When it comes to construction and DIY projects nails and screws are the two main fasteners. It can be difficult to decide which fastener to use. However, with a little research and knowledge the decision can be easy. Below I will help you decide if you should use a nail or a screw for your current project!
Nail vs Screw
Nail vs screw can be a tough decision. Screws have more fastening power to hold two objects together. Nails have more shear strength which allow some bend as a structure moves. This makes nails great for framing a house. Screws are removable, slower to install and more expensive.
Fastening power
When it comes to deciding between a nail and screw, this is the most important factor. Fastening power is how well can the nail or screw hold two objects together. After all the goal when using a nail or screw is to pin two objects together.
When it comes to fastening power there is really no competition, screws have significantly more strength. To understand this though lets take a look at the physics of each.
Nails
Nails rely on tension to create there fastening power. They are forced into a material (with a hammer or other tool) and then rely on the material to create tension around them. The nails tension is dependent on the material (the nail was forced into) to squeeze the nail on all sides.
Initially this tension is adequate for most jobs. However, as time goes on that tension will start to loosen. When this happens the nail starts to loose its fastening power.
Nails are smooth and flat, so they are unable to grip the material they are in. So as wood expands and shrinks (happens a lot with seasonal changes) the connection between the material and nail is lost. You can see this a lot if nails are used on a deck. Seasonal expansion and contraction will lead to nail heads sticking up. During winter you may actually be able to move the nails around because the wood contracts so much.
When the tension between the nail and the material is lost, the nail is basically useless. The nail is no longer holding the materials together. This can lead to serious issues especially if nails are used for load bearing objects.
Lastly, it is fairly easy to pull apart two boards held together by nails. Don’t believe me. Give it a shot. Try to pry apart two pieces of scrap wood that are nailed together. Initially they gave me a little trouble but once you jar the nail loose, the separate very easily. Below are the two boards I ripped apart using a screw driver.
Screws
Screws have much more fastening power due to the fact that they have THREADS. As screws enter a material they spin. This spinning of the threads allows small cuts to be made throughout the depth of the material. These small cuts and the threads act as anchors. These anchors prevent pullout from the material.
Try that same experiment we did with nails but use a screw this time. Fasten two pieces of wood together with a screw and try to separate them. It is nearly impossible to do. That’s because the threads grip the material so strongly.
So if your main goal for a project is to fasten two materials together, go with a screw!
Shear strength
Shear strength is another important factor to think about when choosing between nails and screws. Shear strength is defined as the materials ability to resist forces that can cause the internal structure of the material to slide against itself. Think of it as two objects trying to slide across one another.
In short nails have much more shear strength then screws. Nails are more flexible in the lateral direction (which is necessary for shear strength). Nails will bend but not break when it comes to lateral forces.
Screws have minimal to no strength in this lateral direction. They will snap very easily if any shear forces are applied to them.
You might be asking yourself what are some projects that undergo a lot of shear strength? Well surprisingly enough, houses and structures can be prone to lots of shear forces. Lots of wind, earthquakes, or hurricanes will put a lot of shear force on standing structures. That is why in most areas code requires you to use properly length nails when framing.
The high shear strength of nails will allow the nail to bend/flex with the movement of the frame without snapping. The nail will bend as the structure shifts. Also since framing is internal it is not exposed to big temperature shifts. This will prevent nails decreased fastening power to be an issue. However, often times contractors will use nails in combo with fastening glue to help strengthen the bond. The nails act as a temporary adhesive as the glue dries. Once the glue dries the bond is very strong between the materials (almost as strong as screws).
Type of project: permanent vs temporary
Permanent vs temporary job is very important to consider when deciding between nail or screw. This one is quick and easy, nails are permanent and screws can be temporary. So if the project is permanent you can use nails. If the project is temporary definitely use screws. There are other factors to consider when deciding but that’s the basics.
Prior to any home project, always ask yourself: am I going to want to take this apart later? If the answer is yes, go with screws!
Above you can see nails are used for baseboards which for the most part are permanent. While screws are used for door hinges. Sometimes doors and or hinges have to be removed.
Screws are very easy to take out of material. They will back right out when using a driver/drill. This keeps things very clean and easy. All you are left with once the screw is removed is a small hole.
Nails on the other hand are extremely difficult to remove once they are hammered all the way down. When trying to remove a nail you will likely destroy the material and nail at the same time. You will have to use other tools to do this and it will make for a very sloppy/messy project.
Price
In general screws tend to be much more expensive then nails. Screws are harder to make (because of the threads and heads), therefore the price will be much higher. This is an important factor to think about. Will your project require a lot of fasteners to be used? If so to keep the price down it may be best to go with nails if able.
As you can see above the cost for 25 lbs of nails is $58.76. While the cost of 25 lbs of screws is $119.0.
Speed of install
Another factor to keep in mind is the speed at which you can install each fastener. Nails are by far much faster to install then screws. You can often do 5-10 nails by hand to every one screw. If you are using a nail gun then you can do up to 20 nails for every screw. Brad and framing nailers can really increase your speed.
Most of the time screws need prep work before you can even insert the fastener. Trying to insert a screw into a material without prep can be very difficult. That’s why screws often require pre-drilled holes to be made with a bit.
Nails do not require any prep work at all. You can just drive a nail into the material without a pre made hole. This makes the speed of install for nails significantly faster then screws.
Conclusion
There are a couple of different factors that go into choosing between nails vs screws. The two most important factors are by far fastening power and shear strength. Those should drive the initial decision. Then after that you can factor in things like cost, speed and temporary vs permanent project.
- Fastening power
- Nails
- Screws
- Shear strength
- Type of project: Temporary vs Permanent
- Price
- Speed of install
I hope this answered all of your questions in regards to fastener selection: screws vs nails. If so please let me know in the comments!
A current home owner and dad of two, who loves to fix things. I have spent countless hours fixing and repairing things around the house. I started this blog to share my knowledge with you. I hope you find what you are looking for!