Most Versatile Exterior Screw
Eagle Claw Stainless Steel
TOP PICK: EAGLE CLAW
IN THIS GUIDE:
› WOOD DECKS: POWERPRO SCREWS
› STRUCTURAL: GRK RSS-185
› FURNITURE: XYLAN STAINLESS
› SHEET METAL: CASAON SCREWS
Intuition tells most woodworkers there is something special about using screws outdoors.
And you’re right.
While a stainless screw is generally the best outdoor wood screw, some cheaper (and more expensive) options won’t rust and degrade the look and structural integrity.
In this article, we’ll cover the following:
- Types of outdoor screws
- Outdoor screws for decks and furniture
- Screw coating and what works in various types of wood
- Painted projects
- Choosing screw length, thread style, and head designs
- Marine grade screws for water contact
Page Contents
Best Screws for Outdoor Use
From rain to snow to heat, one thing is guaranteed: outdoor structures take a beating.
And exterior screws hold most of these projects together as they expand and contract with the variations in heat and humidity.
So, maybe you’ve experienced a project that went bad with an improper screw.
Or, if it’s your first time, perhaps you want to avoid issues and start with the correct screw.
Either way – you are in the right place. And since screws vary from project to project and wood to wood, we’ll take a project-centric approach to show you options for screws.
Exterior Screws for Treated Lumber
Why consider screws by the type of wood?
Easy. Cost.
While most more significant projects, such as decks and porches, use pressure-treated lumber for their frames, it’s also economical to use treated lumber for the decking.
Types of Treated Lumber
One of the first things to know about treated lumber is that all treated lumber is different.
There are seven types of treated lumber, according to Front Range Lumber Co.:
- Borate for sill plate and, due to interior use, doesn’t require a particular fastener.
- PTI is the most common, new treatment for above-ground uses. Stainless steel or galvanized fasteners are recommended.
- KDAT is PTI-treated lumber that is “Kiln Dried After Treated” to remove moisture and provide for more excellent dimensional stability
- MCA is an enhanced PTI
- ACQ Exterior that requires stainless steel or hot dipped galvanized fasteners
- Non-Com for fire resistance
- CCA (Chromated Copper Arsenate) – not typically used.
Best Screws for Treated Wood
Available on Amazon: EAGLE CLAW or POWER PRO SCREWS
So what’s the most common treated lumber for DIY projects?
Either a variation of PTI or ACQ Exterior.
And both require Stainless Steel or Hot Dipped Galvanized Screws.
Recommended Screws (and Length)
The rule of thumb for most screw applications is the screw enters the second piece of wood to about half the thickness of the wood.
As an example, if you are attaching a 2×2″ wood baluster to a 2×4″ backer (1-1/2″ actual thickness), you’d opt for a 2-1/4″ screw.
But decking is different, as the joist is often 8-12″ in width (or more). And that is why you’ll commonly find decking screws at 2-1/2″ to 3″.
Recommendation:
- Decking: 3-inch Stainless Steel Screws
- Structural: Hot Dipped Galvanized Screws
- Budget: Some manufacturers will guarantee their screws for outdoor use for the life of the project like these Power Pro 48611 Screws that use a rust-resistant bronze coating.
Screws for Composite Decking
While composite decking is an excellent maintenance-free material, it’s also a material you’ll want to be thoughtful in selecting the right kind and color of the screw.
For example, if you’ve paid attention to composite decks, you’ve probably seen installations where screw heads “mushroom” the surface of the wood. As you might have guessed, it’s due to improper installation (no pre-drilling) or the wrong size screw.
Narrow Head Composite Screw
Available on Amazon: TrapEase Composite
Over fifteen years ago, I made several 12×12 cedar columns on my front porch and used TrapEase nails that blended perfectly with the cedar.
Fast forward to the summer of 2021, and a deck replacement with Trex and these TrapEase screws worked incredibly well. First, they have a smaller head that is harder to see than a standard screw. Second, with proper pre-drilling, they install easily with an impact drill. And lastly, they can be color matched to your deck.
