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What Are Deck Screws?

A man using deck screws to secure the boards of a deck.
Various nuts, bolts and screws.
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  • Written By: S. Mithra
  • Edited By: Lindsay D.
  • Last Modified Date: 28 July 2014
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Since wood decks have many thin planks and must withstand harsh environmental conditions, deck screws are designed to accommodate the challenges of this application. They must resist corrosion, drive easily, and lay smoothly against the deck surface, called countersinking. For these reasons, many deck screws are self-countersinking, self-drilling, and coated with materials that won't rust.

Like other screws, deck screws come in a wide variety of lengths and widths, called shanks. They also use different shapes of driver, the part on the screw head that allows a screwdriver to dig in to the wood and rotate. A popular head shape is a square, because it holds the driver and doesn't strip as easily as Phillips heads.

One feature of deck screws that makes them easy to install is the sharpness of their point. They often come to a very sharp, narrow point, to reduce the necessity of drilling pilot holes. Especially in a soft deck wood like cedar, these screws can be fastened without needing to pre-drill the hole, called self-tapping.

Secondly, screws designed for a deck will propel themselves into place because of their unique shank design. The thread of the screw is measured in degrees, so a shallower degree means more thread along the length. These threads spread out the force, so the screw takes less effort to put in, yet it is still difficult to pull out. Some types of deck screws are lubricated so they slide into the wood even more easily.

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The most important characteristic of deck screws is their resistance to corrosion. This is determined by the type of metal or metal coating that doesn't succumb to rust. For example, zinc plated (galvanized), stainless steel, high copper content, and ceramic-coated screws are appropriate for exterior use on decks or fences because they won't stain the timber.

Recently, composite decks made out of specially developed materials or pressure-treated wood have become popular. Since these deck planks are not standard lumber, special deck screws had to be designed to work with this material. Regular, self-countersinking screws caused the plank to "mushroom," meaning that the material pulls up in a hump around the screw head. Make sure to use the screws that the composite deck manufacturers recommend to avoid such issues.

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anon314827
Post 7

@rpilkey: Don't know when you posted this, but I would replace all the screws in horizontal places (decking) right away before they start to rust and cease in the wood. It's easy to do. Unscrew the old and match the size with the new. Then it's up to you if and when you want to replace all the screws in the vertical pieces (railings).

In other words, if water can "sit" on the screw, replace it right away. But also remember that wood absorbs water. Even though the screws in the vertical won't rust as fast as in the horizontal; they will rust from the moisture in the wood.

rpilkey
Post 6

So the handyman we hired used screws that are "not recommended for ACQ" for some ACQ pressure-treated steps+railing. Does this mean the screws should be replaced? Every reference says they will rust more quickly, but how quick is "quicker"? 1 year? 10 years instead of 20? This is in Ottawa, Canada, if the weather matters. Roger

anon107258
Post 5

I'm assuming you've already tried using a power drill and the correctly sized square-drive driver (perhaps trying it first on your drill's low power setting), and reversing them out? --Bill

anon104462
Post 4

Get a tool called a "Grabit" (not sure on spelling). Best tool in the toolbox, speaking from a frustration standpoint. Put yourself in the position of a stripped screw and you'll be saying the same thing! Easy to use, only about $10 or so!

FirstViolin
Post 3

A good tip for figuring out which deck screw size you need is to make sure that when you tighten the screw down, you still have at least an inch of thread down into the receiving board.

That way you can make sure you have a good strong connection.

Of course this is not a hard and fast rule, and you should consult a contractor when building a deck for the first time, but it's just a little tip to keep in mind.

gregg1956
Post 2

Been there and done that. Your best bet is to go to a hardware store and get a screw extractor bit.

That way you don't have to worry about stripping them.

Just explain it to the store employees and they'll be able to set you right up.

TunaLine
Post 1

Does anybody know how to get deck screws out of the boards afterwards?

I'm trying to replace the deck on my house, and getting those guys out is turning out to be a huge pain.

They're square-headed, and stainless, if that gives you any better idea about what I'm dealing with.

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