Can the Underside of a Deck be Painted or Stained?

When it comes to outdoor living spaces, I learned long ago that every detail matters, including the often-neglected undersides of elevated decks! Suppose you’re looking to refresh the appearance beneath an existing deck or add a finishing touch to a new one. In that case, you may be wondering about the viability of painting or staining underneath your deck—especially if you want to use the space as a bonus patio area.

Having worked closely with many homeowners, I’ve experienced firsthand how color can completely transform the underside of a deck to create an inviting outdoor space. Whether you prefer the natural warmth of wood stain or the crisp finish of paint, there are plenty of options for customizing this aspect of your deck.

Here, I’ll share information and my own tips for painting and staining the underside of your deck, including product selection, application techniques, and considerations for both new and existing decks.

Can You Paint or Stain the Underside of a Deck?

Yes, you can paint or stain the underside of your deck, from the backsides of your decking boards to substructure elements like beams, joists, and posts! Painting and staining are great options for enhancing the underdeck area, with the bonus of also providing those surfaces with an added barrier against moisture. The choice between the two depends largely on your desired aesthetic:

• Painting offers a versatile solution for concealing imperfections and achieving a uniform appearance. With a wide range of colors available, you can customize your underdeck however you like.
• Staining penetrates the wood’s surface, resulting in a natural look. Stains come in various opacity levels. Transparent and semi-transparent stains allow the wood’s natural beauty to shine through, while solid stains provide more coverage.

Whichever finish you choose, the possibilities are endless, and I’ve seen many fantastic results. You can match the decking finish overhead, choose a complementary shade, go for a bright or light color to add airiness and personality to your underdeck area, or even create a striped ceiling effect by finishing your joists in a contrasting color.

What is the Difference Between Paint and Stain?

Both paint and stain deliver color and protection and can be applied with brushes, rollers, or sprayers. But there are important differences, too.

Paint typically consists of pigments, binders, solvents, and additives. When applied to a surface, the pigments and binders form a solid film, providing a protective layer.

On the other hand, stains contain pigments and dyes dissolved or suspended in a solvent. When applied, the solvent penetrates the surface, carrying the pigments and dyes with it. As the solvent evaporates, it remains in the wood, enhancing its color and allowing the grain to shine through.

Comparison of Paint vs Stain

Choose the Right Finish for the Underside of Decks

I recommend exterior latex paint for your underdeck area for a uniform appearance that conceals imperfections. Paint forms a durable surface layer, but even when foot traffic isn’t a concern, there’s still a possibility of flaking or peeling over time—especially in moist environments. 

Choose a penetrating stain that enhances your wood’s grain and texture for a more natural look. The stain may gradually fade over time, but fading is less of a concern for the shaded underside of a deck where there’s little to no direct UV exposure, making it an attractive choice. 

To bolster either finish, I like to apply a matte sealer as the final step. Sealing is optional, but I like the added barrier against moisture, mildew, and other environmental factors that it provides. Sealer also enhances the color and appearance of finishes, and many homeowners I work with appreciate both the extra protection and the rich results.

Are There Any Differences for Painting and Staining Composite?

While we’re all familiar with painted and stained wood, you may be surprised to hear that composite decking may also benefit from a new finish. While the deck surface of some newer composites should not be painted or stained, you can generally still apply a finish to the underside. Check with your board manufacturer for specifics and use only finishes specially formulated for composites. For details on composite decking considerations, check out my article on how to paint your Trex decking.

Finishing the Undersides of Decks

I’ve found that if you want to paint or stain a new deck’s underside, pre-finishing before installation is the way to go. If you can avoid working above your head post-installation, you should. It just takes a little advanced planning. In addition to eliminating awkward overhead maneuvering, pre-finishing allows access to all surfaces, including the nooks and crannies that are more difficult to reach after installation. 

Speaking of planning ahead, if you want to keep the area below your new deck dry, you should also waterproof the deck. 

Finishing the underside of existing decks will involve overhead work, but don’t let that stop you! Apply stain or paint beneath your current deck by hand or using a sprayer.

A sprayer is a tempting option for quick and efficient application. However, I’ve seen instances where the paint or stain drifted up through the deck board gaps and settled on the surface above. Precautions, such as protecting the top decking surface with a tarp, are necessary to help mitigate overspray. 

If spraying is daunting, hand application of your paint or stain will be the best choice. While it requires more time and effort, brushing or rolling provides greater control over the application without worrying about affecting the decking surface above.

Underdeck Finishing Tips

• Surface Preparation: Clean, prepare, and allow the wood or composite to fully dry before applying your finish for optimal adhesion. Remove any peeling finish with a paint scraper if you’re refreshing an old paint or stain.
• Product Selection: Select an exterior-grade latex paint or oil-based stain for durability and weather resistance. Ensure that the finish is compatible with your surface, particularly for composites. Test a small area to preview the resulting shade when applying new stain over old.
• Multiple Coats: Evenly apply thin coats for the best finish and to avoid drips. Follow the manufacturer’s instructions regarding drying times in between. Use a roller for longboards and a brush for tighter spots. A rag may also be handy to wipe on stains in small areas.
• Optional Sealing: Once dry, consider applying a polyurethane exterior seal or varnish for added protection and richness.
• Patience: When pre-finishing components, let them dry completely before installation to avoid damaging the finish.

Remember, the underside of your deck is just as important as the top surface, so don’t overlook its enhancement potential. With some extra attention, you can transform the often-forgotten space under your deck and create an additional area that adds value and cohesion to your outdoor living environment.