High-Temperature Mortar Ingredient
Silica Sand for High-Temperature Mortar
Sand makes up half of every batch of high-temperature mortar, so the type you use matters. Here's which sand to use, which sands to avoid, and the easiest place to find the right one.
Quick Answers
- Use fine silica sand. Pool filter sand is fine silica sand and is the easiest to find.
- The finer the grain, the better the bond. Any grit from about 30 to 90 works.
- Don't use play sand, all-purpose sand, mason or mortar sand, concrete sand or beach sand.
- Sand is 3 parts of 6 in the recipe: 3 sand, 1 lime, 1 fire clay, 1 Portland cement, by volume.
What Is Silica Sand?
Industrial silica sand is sand made up of almost pure quartz grains, washed and screened to a consistent size. It looks clean and light-colored and feels almost like powder in the finest grades. Pool filter sand is graded silica sand, which is why pool supply stores are the easiest place to buy it.
Why Fine Sand Matters in High-Temperature Mortar
All sand contains some silica, but fine-grain sand is what you want for high-temperature mortar. Fine grains are 3 to 6 times smaller than coarse grains, so they blend and bond better with the other three ingredients, which are all fine powders. The finer the sand, the stronger the bond.
Clean silica sand is also consistent. General-purpose sands can carry bits of rock, clay, shell or other minerals that behave differently from firebrick when they're heated and cooled again and again.
Which grit size?
Sand grit works like sandpaper: the bigger the number, the finer the grain. Dealers commonly carry about 30 to 90 grit, and all of them are fine for high-temperature mortar. Once the four ingredients are mixed, it's hard to see any difference between them.
How Silica Sand Is Used in High-Temperature Mortar
Silica sand is 3 parts of every 6, half of the mix. Its fine grains pack tightly around the three powders and give the mortar its body.
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.
The short version: dry-mix all four ingredients by volume until the color is even, then add water a little at a time until the mortar is firm and buttery, like thick peanut butter. Dampen your firebrick, lay thin, full joints, and let the mortar cure for about a week before your first small curing fire.
Our full guide covers every step, the tools you need, where to use the mortar (and where not to), and how it compares to factory-made refractory mortar.
Sands to Use and Sands to Avoid
This is the question we get most. The short answer: only fine silica sand goes in high-temperature mortar. Pool filter sand is the easiest kind to find. Every other sand on the shelf, including play sand and mason sand, stays out of the mortar.
Use Only These
- Pool filter sandFine silica sand, sold at almost every pool supply store
- Fine silica sandAny mesh or grit size
- Fine sandOnly when the bag actually says "fine"
The finer the grain, the better.
Never Use These Sands
- Play sandMade for sandboxes. Grain size and makeup vary from brand to brand, so you can't count on it.
- All-purpose / multi-purpose sandA coarse blend for bases and leveling. It's the right sand under your hearth bricks, not in your mortar.
- Mason sand / mortar sandGraded for everyday brick mortar, not a fine, uniform silica sand.
- Concrete, coarse or medium sandThe grains are too large to bond well with the fine powders.
- Natural sand / sand toppingUnscreened, with mixed minerals and debris.
- Beach or sea sandCarries salt and shell fragments.
Rule of thumb: if the bag doesn't say pool filter sand, silica sand or fine sand, keep it out of your mortar.
Two Sands, Two Jobs
A brick pizza oven uses two different sands, and mixing them up is one of the most common questions we get.
| Where | Sand to use | Why |
|---|---|---|
| High-temperature mortar | Fine silica sand or pool filter sand | Fine grains bond tightly with the fire clay, lime and Portland cement |
| Leveling bed under the hearth bricks | All-purpose sand (not silica sand) | The coarser blend lets you nudge each floor brick into place and keeps it from locking up while you level |
Fine silica sand is dusty. Breathing crystalline silica dust over time can cause serious lung disease, so wear an N95 or better dust mask when you pour and mix, and work outdoors.
Find These Materials in Your Area
Need it today? Check a store near you.
We ship every bag FREE to the contiguous United States. If you would rather pick it up today, all four ingredients are stocked at stores near you, so check these places first.
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.
Silica Sand FAQ
What kind of sand do I use for high-temperature mortar?
Fine silica sand. Pool filter sand is fine silica sand and is sold at almost every pool supply store. The finer the grain, the better the bond.
Is pool filter sand the same as silica sand?
Yes. Pool filter sand is graded silica sand, and it's the easiest way to get fine silica sand for mortar.
Can I use play sand in high-temperature mortar?
We don't recommend it. Play sand is made for sandboxes, and its grain size and makeup vary from brand to brand. Use pool filter sand or fine silica sand instead.
Can I use all-purpose sand?
Not in the mortar. All-purpose sand is the right choice for the leveling bed under your hearth bricks, but it's too coarse for high-temperature mortar.
Can I use mason sand or mortar sand?
Not for this recipe. Mason sand is graded for everyday brick mortar. High-temperature mortar needs fine, uniform silica sand.
What grit silica sand should I buy?
Anything from about 30 to 90 grit works. Like sandpaper, a higher number means a finer grain.
How much sand is in high-temperature mortar?
Half of it. The recipe is 3 parts silica sand to 1 part each of hydrated lime, fire clay and Portland cement, measured by volume.
Please Order Carefully: Refractory Materials Are Non-Refundable Once Shipped
Refractory materials are heavy, costly to ship and can't be resold once they leave our warehouse. For that reason, refractory products can't be cancelled, returned or refunded once your order has shipped.
We're happy to help you get it right the first time. If you're not sure which product or how much you need, contact us before you order and we'll walk you through it.
Shipping
FREE shipping on every refractory product to all locations in the contiguous United States (the lower 48 states). Orders ship by ground carrier or commercial freight, depending on size, and freight carriers will call to schedule delivery. Please leave a phone number we can reach you at in the order notes.
Keep Building
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.
Store availability and prices vary by region. Always follow the safety information printed on each bag.
