5 Tips for Using Medium Density Fiberboard Outside

stack of fiberboard panels
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Particle board or composite describes a broad class of building materials. While particle board as a whole isn't as durable as traditional wood, it is versatile enough to have merit and uses. Medium density fiberboard (MDF) is one of the popular types of composite board.

If you're going to be working with MDF, you'll need to understand its limits as well as its construction.

Particle boards are created by mixing together a slurry of wood chips, saw dust, and adhesive resins. The mix is shaped into boards and baked at high temperatures and pressures. The chips and glue harden into a sheet that can be cut, drilled, nailed, screwed, and stapled.

1. Understand its Limits and Uses

Medium density fiberboard is easy to work with because it is made with fine particles. When cut, these particles leave smooth edges rather than rough ones that are common of many other types of composite.

Medium density fiberboard has many common applications. It is used for furniture, shelving, laminate flooring, decorative molding, and doors. It is also used in vehicles, where it is formed into dashboards, shelves, and door shells.

You may notice all of the applications of MDF are either as indoor components or pieces that are otherwise shielded from heavy exposure to the elements. It can not last in harsh conditions and should never be used for external framing and construction. Stick to heavy-duty lumbers such as plywood and OSB for these uses.

That's not to say it can't be used outdoors. It just isn't as durable in certain outdoor applications, so builders tend to use alternatives.

2. Have Realistic Expectations

black mdf shelving

Choose a project that is appropriate for medium density fiberboard. Building a bench, chair, or shelving unit is a suitable application. Building a shed or roof is not.

Construct a piece that is practical for outdoor use but small enough to drag under shelter when the weather turns bad. If you have a major construction project in mind, use a different material for it.

3. Choose Veneered Fiberboard

Fiberboard has a muted appearance. With veneered fiberboard, the top layer is usually coated with a thin veneer of some other wood, such as mahogany, oak, or even pine. This veneer improves both the aesthetic and structural properties of the fiberboard. Choose a strong finish to resist water and dirt that the piece will inevitably encounter outside.

If you cut the edges, you will expose the fiberboard’s core. The core does not have the same veneered finish as the top. If any unsightly or glaring instances of the core are exposed, add a new veneer piece to the sides if necessary.

4. Choose Moisture Resistant Fiberboard

stack of mdf pieces

Most fiberboards are made with urea-formaldehyde glue. This type of glue is cheap and is one of the things that makes MDF so affordable. Unfortunately, the same resin offers limited moisture resistance.

Try to find medium density fiberboard manufactured with phenol-formaldehyde glue. This fiberboard is more rare because the glue is more expensive. The quality of that glue is reflected in the price you'll pay, but the moisture-resistant properties will make it worth the investment.

5. Waterproof Your Piece

As you build your piece, assemble it so the unfinished surfaces face inside or remain on the bottom. You specifically paid for a fiberboard with veneered surfaces, so make sure it 's facing out.

For extra protection, paint the piece with waterproof sealant. If you use waterborne polyurethane, it may not bind readily to the surface of the medium density fiberboard. Try sealing the board with shellac first, then coating it with polyurethane.