For outdoor building projects, many homeowners and professional builders rely on pressure-treated wood. The material is weather and decay resistant. Pressure-treated lumber is available in a wide variety of shapes, sizes, dimensions and lengths. When choosing fasteners to construct your pressure-treated wood project, certain types of screws are more desirable to use than others.
For fastening pressure treated framing, many builders rely on the strength and convenience of lag screws. These are large screws which may be as long as 18 inches. They have hex heads and are designed to be driven with a hand-held or power socket wrench. For use with pressure-treated wood, hot-dipped galvanised lag screws are highly resistant to rust. Galvanised screws are steel which has been coated with molten zinc when they are manufactured.
Vinyl Coated "Green" Screws
For attaching pressure-treated decking or stair treads, many builders use vinyl coated "green" screws. They are available in a wide variety of lengths and can be purchased at most home improvement retailers in 1-, 5- and 11.3kg. boxes. The vinyl coating prevents the screws from rusting. Most are outfitted with a tapered or trumpet head, enabling them to be driven into countersunk holes until the head of the screw is flush with the surface.
Composite Deck Screws
When installing composite planks, many builders use screws which have been specially designed and engineered for use with composite materials. The screws have two distinct thread patterns. The lower threads are designed to dig into the pressure-treated framing lumber. The upper portion of the shank is designed to penetrate composite decking without damaging the surface. These screws are also vinyl coated and are available in a number of colours to match the colour of composite decking.
Stainless Steel Screws
When constructing a deck, pergola, dock or other beachside structure using pressure-treated wood, the best type of screws are made of stainless steel. Not only will they securely hold decking and stair treads, they are extremely resistant to the effects of salt spray. They are generally more expensive to purchase than vinyl coated screws, but they are usually the fastener of choice for harsh marine environments.
Galvanised Deck Screws
Like hot-dipped galvanised lag screws, galvanised decking and framing screws are frequently used in pressure-treated wood construction. Like vinyl coated screws, they are available in a wide variety of lengths and shank diameters. Unlike galvanised lag screws which are driven with a wrench, galvanised deck screws have conventional slotted or Philips heads and are installed using a screwdriver or drill driver. They can usually be purchased from any merchant selling pressure-treated wood.