How Much Does it Cost to Seal or Waterproof a Deck?

Deck Sealing Cost Factors

How much you pay to seal your deck depends on the size of the deck, the level of prep work required, and the quality of both the sealant and the wood. 

Cleaning

Cleaning is usually bundled into the cost of the sealing job, but not always. Plus, the level of cleaning necessary to prepare the surface for staining determines the price. If you've got a fair amount of debris, you may need a power washing service. 

Power washing helps remove heavy dirt and stain buildup that standard pressure washing won't handle. Power or pressure washing a deck costs $250 to $400, on average. Be careful, though; too much pressure makes it easy to damage wood. 

Note that, while power and pressure washing use high-pressure water, a power washer also heats the water. If you use a power washer, be sure to keep the spray away from nearby plants and foliage. 

Alternatively, sandblasting costs $2 per square foot, or $40 to $65 per hour or around $860 total. It’s great for removing stubborn old stains and layers of old sealers and strips the top of any grease, dirt, or oil.

Labor

The majority of the costs involved in sealing a deck come from labor. The materials are comparatively inexpensive, but their application is time-consuming; there are no shortcuts if you want to achieve a good, lasting finish. 

The labor to seal and waterproof your deck costs $0.50 to $3 per square foot but can reach between $2.50 and $7 per square foot if you have multiple levels, spindles/balusters, stairs, and other features. With average labor costs of about $40 per hour, a 250-square-foot patio costs $125 to $750 in labor alone.

For some people, it’s worth hiring a professional to make sure it’s done right. Most of the price of the project comes from labor, which varies regionally. Also, expect hard-to-access projects, like two-story units, to take more time.

Size

Because pros price most jobs by the square foot, the size of your deck is important when establishing a budget. Smaller decks are more budget-friendly because they take less time to clean, prep, and seal.

Penetrant vs. Sealer

Penetrants soak into the wood’s surface while coatings sit on top of the wood. A coating sealer does both, whether it’s 10% coating with 90% penetrant or a full 100% coating. It's important to strip coatings before applying new sealers so that they can penetrate or coat the wooden surface effectively. 

However, with penetrants, you can seal over them, with the only preparation necessary a thorough cleaning. If you apply sealers in place of or in addition to stains, you can choose from a couple of types:

• Oil-based: A coating and penetrant. Harder to clean up and a little messier, but penetrates the wood and lasts longer.

• Water-based: Coating only. They clean up easily with soap and water, making them attractive to the DIYer, but less resistant to wear.

Sealant Prices

Most projects need two gallons of sealant which typically costs $50 to $80 total, but it can vary a little. Go for the best sealant that your budget allows. In general, the lower-priced options are the thinnest and least durable. Therefore, you'll have to have the deck resealed more frequently than if you chose a better-quality product to begin with. So, in this instance, going for the most affordable option is a false economy. 

Here are some of the more common brands that both contractors and consumers use:

• TWP (Total Wood protection): $30–$60 per gallon. Offers a full line of stains, cleaners, sealers, strippers, and brighteners.

• Behr: $35–$45 per gallon. A leading brand of stains, sealers, strippers, cleaners, and finishes.

• Thompson’s WaterSeal: $10–$40 per gallon. One of the most recognizable names in waterproofing and other exterior wood care.

• DEFY Wood Stain: $40–$55 per gallon. Offers a line of stains and cleaners designed for durability.

• Sherwin-Williams: $20–$50 per gallon. Durability claims have held up under numerous reviews, and one coat usually does it.

• Olympic: $15–$45 per gallon. Offers stains, cleaners, and resurfacers. There’s a product for every budget, making it popular with DIYers and contractors alike.

Cost to Seal and Stain a Deck

Applying both a sealer and stain together costs $700 to $1,000 total. You’ll pay $300 to $400 for the sealer and another $400 to $600 for the stain. You’ll see this often on two-tone projects. Sealing protects the wood from moisture, which can lead to mildew and mold buildup. Stains change a wood’s original color and provide a protective barrier, much like paint.

DIY Deck Sealing vs. Hiring a Pro

It’s worth it to seal or stain your deck, whether you do it yourself or have a pro come in. It’s an easy DIY project that just requires dedicating the time to do it properly. Many DIYers don’t do enough prep work, so the new seal fails early. 

The key is in the preparation. You'll need to rent a pressure or power washer if you don't already have one. Remember to be mindful of applying too much high-pressure water in a single spot for too long in one go, as you don't want to damage the wood; you just want to remove stains, debris, and old sealant layers.

If you don’t have the time, or need it to look professional the first time, find a local deck painting or staining service or hire a nearby handyperson who offers deck sealing services.

DIY Deck Sealing Costs 

DIY deck sealing costs are minimal, as you save on monetary labor costs. Instead, you'll pay for labor with your time and energy. The sealant usually costs between $50 and $80. If you don't have one, you'll need to rent a pressure washer which typically costs $50 per day. You can also purchase a pressure washer, with budget-friendly options starting at $100.

How to Seal a Deck

It's important to know how to seal a deck properly. The products you choose should have manufacturer's directions for use on the packaging. But there are some general steps you should take, whatever sealant you choose.

1. Sweep the deck clear of all loose debris

2. Clean the deck with a pressure washer or deck cleaning solution and hose

3. Leave around 48 hours for the deck to dry

4. Check for imperfections and residual stains

5. Spot clean troublesome areas or sand away the offending dirt or stains

6. Apply the sealant in thin coats, or as directed by the manufacturer

7. Leave plenty of time between coats for each one to dry out properly

FAQs

Should I clean my deck before sealing it?

You should absolutely clean your deck first. Cleaning before refinishing it is critical. If you don’t remove dirt and debris, you’ll be locking these moisture-trapping elements into your wood. This will keep any new sealer from doing its job and lead to failure and costly repairs. Whether you need to sand, power wash, or sandblast depends on its condition.

Is it better to seal or stain a deck?

Whether you seal or stain depends on many factors, including the type of wood, your climate, its age, and how damaged it is.

How much does it cost to power wash and seal a deck?

Power washing and sealing a deck costs $500 to $1,700, depending on size.

Do decks need to be sealed?

You don’t have to seal your deck, but if you want it to last, seal it with a waterproofer, paint, or stain.

How often do decks need to be sealed?

You should seal your deck every 1 to 3 years, depending on your climate.

Can I leave my deck untreated?

You can leave a deck untreated, but it’ll rot quickly, and you’ll replace it sooner rather than later. Deck replacement costs $4,000 to $11,500.

What is the best wood deck sealer?

It’s impossible to say which brand makes the best deck sealer. Most of them have similar formulations and pros vary on which ones they trust. Ask your professional to recommend one.

How much sealant do I need?

To work out how much sealant you need, work out the square footage of your deck by multiplying the length and width, remembering to account for stairs and railings in your calculations. This figure is the square footage required for each layer of sealant. For example, if your deck measures 8x10 feet, that's 80 square feet. So, each layer of sealant will be 80 feet of coverage. 

Next, check the product packaging for the total square foot coverage and how many layers the manufacturer recommends. For example, if the manufacturer recommends three layers of sealant for your 80-square-foot deck, you’d need 240 square feet of coverage from the sealant.