the full materials list, so you'll know exactly how much mortar to mix.
BrickWood has helped thousands of backyard builders since 2013. Ask a question on our forum and you'll get an answer from people who have built the same oven.
Store availability and prices vary by region. Always follow the safety information printed on each bag.
