Seal-Once Marine Waterproofing Wood Sealer

Made by U-C Coatings


Seal-Once Eco-Friendly Marine Waterproofer for Wood is a green stain/sealer product formulated for exterior use on properly prepared, unsealed wood surfaces. Seal-Once Marine is a high-performance, toxin-free, water-based waterproofer and wood sealer that provides long-lasting protection to all wood surfaces.

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Seal-Once™ Marine Waterproofing Wood Sealer is the environmentally friendly choice for long-lasting wood protection. If your wood is properly prepared and ready for sealing, use Seal-Once Marine to waterproof, protect and seal your wood for up to 6 years. And, because Seal-Once Marine is non-toxic, and has no VOCs, it is quickly become the leading brand in eco-conscious construction and home care.

Try Seal-Once Marine today and learn why it is endorsed by leading environmental organizations like the  N.H. DES and is GreenSpec™ Listed.

Learn More About Seal-Once Marine

Product Type: Water-based formula

  • Non-toxic, zero VOC’S, safe for the environment
  • Safe for use over fresh or saltwater
  • Will not harm fish, plants or pets, livestock or people
  • Water-based, odorless, non-flammable, non-combustible, will not burn skin
  • Paintable, stainable, breathable
  • Long-lasting, deep penetrating bond
  • Outperforms all other sealers & stain
  • UV stable
  • Waterproofs, reduces mold and mildew
  • Protects against cracking, splitting and warping
  • Clear formula allows wood to turn gray naturally
  • Semi-transparent tints add color without hiding wood grain
  • Non film forming
  • Easy soap & water clean up
  • Made in the USA
  • Veteran-Owned
  • Approved for use by NH DES and is Green Spec Listed

seal once marine example on deck over lake

Minimum 6 Year Warranty

Seal-Once Marine is so carefully crafted, that the manufacturer is offering a 6 year warranty on all horizontal surfaces like decks and docks, and a 10 year warranty on vertical surfaces like siding and railing support. The manufacturer will refund you the complete purchase price of the product is it does not last, so take advantage of this guaranteed deal today.

Use Seal-Once Marine on all your wood surfaces:

  • Docks
  • Piers
  • Decks
  • Railings
  • Retaining Walls
  • Fences
  • Planters
  • Outdoor Furniture
  • Boardwalks

Cutting Edge Nano-Tech

Seal-Once Marine’s proprietary nano-technology protects your wood at the sub-micron level. Each molecule joins together to produce a lattice framework, connecting deep into your wood’s fibers, forming a long-lasting bond that protects and seals your wood, keeping it safe from UV rays and corrosive sea water. When Seal-Once Marine cures, it creates a dense but transparent film, preventing moisture from coming in contact with the wood.

The Green Choice

This non-toxic waterproofing wood sealer can be used on decks and docks, even over open water, as it exceeds current eco-requirements. It will not harm plants, pets, livestock or people, is non-flammable and non-combustible. It will not burn your skin, and is so easy to clean up, you can just use soap & water. If you are serious about protecting the environment and your wood, try Seal-Once Marine today.

Seal Once Marine Protects your wood from:

  • UV rays
  • Mold
  • Mildew
  • Water
  • Cracking
  • Splitting
  • Warping


The unique water-based formula of Seal-Once Marine outperforms all other sealers and stains on the market. Get Seal-Once Marine today in a clear finish or one of these semi-transparent tints:

Seal-Once Nano plus Poly clear color

Seal-Once Nano plus Poly Light brown color
Light Brown

Seal-Once Nano plus Poly Natural color

Seal-Once Nano plus Poly brown color

Seal-Once Nano plus Poly Dark Mahogany color

Seal-Once Nano plus Poly Deep Redwood color

Seal-Once Nano plus Poly Bronze Cedar color
Bronze Cedar

Seal-Once Nano plus Poly cedar color

Seal-Once Nano plus Poly Black color

Seal-Once Nano plus Poly Coastal Gray color
Coastal Grey


Note: Tints are shown on Red Cedar. The clear finish (not Natural) will not have UV protection, but will have the same great waterproofing and warranty.


Coverage varies based on how porous your wood is. At least two coats are required. Do not thin Seal-Once Marine.

1 Gallon 200 – 300 square feet, per coat
5 Gallon 1000 – 1500 square feet, per coat


 Seal Once Marine Waterproofing Wood Sealer


Learn how to apply Seal-Once Marine.


When to Apply

You know it’s time to waterproof your wood when:

  • After rain the water is soaking into the wood instead of running off.
  • Your wood is warping, cracking or splitting.
  • Your pressure treated wood is at least 6 months old.
  • Your wood has been cleaned and is completely dry (We recommend All Wood Cleaner for proper deep cleaning).
  • There is no other waterproofing product on the wood.
  • The air temperature is above 35 °F (2 °C).

If your wood has deep stains or mold, we recommend pressure washing with a wood cleaner and brightener before you apply Seal-Once Marine.


Mixing in The Tint

Seal-Once Marine in Natural, Bronze Cedar, & Coastal Gray tints comes premixed in the container. All other tints come in a separate bottle, and you combine them when ready to use.

