When constructing an outdoor fire pit, one of the most important decisions is choosing the right mortar. The mortar is responsible for binding and securing the firebricks or other masonry materials used to build the fire pit walls. Selecting a mortar that can withstand high temperatures is crucial for safety and longevity of the fire pit.
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Types of Mortar for Fire Pits
There are several types of mortar that can be used when building an outdoor fire pit:
- Fireclay mortar – This refractory mortar is specifically designed for high heat applications like fire pits and chimneys. It is composed of fire clay and sand and can withstand temperatures up to 3000°F.
- Masonry cement mortar – A blend of portland cement, lime, and sand, this general purpose mortar has high compressive strength. It can withstand temperatures up to 2000°F.
- Refractory mortar – Contains heat resistant aggregates like fire clay or perlite. Can withstand heat up to 2500°F.
- Sairset mortar – A proprietary premixed mortar for masonry joints. Withstands up to 2012°F.
Of these options, fireclay mortar is the best choice for outdoor fire pits. It is designed specifically for high temperature applications and will be the most durable option. Masonry cement or refractory mortars are acceptable alternatives.
Properties to Look for in Fire Pit Mortar
When selecting a mortar product, there are a few specific properties to evaluate:
- High heat tolerance – The mortar should be rated for temperatures of 2000°F or higher. This ensures it can withstand the heat of a roaring fire pit.
- Low shrinkage – Mortar that resists shrinkage will help maintain tight joints and prevent cracking that allows heat or embers to escape.
- Good adhesion – Strong bond to firebricks and other masonry is needed to hold up over time.
- Workability – The mortar should be fairly easy to mix, apply, and tool for faster construction.
- Outdoor durability – Resistance to weathering damage from rain, snow, and freeze/thaw cycles.
Fireclay mortar offers the best all-around performance in these areas compared to other types of mortar.
Mixing Fire Pit Mortar
It is important to properly mix and prepare mortar before applying it to the fire pit construction. Here are some tips:
- Wear safety gear like gloves, goggles, mask to avoid contact with skin and eyes.
- Follow the manufacturer’s mixing instructions for ratios of mortar, water, and any other additives.
- Mix it thoroughly until it forms a workable, lump-free consistency.
- Only mix up as much as can be used in 30-60 minutes before it starts to set.
- Retemper partially set mortar by adding water to bring back to a workable consistency.
Test the finished mortar mix by forming a ball and letting it drop on a hard surface. It should crack, not shatter. Mortar that is too dry will be crumbly while mortar that is too wet will not adhere properly.
Installing Mortar for Fire Pits
Once mixed, mortar can be installed to set firebricks or other masonry materials:
- Apply even 1/4 to 1/2 inch layer of mortar onto base material or firebrick.
- Set next firebrick or masonry piece while mortar is still workable.
- Push down firmly and wiggle slightly to work mortar into joints.
- Strike flush exterior joints with trowel for smooth finish.
- Allow mortar to cure for at least 72 hours before lighting first fire.
Take care to keep exterior mortar joints neat for best appearance. Cover completed work with plastic if rain is expected before mortar has set.
Benefits of Using Proper Fire Pit Mortar
Utilizing a high quality, heat resistant mortar product for fire pit construction offers many benefits:
- Withstands heat – Won’t break down or crumble when exposed to high temperatures from fire.
- Reduces cracking – Minimizes joint cracks that compromise fire containment.
- Improves durability – Provides a stronger bond and withstands damage from normal weathering.
- Prevents leaks – Seals joints tightly reducing smoke and ember escape.
- Lengthens lifespan – Fireclay mortar used properly can last for decades.
Choosing the optimal fire pit mortar gives peace of mind that the fire pit structure will hold up safely for many seasons of enjoyable backyard fires to come.
Fire Pit Mortar Safety Tips
When working with mortar products, follow these important safety practices:
- Read and follow label directions for preparation, mixing, and use.
- Wear eye protection and waterproof gloves when handling dry and mixed mortar.
- Avoid skin contact with mortar by covering exposed skin.
- Do not allow mortar to dry on skin, wash off immediately with water.
- Wear a dust mask when handling powdered mortar materials.
- Clean tools after use before mortar dries.
- Store mortar materials properly sealed and out of the reach of children.
Mortar contains caustic ingredients like cement and lime that can cause skin and eye irritation. Taking appropriate precautions will prevent painful injuries.
Conclusion
Constructing a safe, long-lasting outdoor fire pit requires the proper selection and application of high temperature mortar. Fireclay mortar is specifically designed for the demands of fire pit construction. With a heat tolerance over 3000°F, excellent adhesion, and weather resistance, it provides optimal performance and longevity.
Taking care to mix and install fireclay mortar according to manufacturer specifications will create durable mortar joints that withstand cracking under heat stress. Proper use of fire pit mortar along with general construction safety principles will result in an outdoor fire pit that can be enjoyed for many years to come.
| Mortar Type | Heat Tolerance | Good Adhesion? | Weather Resistant? |
|---|---|---|---|
| Fireclay Mortar | 3000°F+ | Yes | Yes |
| Masonry Cement | 2000°F | Moderate | Fair |
| Refractory Mortar | 2500°F | Yes | Moderate |
| Sairset Mortar | 2012°F | Yes | Good |
This table summarizes key performance factors for common fire pit mortar types. Fireclay mortar consistently rates highest in the important properties of heat tolerance, bond strength, and weather resistance.