Best Screws for Outdoor Use

What are the best screws for outdoor use (and what NOT to use)

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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? Can I use galvanized (cheapest) or do I need to invest in stainless screws? Will all screws work with my types of wood? What works in treated? Composite?

Intuition tells most woodworkers there is something special about using screws outdoors.

And you’re right.

While the stainless screw  is the best all-around outdoor screw there’s a screw you likely haven’t heard of that is better.

Editors Choice – Most Versatile

Last update on 2020-07-14 at 20:10 / Affiliate links / Images from Amazon Product Advertising API

But we’ll get to that later.

Shopped for screws before? Then you know one thing: they are surprisingly EXPENSIVE. 

But, screws are a fraction of your lumber price so consider:

  • First, the wrong screw can corrode and stain your projects surface.
  • Then, if you don’t choose the right screw length, thread composition and head size you’ll impact the security of the structure
  • For water-contacting screws you’ll need a marine grade screw (eg. boats)
  • Lastly, you’ll be tempted on a decision between stainless and a coated screw  that offers up a lifetime warranty (but, who keeps the box?).

And, beyond being a cabinetmaker, I’ve built two 15×18′ decks, a massive cedar front porch, fences, two cedar playgrounds and garden fencing. So I’ve had to decide what screws were best for my outdoor projects.

Keep reading to learn what screw you’ll need by your type of project and wood. And, hopefully you learn a thing or two about wood and screws. Because I know I did while researching this article!
 
In a hurry? You can’t go wrong with stainless steel screws.

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

Screws for Pressure Treated Wood

Why consider screws by the type of wood?

Easy. Cost.

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

Stainless Steel 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″. 

Recommendation:

Choosing 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

Types of Cedar on Wood Deck

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

Redwood Characteristics

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:

  • Drywall screws
  • Cold-dipped galvanize
  • Interior grade trim or cabinet screws
  • ..and any other screw not labeled for outdoor use

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 Screws for Marine and Boats

Silicone Bronze Screws for Marine Use

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.

Good for a deck? No – you’ll pay too much. But for boat repair or water-contact projects these are a great screw to have in your inventory. And they come in standard screw  or bronze lag screw  design.

Summary

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.

Marine Grade (Boats)
Silicon Bronze Screws
Best DIY Projects
Stainless Steel Screws
Budget
Coated Steel
#8 x 1-1/2'' Silicon Bronze Wood Screws, Flat Head, Frearson Drive Qty 50
#10 x 3 Inch Stainless Steel Deck Screws 350 Pack 5 Pound T25 Star Drive Type 17 Point 18-8 (304) Grade Stainless Steel by Eagle Claw Tools and Fasteners
100 Qty #9 x 2-1/2" Inch Tan Fence & Deck Screws | Torx Star Drive | Bit Included (SNG919)
Coating
None
None
Corrosion resistant
Use in treated lumber?
Use in cedar/redwood?
Use in outdoor hardwoods?
Water contact?
Lengths
1/2″ to 3″ (usually shorter)
1″-5″
1″ – 4″
Marine Grade (Boats)
Silicon Bronze Screws
#8 x 1-1/2'' Silicon Bronze Wood Screws, Flat Head, Frearson Drive Qty 50
Coating
None
Use in treated lumber?
Use in cedar/redwood?
Use in outdoor hardwoods?
Water contact?
Lengths
1/2″ to 3″ (usually shorter)
Best DIY Projects
Stainless Steel Screws
#10 x 3 Inch Stainless Steel Deck Screws 350 Pack 5 Pound T25 Star Drive Type 17 Point 18-8 (304) Grade Stainless Steel by Eagle Claw Tools and Fasteners
Coating
None
Use in treated lumber?
Use in cedar/redwood?
Use in outdoor hardwoods?
Water contact?
Lengths
1″-5″
Budget
Coated Steel
100 Qty #9 x 2-1/2" Inch Tan Fence & Deck Screws | Torx Star Drive | Bit Included (SNG919)
Coating
Corrosion resistant
Use in treated lumber?
Use in cedar/redwood?
Use in outdoor hardwoods?
Water contact?
Lengths
1″ – 4″

Last update on 2020-07-14 at 20:21 / Affiliate links / Images from Amazon Product Advertising API

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