When you receive your Seal-Once Marine, it will come as a clear base. If you ordered a tint, it will come in a small bottle. Each tint bottle is enough tint for 1 gallon of clear base.

  • If you have a 1 gallon of clear base, mix in 1 bottle of tint.
  • If you have a 5 gallon of clear base, mix in 5 bottles of tint.

Mix or shake thoroughly before you begin, and frequently throughout the application. This ensures a uniform color.


Applying Seal-Once Marine

Tools: You can use a bristle brush, air assisted or airless sprayer (use tip size between 0.017″ – 0.019″)

If possible, apply Seal-Once Marine in the shade for the best results. If applying in the sun is unavoidable, lightly mist the wood, and immediately apply Seal-Once Marine. Do not apply if it is going to rain that day.

  1. Apply at least two coats of Seal-Once Marine. Keep applying the first coat until the wood will not absorb anymore.
  2. Start the second coat as soon as the first is damp, but not wet. Older wood will need more applications
  3. Keep applying coats until all holes and cracks have been filled.
  4. If using a sprayer, apply Seal-Once Marine in a medium or coarse spray pattern, and use a bristle brush to remove any puddles.
  5. Cover the entire surface and ends of the wood.

Seal Once Marine Waterproofing Wood Sealer

Dry Time for Seal-Once Marine

  • The temperature and sun exposure affect drying time. Expect Seal-Once Marine to be dry enough to walk on in 2-3 hours.
  • After 24 hours, you can apply paint or stain.


How to Clean Up Seal-Once Marine

Clean up is simple with Seal-One Marine. Clean all equipment and brushes with warm water and soap. Seal up any remaining Seal-Once Marine, and store in a place that will not freeze. Seal-Once Marine has an indefinite shelf life.



  • While Seal-Once Marine will not harm plants or animals, it is a minor irritant if you get it in your eyes, inhale it or swallow it.
  • If you get Seal-Once Marine in your eyes: Rinse thoroughly with clean water for 15 minutes.
  • If you inhale Seal-Once Marine: Move to fresh air.
  • If you get Seal-Once Marine on your skin: Wash thoroughly with soap and warm water
  • If you swallow Seal-Once Marine: Drink 2 full glasses of water and contact medical personnel. Do not induce vomiting.

A Warning About Lead

Seal-Once Marine is safe to work with, but lead is not. If you are sanding or removing lead, visit or call 1-800 424-LEAD before you begin your project to find out the safest way to remove it.


Ongoing Maintenance of Wood with Seal-Once Marine

Portland ME Dock Photo Portland ME Dock Photo Portland ME Dock PhotoPortland ME Dock Photo

A dock in Portland, ME that was treated seven years ago with Seal-Once Marine Cape Cod Gray, and has just been retreated.

You know it’s time to reapply Seal-Once Marine when:

  • Water on the wood soaking into the wood fibers instead of running off.
  • Color (tint) is fading.
  • There is surface damage that exposes bare wood.
  • High traffic areas have worn away Seal-Once Marine
  • Any time the wood looks noticeably different.

You can apply Seal-Once Marine as often as you’d like. But before you do, you must clean the wood to ensure the next coat will penetrate into the wood, as well as remove mold, mildew, stains, and grime. Do not use corrosives, oxidizers, or any strippers to clean your wood. We recommended using only the following cleaning solution:

  1. 1 gallon of warm water
  2. 14 ounces of household bleach
  3. 1 ounce of Dawn® Dish Detergent

Apply your cleaning solution with a sprayer and allow the solution to rest on the wood for 20-30 minutes. Then, thoroughly rinse of the wood with a garden hose.

Once your surface is clean and dry, reapply Seal-Once Marine following the Application instructions above. If apply Seal-Once Marine to only a small area, make sure to slightly overlap the new coat with the old, to ensure a uniform look.



New Image Coatings, LLC Performance Guarantee:

LIMITED LIABILITY: Liability, whether expressed or implied, is limited to replacement of product or refund of purchase price if this product [Seal-Once™] fails to prevent ingress of moisture for six (6) years horizontal and ten (10) years vertical surfaces when used according to label instructions.

New Image Coatings Cleaners performance warranty and liability, whether expressed or implied, is limited to replacement of product or refund of purchase price if the cleaner product fails perform as promised when used according to label instructions.

Liability cannot include labor costs or consequential damages. Liability cannot be modified or extended by manufacturer’s representatives, distributors, or dealers of New Image Coatings, LLC products.


About Waterproofing Pressure Treated Wood

When should I apply Seal-Once Marine to new Pressure-Treated Lumber?

There is some disagreement about when to apply a waterproofer to pressure-treated wood.
Pressure-treated lumber is treated with chemicals during the manufacturing process, to prolong its life and reduce maintenance. In addition, pressure-treated wood is well, “pressure treated”, which causes it to become more dense than regular wood. These two modifications to the wood means it is not ready for any waterproofing for some time, and there are several other factors that affect the wood as well.

The short answer is, do a water test: spill a small amount of water on the wood. If it runs off right away, keep waiting. But if the water absorbs into the wood or puddles up, it’s time to add a waterproofer.



MSDSClick here for this product’s Safety Data Sheets (SDS)


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