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Why Are My Decking Screws Snapping?

A well constructed and uniform looking deck is a great asset to any outside space. However, a botch-job deck with all the screws coming out, snapped off and unevenly spaced – will make your yard an eyesore. So how do we get those screws to stop snapping off and messing up the deck?

Wooden decking boards expand and contract as they get wet or dry, snapping often cheaply bought screws. To stop this, buy strong stainless steel or brass decking screws three inches long, and attach each board with at least two screws. Or invest in Trex composite deck boards that don’t warp.

Let’s dive down into this subject in more detail, considering exactly what type and size of screws to use and whether to pre-drill decking holes. We’ll also look at how many screws to use on different types of decking, and how to keep your lines of screws straight.

Why Are My Decking Screws Snapping? (Quick Answer)

Why Do My Deck Screws Keep Snapping?

The most likely cause of deck screws snapping is a combination of the boards and the screws. Simply, if the boards shift, it alters the pressure on the screws, and they may snap. We’ll be honest: this is more likely to occur with cheaper screws.

Why would the deck boards shift in the first place? They’re made from natural wood, so can dry out or take on moisture. This movement puts stress on the screws, which are now expected to hold wooden boards that are straining against them.

A good-quality screw will put up better resistance than a cheaper one. So, a good screw will hold and tight and hopefully survive a bit of warping, and a poor-quality screw will snap. You can also reduce movement (“cupping”) by using more screws in the first place.

How Do I Keep My Deck Screws Straight?

If you want a nice, neat line of deck screws, the best way to do this is mark out the joist line above the boards and work from this.

The best way to get a straight line, as any builder will tell you, is to use string. Start by laying your deck boards down, roughly where you need them to be, but without screwing them down. Make sure you can still see the top and bottom of each joist. Tap a nail into each end of the joists, then run a length of string between them.

You now have several rows of perfectly straight string that mirrors the line of your joists. You can either work round the string, or use it to draw a chalk line on the boards. 

Should You Predrill Deck Screws?

You do not have to predrill holes for your deck screws – but you really should. Drilling small holes reduces the risk of the boards splitting when you drill the final screw hole, as well as preventing strain on the screw itself (which is another cause of screws breaking).

The reason why we predrill deck screws is to prevent the deck from splintering. These gentle little holes put far less pressure on the wood. It also makes it easier for you when it comes to drilling the final holes (especially if you are drilling into hardwood)

Cutting this corner can prove a costly mistake, and we reckon even one split board is too many, as there’s really no excuse. Pilot holes aren’t hard to drill. You’re aiming for a small hole that’s about the size of the narrowest part of the screw. Use a slower drill speed for this part of the job.

What Are The Best Screws To Use For Decking? (Is it Brass?)

As decking is an outdoor application, most builders will immediately recommend stainless steel screws. They will survive damp conditions without corroding, and should be the go-to screw for any outdoor project like this. Solid brass screws are another rust-free option, and they certainly look nice against wood. However, they are not as strong as stainless steel.

Yes, stainless steel screws are more costly than other options, but they will last – and after all, you want your decking in place for a long time. A stainless steel screw won’t leak color into your decking boards; for example, some coated metal screws will eventually start to bleed their coating and cause a stain. If you live near the ocean, always go for super-tough marine grade stainless steel, which will withstand the salty and damp air.

This article is looking at how to fix screws into wooden decking. If you have a composite deck, you’ll need to buy specific composite screws. They’re easy to find, as they’re simply called “composite deck screws”. Never use normal wood screws on a composite deck as they will damage it.

How Long Should Deck Screws Be?

Most decking boards are somewhere between one and one and a half inches thick, and the screw needs to sink into the joists by at least an inch. So, the minimum screw length is two and a half inches. We’d suggest going up to three inch long deck screws, as these give you greater strength against those bowing and warping boards we mentioned earlier.

What about the screw’s gauge? Most deck screws have an 8 or 10 gauge diameter. For thread size, you’re looking for a pretty coarse thread (i.e., the threads are further apart). Any screw labelled suitable for wood should have the right kind of thread.

Don’t be tempted to use three inch nails instead of screws. They don’t have the right kind of tensile strength to manage the slight expansion and contraction of the wooden boards, and could end up popping out. 

Decking screws

How Many Screws Should I Put in Decking?

It’s a tricky balance: making sure your deck is secure, without it looking like it’s broken out in spots with screw heads everywhere. The general rule is to fasten each board with two screws at every point where the board goes over a joist. If it’s a rim joist, make it extra secure with three screws instead of two. This should give you a really tough and stable deck floor that will hold your yard furniture and cope with everyday foot traffic.

If this sounds like too many screws to you, and you’re worried about the finished aesthetic appearance of your decking, you can always use solid brass screws instead of stainless steel. These are also rust-proof, and have a lovely mellow shade that tones well with wood. Of course, if you have gone for a gray-toned wood, stainless steel actually works the best, aesthetically as well as practically. 

Do You Screw Deck Boards To Every Joist?

If you want a really tough deck, the best way to build it is to use two screws at the end of each board, then using two screws at the outside of the boards at every joist. So yes, we would recommend screwing the deck boards to every joist.

The advantage of this is that you have a really firm and stable deck, with plenty of screws holding the boards in place. This helps to prevent warping or cupping, as the boards simply don’t have as much room to move. Using longer screws also helps, as this will fix the boards firmly to the joists (three inch screws are perfect for this job).

But what if you have a lot of joists that are narrowly spaced together? Well, the good news is that you have a great foundation for your decking, but you may be a bit worried about the sheer amount of screws sticking up from the floor. Some people are not bothered about this – it’s part of the charm of a handbuilt wooden deck. However, others may want a more seamless look.

As we mentioned earlier, depending on the tone of your wood, brass or stainless steel screws can blend in well with the color of the boards. If you really don’t like the idea of screws being visible, an alternative is to choose a composite deck like Trex. You can get almost-invisible fasteners to attach your composite decking, so if you’re after a really smooth finish, this could be a better approach for you. 

Final Thoughts

Ultimately, your decking screws keep snapping because a) you bought cheap screws that are not up to the job, and b) your wooden decking itself is expanding and contracting as it gets wet and dry, then straining against those cheap screws.

The simple solution is to buy specialist thick stainless steel or brass decking screws – at least two and a half or three inches long – and attach each decking board with a minimum of two screws on every one.

If you don’t want your decking to warp and put stress on your screws at all – then you could invest in the more expensive option of Trex composite decking – which will save you a lot of hassle if you’ve got the budget.

Mark H.

Homeowner and property investor Mark H. aspires to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >