If you haven’t built an outdoor structure before a common question is a basic, but great one: what are the best screws for outdoor use? While your project won’t have immediate issues, choosing a screw that wasn’t designed for water and the elements will eventually cause damage. In this article learn what types of screws work best outdoors.
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 there are some cheaper (and more expensive) options.
In this article we’ll cover:
- 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
Personally, I try to keep the screw cost in context of the project and overall cost. While there is always a premium screw, it doesn’t make sense if it’s features won’t matter in 5 years.
Lastly, if you haven’t converted to using a hammer drill for driving screws you are missing out. A hammer drill with longer screws in outdoor application will not only drive faster, but reduce screw head stripping.
Top Outdoor Screws
Best for wood decks:
› PowerPro 3-inch Screws at Amazon ($13.99)
› Eagle Claw 1-5/8 Inch at Amazon ($15.95)
› GRK RSS-185 at Amazon ($23.89)
Best for outdoor furniture:
› Bolt Dropper Xylan S/S at Amazon ($13.99)
Best Screws for Outdoor Use
From rain to snow to heat one thing is guaranteed: outdoor structures take a beating.
And, exterior screws are what holds 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’s went bad with the improper screw.
Or, if it’s your first time, perhaps you want to avoid issues and start off with the right 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 showing you options for screws.
Exterior Screws for Treated Lumber
Why consider screws by the type of wood?
While most larger projects, such as decks and porches, use pressure treated lumber for their frames it’s an economical decision to use treated lumber for the decking as well.
Types of Treated Lumber
One of the first things to know for treated lumber is that all treated lumber isn’t the same.
In fact, 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 special 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 greater 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
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 balusters 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″.
Screws for Composite Decking
While composite decking is a great maintenance free material, it’s also a material you’ll want to be thoughtful in selecting the right kind and color of 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
Over fifteen years ago I made a number of 12×12 cedar columns on my front porch and used TrapEase nails that blended in 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 small head that is harder to see versus a normal 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
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 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 in old growth trees can be over 1000 years old
And, due to it’s genetics this type of cedar is built to withstand exterior forces of nature.
What other types of cedar are there? Well, make sure you are aware to not use:
- Eastern Cedar – this cedar is toxic, but is known for it’s aromatic smell and is not used for outdoor projects
- Exotic species from around the world
Similar to cedar, redwood will withstand the weather and resist cracking and warping.
But a few things to consider:
- Redwood has the same tannin’s 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:
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.
But what shouldn’t you use? Well, don’t even consider:
Screws for Composite Wood
After build 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 strong torx head for non-slip installation.
Best Outdoor Screws for Marine and Boats
While you’d think stainless would be the best screw for marine use, there is one screw that is better: silicone bronze.
These screws have been around for decades and offer the best corrosion resistance in even saltwater environments.
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 is made from a high grade stainless steel that will prevent it from rusting.
Hopefully this article helped you decided what are the best screws for outdoor use on your projects.
While stainless, as you’ve learned, is more expensive it’s a decision that will give you piece of mind on what you make for yourself.
Or for others.
- 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.