Fascia Screws for Composite Decks
Available on Amazon: Trex Fascia Screws
While choice in color of decking with composite decks is great, as you can guess there is one problem.
Color matching your screws to the deck is vital.
Which makes fascia screws that can be pre-drilled and set flush with the face of the deck an important part of your exterior screw selection.
Choosing Outdoor Screws for Cedar or Redwood Projects
Without the chemical treatment found with treated lumber, the choices in screws for cedar and redwood are much broader.
However, using stainless screws in cedar is still the best option for the long-term durability of your project.
Types of Cedar
First, almost all cedar used for exterior projects is Western Red Cedar.
What is Western Red Cedar? Well, it’s a type of cedar that is:
- Found in the Pacific North West
- Is generally non-toxic and used in some medicines
- Old. As old-growth trees can be over 1000 years old
And due to its genetics, this type of cedar is built to withstand the exterior forces of nature.
What other types of cedar are there? Well, make sure you are aware not to use:
- Eastern Cedar – this cedar is toxic but is known for its aromatic smell and is not used for outdoor projects
- Exotic species from around the world
Redwood Characteristics
Like cedar, redwood will withstand the weather and resist cracking and warping.
But a few things to consider:
- Redwood has the same tannins as cedar that will corrode standard screws
- Stainless is preferred to avoid corrosion marking the surface of the wood
Redwood and Cedar Screws
The recommendations remain about the same as for treated wood, but a few options exist for matching the screw head to the wood color:
- Decking: Cedar Color Match Stainless Steel Screws
- Structural: Hot Dipped Galvanized Screws
- Power Pro: The budget Power Pro 48611 Screws features a rust-resistant bronze.
What Screws NOT to Use Outdoors
So you understand by now that stainless, hot-dipped galvanized, and silicon bronze are the best screws for outdoor wood.
And, for most jobs, even the lifetime warranty-coated screws are ok.
Screws not to use:
- Drywall screws
- Cold-dipped galvanized
- Interior grade trim or cabinet screws
- ..and any other screw not labeled for outdoor use
Screws for Composite Wood
After building and staining two cedar 15×18′ decks with a flight of stairs, I understand the desire for composite.
So what screws are best for composite wood?
Here are my recommendations:
- The torx-head CAMO Edge screws feature a head designed for composite installation and a solid torx head for non-slip installation.
Best Outdoor Screws for Marine and Boats
While stainless would be the best screw for marine use, one better screw is silicone bronze.
These screws have been around for decades and offer the best corrosion resistance in saltwater environments.
Would you be able to use it on a deck? No – you’ll pay too much. But these are great screws in your inventory for boat repair or water-contact projects. And they come in standard screw or bronze lag screw design.
Frequently Asked Questions
What screws are rust proof?
While coated screws offer a degree of rust protection, the best screws for rust prevention are silicon bronze.
How do you weatherproof a screw?
Any screw used outdoors must be designed and either coated or made for outdoor use. While indoor screws can be dabbed with silicone or other coatings, it doesn’t prevent the screw in the wood from absorbing moisture and failing.
Are deck screws waterproof?
Deck screws must be selected for their fit as an outdoor wood screw. Generally, this means a deck screw is either coated with a special sealant or made from high-grade stainless steel that will prevent rusting.
Summary
Hopefully, this article helped you decide on the best screws for outdoor projects.
While, as you’ve learned, stainless is more expensive, it’s a decision that will give you peace of mind that your project will last for years.
- About the Author
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Eric has been a professional woodworker for over thirty years and has worked in small cabinet shops making everything from kitchen cabinets to hand-made furniture. Now working from a home woodworking shop Eric is sharing his passion for woodworking, tool advice and how-to knowledge from his Minnesota-based woodshop.
I’m putting up a stockade fence temporarily till next Spring. I’m looking at screws maybe Hex so that they can be placed in and removed without real heavy damage. what should I use?
Hi Sharon – a structural screw like from GRK is usually best for outdoor in thicker lumber like a fence. The Torx heads are easy to install and remove. Consider installing them with the head facing the livestock or use bolts if they will be put to a lot of strain.