Don't Use Screws That Are TOO LONG or TOO SHORT! (Screw Length/How To Choose The Right Screw Length)

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Don't Use Screws That Are TOO LONG or TOO SHORT! (Screw Length/How To Choose The Right Screw Length)

People often ask how much screw they should use for fastening boards together. Screw length can be a tricky thing to figure out. This short video from The Honest Carpenter will show you a few rules of thumb that can help out in almost any situation.

The screws in this video fall int the "Utility Screw" category, and are "deck screws" in particular. This is a very good, common screw to use for strength in household projects.

#8 is the most common deck screw gauge. But, thicker #9 screws are showing up more frequently on the market as well these days.

If you're connecting two boards through the cross-grain, then you ideally want 1 to 1-1/2" of screw thread in the BOTTOM BOARD.

However, if the bottom board is thinner, like 3/4", then too much screw will punch through the back. In this case, size down to a 1-1/4".

When in doubt, used more fasteners! But be sure to provide them a little spacing--at least 3/4" apart.

When connecting into end grain, you need more screw length, because end grain doesn't hold screws very well. You ideally want 2" of screw thread in the bottom board. So, for 2x4 stock, you want to use a 3-1/2" screw.

However, if your stock is thinner here, like 3/4", then 2" of screw in the bottom board has a higher probability of breaking the wood, or bulging it. You may want to size down to a 2" screw overall.

RULE OF THUMB: In this application, you want 1/3 of the screw in the top board, and about 2/3 in the bottom board.

Thanks for watching!

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[villi_g]

I think that a lot of viewers would really appreciate it if the screw size-lenght-dimensions was in metric as well as imperial.

Keep up the good work!

[JustinMurrayfin]

Pre-drilling is often important to prevent splitting.

[HeHateMe]

1:15 "just add more screws"

So I gather you have run into my diy projects before

[onebylandtwoifbysearunifby]

Minor correction:
Screws hold *better* when they are pre-drilled with a pilot hole.
(Removing material for the core allows the threads to cut in a uniform fashion, avoiding distortion. This increases, not decreases, holding strength.)
-Good video👌

[yourstrulytonydollar]

As someone with a somewhat limited knowledge of woodworking and just getting into basic carpentry, your videos are a blessing to me. As a result, I'm taking on the challenge of replacing boards on my deck. Just wanted to say thanks and keep up the good work!

[Ensign_Cthulhu]

I like the one-thirds/two-thirds rule; it allows you to adapt your screw length to exactly the thickness of the materials you are working with.

[earlyriser]

this is an important topic for DIY where I don't know what screw size and length to use

[barrywhitlock]

Back in the day, wood screws were the only thing around. You would drill the diameter of the screw for the first board and then have a smaller pilot hole for the second board to cure withdrawal pressure. That still stands today for whatever screw is used today. If you think you are going to get pull out or withdrawal pressure, just drill the diameter of the screw for the first board. The head of screw will cinch up the 2 boards

[Cetok]

I've had instances where I needed to screw boards flat, but had screws that were slightly too long (I didn't order them). In that case, I just angle the screw slightly, making sure the boards don't slide and the screw doesn't exit. Simple but effective, especially if you put the next screw in from the reverse angle. Of course, don't be afraid to pre-drill the holes, especially if it's fragile work such as trim.

[chrisnash]

This is a great topic and you’re right about how many subjects can be covered regarding screws. I think what should be added in this conversation is what size hole to predrill.

Future suggested conversations...
Screw size needed for job
Course vs fine thread
Types of heads, (pan, flat, button, Phillips, Star etc.)
Exterior vs interior
Types of lag bolts
How tight to screw a lag bolt

Others have covered these topics, but you have a unique style that is short and to the point, yet adequate. You also carry enough energy and enthusiasm to keep people focused on your words.

[philarsenault]

Thanks Ethan. Didn’t realize end grain needed more length to stabilize the screw

[davidwooden]

An additional tip when drilling the pilot hole, use a bit that is roughly 1/3 to 1/2 the diameter of the threads. With lag screws or bolts go up to 3/4 of the diameter for the pilot hole to prevent splitinig.

[craiglee]

Hi Ethan. Just thinking of a few screw topics that you may want to discuss later. Two that come to mind are different drive options (#2 square / torx / phillips / etc??) and different coatings / materials (a lot of people use the wrong screw type - particularly in CCA treated timber). This video was fairly concise - that's good. A bit more depth in discussion around pilot holes such as when there may be advantage in drilling an over sized hole on the face piece to allow the stock to pull together without binding and when to counter sink may be worth while. Also scewing (angling) screws to improve holding power and fastening from each side where you have access.

[bunnydannels]

I really need a video on thread widths!
I’m so grateful for all your videos.

[edwardhappe]

This explanation makes a lot of sense. I had been taught that, in general, the screw length should be twice the thickness of the wood that one is attaching. i.e. a 3" nail through a 2x4. But I found myself making adjustments.

[richardstrada]

Great information. Now I won't "screw up" another project.

[SteveRogers]

I've also learned that lining screws up along the grain can split wood in half... I learned that the hard way. Always offset.

[normhodgkinson]

while installing water heater straps in a customers garage, i screwed through a 220 wiring that fed the kitchen oven opposite that wall. when i was holding one of the straps and touched the water heater, things became very exciting.

[PM]

For lateral pressure (like weight hanging from a fastener on a wall), you can improve performance by adding a vertical metal strip like a TV wall mounting bracket. Once the fastener grips the stud, the friction between the mounting bracket bracket and the dry wall also comes into play to support the hanging weight!

[RobbyStamenkov]

Please include metric units of measurement as well. Great video!