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What is Pressure Treatment?

Pressure treatment is a carefully controlled process of pressure and vacuum cycles within an enclosed cylinder. The process forces preservatives deep into the cellular structure of the wood, forming a chemical bond that resists decay and attack by insects. This bonding process, known as “fixation,” locks the preservative into the wood, making it highly resistant to leaching or dissolving.

How Wood is Pressure Treated

What preservatives are used?

The most commonly used preservatives for treating wood for residential use are MCA, CA, and Borate. Over a million decks and countless other outdoor structures are built each year using Southern Pine wood that has been treated with these preservatives.

WHAT TYPE OF PRESSURE TREATED WOOD SHOULD I USE?

Culpeper offers a number of different treatments for multiple applications.  By reading the end tag on each piece of wood, the end user will be able to determine if a product is approved for “Above Ground” use or “Ground Contact” use.  It is very important to use the proper use for the intended application.

For more on treatment standards click here.

Choosing the Right Culpeper Pressure Treated Lumber for your Project

WHAT DOES “GROUND CONTACT” MEAN?

Ground contact means that the product is approved for use in applications that require direct contact with the ground. This includes any applications where it will need to be used in the ground such as posts for fences or decks.

LOOKING AT SOME BOARDS, THE MIDDLE LOOKS LIKE IT HASN’T BEEN TREATED. WHY IS THIS?

You are seeing what is called the heartwood of the tree which is naturally decay resistant.  This is no indication the wood was improperly treated.  Due to the vacuum process in our chemical treating plants, you can be assured the wood has been treated according to treated standards.

IS MCA PRESSURE TREATED WOOD SAFE?

CULPEPER MICROPRO is perfectly safe. You can play barefoot on it, build garden beds out of it, lie out in the sun on it, or eat a picnic on it. Treated lumber is a nontoxic product that only frustrates termites and fungus. Like many chemical substances that require special handling, these preservatives have regulations for use established by the EPA. It can only be sold to certified wood treatment facilities. The EPA’s regulations apply only to the chemicals, not to the finished product. Once these preservatives are locked into the wood, they are perfectly safe for everyday use around your home.

WHERE CAN MCA PRESSURE TREATED WOOD BE USED?

You can use CULPEPER MICROPRO indoors or outdoors, anywhere durability and resistance to decay are important. Most building codes require the use of pressure treated or naturally resistant wood species in components that will come into contact with concrete, masonry, or exposed soil. Its decay resistance makes it ideal for subflooring in kitchens and bathrooms. It is also highly recommended for outdoor applications – for gardens and walkways, playgrounds and decks.

IS MCA PRESSURE TREATED WOOD SAFE FOR GARDENS?

Yes, CULPEPER MICROPRO is safe.  Scientific studies have proven that any copper that may migrate from the pressure treated wood becomes biologically inactive.  This causes no ecotoxic or other environmental impacts.  Culpeper Wood Products are safe to be used in raised gardens and will provide long-term protection.

Why shouldn’t treated wood be used for cutting boards or countertops?

The Food and Drug Administration discourages the use of any wood, treated or untreated, for cutting boards and countertops because these surfaces can become gouged during food preparation. Bacteria can grow in these gouges, creating unsanitary conditions in your kitchen. Only hard, abrasion-resistant materials should be used for cutting surfaces.

Do I need any special equipment to use treated Southern Pine?

No special equipment is required to work with CULPEPER treated lumber. However, always make sure to use the standard safety equipment for any woodworking project – gloves, air filters (to filter out airborne sawdust when cutting), and protective eyewear.

When building my deck what is the proper board spacing?

Wet after treatment deck boards should be installed by butting them tightly against each other. As the lumber dries, you can expect a 1/4" gap between the boards. When installing Culpeper KDAT (Kiln Dried After Treatment) boards you should leave a gap the width of an 8 penny nail (1/16”).

Click here to learn more on proper spacing for your deck boards.

Proper Board Spacing and Sealing End Cuts

Do I need to seal end cuts?

The answer is yes, we recommend you seal end cuts. CULPEPER pressure treated lumber has undergone a wood preservative treatment process to help it guard against a variety of insects, weather elements and even fire depending on the board type and manufacturer. When you trim boards to fit your project, don't forget to seal the end cuts by simply brushing or dipping the board in a bucket of copper Naphthenate wood sealant, or a product like Q8 Log Oil to ensure the newly cut board still maintains the exterior preservative treatment upon installation. For boards too large to dip or that are cut in place (like deck joists), apply the preservative with a paint or sponge brush to the cut end. The end cuts of a board are 250% more porous than the edges of the board, proper coating will reduce not help protect the wood against the elements, but improve the aesthetics of the finished product.

We suggest the following product which meets the requirements listed in the AWPA M-4 standard and Osmose warranty: Q8 Log Oil

How do I maintain the bright appearance of my deck?

No maintenance is needed to retain the treated wood's resistance to rot, fungal decay and termites.  However, a regular maintenance program will help maintain the appearance of your project. Wash your deck once a year to ensure a clean surface and seal it with an oil-based water repellant product with UV protection from a Culpeper Dealer.  This will also protect against splitting and checking.

Deck Maintenance: Staining & Sealing

WHAT CAUSES TREATED WOOD TO WARP?

Warping of southern yellow pine is a natural characteristic of both treated and untreated wood.  This is due to grain patterns that are established during the growth of the tree. No tree grows perfectly straight therefore grain patterns are irregular. Proper storage before, during and after construction will help minimize the amount of warping.

WHY IS MY WOOD SPLITTING OR CHECKING?

Splitting and checking are caused by the transfer of moisture between the wood and the surrounding environment. This constant wetting and drying of exposed surfaces causes stress on the wood that can create cracks and grain separation. Use of a water repellent will help reduce the natural tendency of wood to split and crack as it dries.  This does not affect the structural integrity of the wood.

Click here to learn more about maintaining your deck.

WHAT IS THAT INK STAMP AND HOW CAN I REMOVE IT?

Most sawmills mark their wood with an ink stamp which indicates the grade, species, sawmill, grading agency and other information. The grade stamp can be removed by lightly sanding with sandpaper or a palm sander.

Why can’t treated wood be burned?

Fire unlocks the bond between the preservative and the wood cells, leaving behind metal residues in the ash. This could result in an environmental or health hazard if not disposed of properly. It is recommended that sawdust and scraps of treated material be disposed of through normal trash collection services or by burial.