Fire Features

PROTECT YOUR INVESTMENT:fire features

Before long, one of your favorite pastimes will be spending time next to a warm and cozy fire feature. Here are a few tips and guidelines for proper use of your new fire pit or fireplace.

Expansion and contraction

It is natural and common knowledge that heat causes materials like metal, soil, glass, wood, stone and concrete to expand, contract, warp, melt, change shape, etc. If your fire pit or outdoor fireplace expands and contracts, it can cause hairline cracks in the exterior veneer that are cosmetic and not structural failures of the feature. Expansion cracks most commonly appear in the mortar joints, normally in the area that endures the highest heat and is closest to where the fire burns.

Effect of moisture

Concrete/stone, moisture and heat do not work well together. Heat and moisture create steam and steam has the ability to move the concrete/stone and an overabundance can cause damage. Concrete and stone from your fire pit or outdoor fireplace will absorb moisture from rain, snow, human watering and even moist, humid air. It is recommended that you wait 28 days after construction to use your fire pit or fireplace, allowing the mortar joints and exterior veneer ample time to cure. If your fire pit or outdoor fireplace is going to be used after being exposed to moisture, start a small fire and heat the appliance up slowly and avoid large fires until the unit has had ample opportunity to dry from the inside out. This may take several hours depending on the amount of moisture the unit has been exposed to; plan accordingly when you intend to use your feature.

Thermal cycling

Thermal cycling is a process of alternatively cooling and heating material. This enhances the strength and performance of materials thereby improving the longevity and stress bearing qualities. This process induces what is known as molecular reorganization, optimizing a material’s molecular structure and making it denser and more uniform. The process involves heating the part repeatedly and then allowing it to return to ambient temperature. In short, your fire pit or outdoor fireplace will gain strength with every use, but it’s important to start carefully with small, shorter length burns. The ground breaking of your feature should NOT be a large, grand fire that your run for hours. If you are planning a christening party for your outdoor living space, be sure to have a few small, short fires in the days leading up to your gathering.

Effects of cold temperatures

When the ambient temperature of your fire pit or outdoor fireplace is 40 degrees and below, special consideration should be taken. Heating a concrete or stone appliance too quickly no matter what the ambient temperature can cause damage, but is much more likely when the feature is below 40 degrees. The colder the ambient temperature, the more cautious you should be when building a fire. This is not to say that you cannot use your fire pit or outdoor fireplace in cold temperatures. It is recommended that you build a small fire in the beginning and heat the appliance slowly until it reaches normal operating temperatures. Be sure to plan accordingly because this may take hours, depending on the temperature.

Over firing, accelerants and extinguishing

Even though fire pits and outdoor fireplaces are made of heat tolerant refractory materials, they can be damaged from over firing. All materials have their limitations on the amount of heat they can endure and can be damaged if they are operated beyond those limitations. Always burn a fire in the center of the feature on a log grate and away from the walls. Do not let logs lean against the walls of your feature; the intense heat could cause cracking while in use or during the cooling process. To prevent over firing, never burn more wood at one time than the log grate is capable of holding. USE COMMON SENSE. Never use accelerants like gasoline, alcohol, oil or any liquid to light or enhance the size of a fire. This could severely damage the fire feature and also creates the risk of an explosion and bodily harm. NEVER extinguish a fire using water, liquid or any suppressant that would create an immediate temperature contrast; this can and will cause cracking of stone, mortar and concrete.

Additional safety precautions

A fire pit or outdoor fireplace can bring many hours of enjoyment, comfort and warmth if operated and maintained properly. Certain safety precautions must be observed to eliminate the dangers associated with fire and provide a satisfactory, smoke free fire.

  1. When burning wood, use solid, seasoned wood only. Do not use scrap wood, artificial wax-based logs, treated wood, coal or woods dipped in pine tar or pitch.
  2. Never use gasoline or other combustible liquids when starting a fire.
  3. Keep combustible furniture, pillows, blankets etc. at least four feet from the opening.
  4. Never leave unattended.

Be extremely careful when adding wood and handling fireplace tools. Never throw, kick or by any other means force wood into the firebox as this could damage the firebrick and walls, resulting in permanent damage and void the warranty. Stress cracks created from thermal cycling are normal.

Selection of wood

USE CURED WOOD LOGS: Use cured wood logs only. Scrap wood produces sparks. Treated wood, coal or woods dipped in pine tar should not be used because they may leave a combustible residue in the fireplace and chimney. Use of seasoned wood is preferred.

SOFTWOOD VS. HARDWOOD: Wood is divided into two classes, hard and soft woods. Each has a use in a fireplace and each has advantages and disadvantages.The hardwood category includes such woods as oak, walnut, birch, elm and maple. Softwoods include pine, fir, cedar and spruce.

Selection of wood depends on the type of fire you want. Softwoods are good to offset a morning chill because the fire develops faster. Hardwoods are preferable for a slower burning and uniform heat output.

Softwoods contain a highly flammable resin that will leave creosote soot in the chimney flu. This often results in sparking. Burning softwood exclusively will require more frequent inspection and cleaning of the chimney.

Experienced fire builders will often use small amounts of softwood kindling and newspaper when starting a split hardwood log fire.

SEASONED WOOD: Most freshly cut “green” wood will not burn well and will smoke. The pressure of moisture and resin inside green wood will build under heat and explode as sparks. Therefore, it is recommended that only seasoned wood be used in your fireplace.

Most wood requires 9-12 months of seasoning and drying to reduce the moisture content enough to produce good steady fires. Make sure that you buy only seasoned wood, or if you buy green wood (usually cheaper), store it properly to aid in the seasoning process. The following steps will assist in the seasoning process.

  1. Stack wood loosely to permit maximum air circulation.
  2. Do not stack wood on the ground. Use a wood rack or stack on scrap lumber. Storage on the ground will cause rotting and insect infiltration.
  3. Cover wood stacks with a tarp so that it is not excessively exposed to the elements such as snow and rain.
  4. Do not stack wood against the walls of your home.

Building a fire

  1. Use a log grate with your fire pit or outdoor fireplace when burning wood. This will contribute to good air circulation around the wood and keep the wood out of the ash.
  2. Remove any excess ash from the fire pit or outdoor fireplace. Excessive ash may reduce airflow. Some owners prefer to leave a small layer to insulate the cold refractory below the grade, helping fire starting.
  3. Center the log grate in the firebox.
  4. Crumble several newspapers across the fire area underneath the grate. Criss-cross kindling wood on top of the grate, above the newspaper.
  5. Lay three logs on the grate; two side by side and the third in pyramid fashion on top. Split longs will start faster. Make sure there is space between the logs for air circulation. As the air is heated, it is drawn upwards through the space between the logs, creating more combustion.
  6. Light the paper at both sides of the firebox.
  7. Make sure the fire remains centered in the firebox. Don’t let it move to the front or sides. Move it back with a poker.
  8. Add more wood to the fire as necessary.

 

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Thomas Welker

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