Decking Screws, which ones should I use explained here…
Stainless, coated or does it really matter? Of course, it does…
Stainless Steel Decking Screws
Stainless is by far the best for exterior use, either A2 or A4 stainless
The A2 stainless steel grade screw or fixing has a good corrosion resistance under standard construction use in environments that are wet, oxidising and where organic acids or alkali and salt solutions are present. The A4, however, is sometimes called “acid proof” steel grade, as it is has an enhanced corrosion resistant than the A2. The A4 proves to be resistant in highly corrosive environments such as sea climates and use areas with lots of oxidising acids.
A4 bolts are more corrosion-resistant because of higher chromium content. The negative attribute of a higher content of this element is that it makes the fixing more fragile and under high torque, applications may be susceptible to crack. Because of this, the A2-fixing, which is already very resistant against corrosion, has a more popular use than the A4.
Although A2 and A4 are both classified as stainless steel fixings, A4 includes 2 to 3% of the element molybdenum. This provides extra resistance to chloride corrosion and reduces metallic contamination, making it suitable steel for surface finishing where aesthetics is required.
A good indicator of a good quality coated decking screw is to look for Salt spray testing and Kesternich testing. For instance, GRK fixings that have the Climatek™ coating have exceeded “1,200 hours and 30 Kesternich cycles.”
Do note that whilst some fixings are approved for use in ACQ, Copper Azole, Cedar, and Redwood applications, they will not be warrantied if close to salt water or if you use de-icing salts in the winter.
Does it really matter?
I would have to ask how long you wanted the installation to last first of all and then see what screws you propose. Assuming a short life expectancy then any screws will do and for a long life deck I would always recommend A2 stainless and for marine or enhanced salt water environments A4.
Do consider the aesthetics of the screw head finish prior to your screw selection.
Pozi, Trim-Head, Torx, Square Drive…Your choice
What decking screws are available?
There are many more…
What Screws should I use?
For hardwood I would use a broad shouldered screw or one with a bugle head; if you are considering a trim head screw with hardwood – I would reconsider as they will not provide a secure fixing for the thicker decking boards.
For composite deck fixing I would recommend whatever is suggested by the manufacturer; for two reasons, one – the manufacturer has tried and tested so in most cases is suggesting the best screw for their product. Two- you lose the warranty if you use a fixing that is not approved.
Screws for side fixed decking; again here I would go with the manufactures recommendation.
More on deck board fixings.