How to Hang Joists By Yourself

Now that I had my room cleared, the next step is to start building up the floor. Finally, the construction phase has begun! Joists are the main supporting structure of the floor. In my case, I had my exterior walls mounted to an existing slab foundation, but that foundation was 14″ below the rest of my house (hello 70s sunken living room!). Originally, my room was a garage, which was then converted to a funky sunken living room, now being converted to a level floor. I needed to frame in above that slab foundation to lay a new floor. Today’s post describes how to hang joists by yourself. The full vision for my project is here.

Rating (decode with the handy-dandy guide here):

• Time 
• Money 
• Tools  
• Experience  
• Strength 
• Risk 
• Suckage  

Tools:

• Measuring Tape
• Hammer
• Air Shim
• Level (2′, 4′, or string level)
• Speed Square
• Clamp
• Safety Glasses/Gloves

Step 1: Measure and Plan Your Room

Before you purchase your supplies, you’ll want an exact measurement of your room so you can formulate a plan. The easiest way to do this to measure the distance along each wall. It is important to measure ALL walls, even if they *should* be the same. Very few rooms are truly square, and older houses are notorious for being very out of square. A neat way to double check your measurements is to use your phone to capture room dimensions using the camera and built in sensors. My favorite app for this is MagicPlan. You can also use these dimensions inside of another cool app to help visualize the final result of your remodel.

Now that you know the exact measurements of your room, you need to figure out your joist placements. I whip out the graph paper for this, as it helps you accurately visualize your room.

Joist Orientation

Typically joists run across the short dimension of your room. For example, if your room is 10′ x 16′, you’ll have 10′ joists. However, in researching this article, I found MANY conflicting sources on how to orient your joists, so I won’t be offended if you opt for another way.

Joist Sizing

Now that you know how long your joists need to be, it’s time to size them. A general rule of thumb is take the distance of the span, divide by 2, and then add 2. This tells you the ACTUAL size the beam needs to be, not the nominal size.

For example, my joists span 11 feet. The above equation tells me my joists need to be an actual size of at least 7.5″. Now, the actual size of a 2 x 8 is actually 7 1/4″. Therefore, I need to size up from there, to a 2 x 10 (actual size 9 1/4″).

Joist Spacing

For floor joists, you want them placed “16 on center”, meaning from the center of each beam to the center of the next beam is 16″. You measure from center to center because of the differences in actual width of dimensional lumber. A 2″ x 10″ is not actually 2″ wide. Measuring from center ensures you have somewhere to place your sheet lumber, which come in 4′ x 8′ sheets.

The subfloor sheet lumber will be placed so that the short ends start and end on joists. The 16″ centers allows this to happen and ensures enough rigidity.

Putting It Together

Now that you have all your numbers, make your plan. You will need a “nailer” all the way around the room, so that you have something to set your subfloor on and something to nail your joist hangers into. Make your nailer out of the same dimension of joist (in my case, a 2″ x 10″).

From your nailer, space out your joists 16″ on center all the way across the room. Depending on your room dimension, you may have to cheat a beam over. For example, let’s say you run 16″ on center all the way across the room. The last span you have is 30″ on center. Instead of doing 16″ on center and ending up tight on one side, you can center that final beam so its more like 15″ on center.

If you look at my pictures you can see some strange joist spacing towards the doorway to the dining room. I did this because of existing hokiness I had to deal with. In a perfect world, your joists will all be 16″ on center. In reality, rooms are rarely easily divisible by 16″. Never make your spacing GREATER than 16″, and try not to make your spacing less than 8″ or you will have a hard time nailing in your joist hangers.

Step 2: Get Your Supplies

Now that you have a plan, it’s time to get your supplies. If you have a local hardware store, or other lumber source, I HIGHLY recommend using them to get your lumber. You will hate your life if you need to dig through the piles of junk dimensional lumber at the big box stores. I made the mistake of going to Lowes, and even with help it involved crawling deep into the racks and digging through probably 50 beams to get the dozen I needed. Keep in mind a standard size truck bed is only 8′ long, so your beams WILL stick out the back. A trailer would be the better option.

A Note About Nails

For each joist you will need two appropriately sized joist hangers (DON’T SKIMP HERE!!!). Now, here’s where it can get confusing. When you buy your joist hangers, right above the joist hangers will be nails labeled as “joist hanger nails”. You need some of these, but you need regular nails too! Look at your hanger and it should say what size nails you need.

For my joist hanger and my 2″ x 10″ joists, I needed 10D nails (also called 10 “penny” nails). 10D references the diameter of the nail. A standard 10D nail is 3″ long, while the joist hanger nails are much shorter, about 1.5″ long. The joist hanger nails will be labeled as 10D x 1.5″, or something like this. In the diagram above you can see these short nails will be used to mount part of the joist hanger, but you need standard 10D (or 12D, etc) to go through the beam and into the nailer behind it.

Get enough joist hangers, joist hanger nails, and standard nails to hang your joists. You’ll also need a way to mount your nailer to your studs, so don’t forget some 3″ deck screws (I like torx heads). This part might be different depending on the room you’re working in. In my case, my studs are mounted on top of the concrete foundation of the house. If you’re fixing a floor in an existing room, you probably already have a nailer there, so you might not need this part. Feel free to comment below and I can tell you what I’d recommend for your particular project!

Step 3: Mount Your Nailer

The nailer around the perimeter of your room will be the guide for the rest of the floor. Take the time now to ensure this is level with the rest of the room. If you have help, this can be accomplished by laying the level on the beam and adjusting until its level. If you’re working by yourself, this can be done with a string level. Just hammer a nail into the floor by the side of the room you want to be level, then run the string out to the far end with the string level attached. Mark on your stud where level is.

Now that you know where level is, cut your beam down to the correct size. Shim up one side of the beam until it is about where it needs to be, then go to the other end and use your 3″ deck screws to attach the beam to the joists flush with your level line. Don’t tighten the screw down all the way, it’s easier to mount the other end if you can rotate the beam slightly. Go back to the shimmed up side and drive a screw so the beam is level. Tighten up the screws on both end, and drive some into each stud along the beam.

Mount the rest of the nailers using the same method.

Step 4: Place a Joist

Now that you have your nailer in place, you’ve technically already mounted one joist. Use this first joist (the one butted right against the wall and running parallel to the direction you want your joists to go) as your guide and measure 16″ on center (or whatever your diagram shows if this end ends up off 16″ on center because of a funky room size). Mark on top of the nailer the center of where the joist needs to go. Measure and mark the opposite wall as well.

On the front face of the nailer (in my case, the 10″ side), use a speed square to draw a line perpendicular from the top of the beam and approximately the width of the beam apart. This line will be your guide when you mount your joists so they are perpendicular to the floor (ie not twisted, which significantly reduces their strength and will make mounting your subfloor a PITA).

Rough shim the far end of the beam so it is roughly the correct height (+/- 2″ works). On the near end of your beam, fit your joist hanger underneath the joist and flush with the end of the beam. Grab your clamp and hold it into place. Rough shim so this beam is close to level with your nailer. I found an AMAZING product called an Air Shim that I used to get the final shimming done to bring my joist level with the nailer. If you don’t want to spring the $20 for this product, you can use traditional shims, but you’re going to get frustrated with that pretty quickly.

Step 5: Nail in the Joist

Once your joist is level with your nailer and you’re happy with the location of the joist hanger on the joist, begin driving nails. Joist hangers come with little tabs that supposedly hold them in place while you drive nails, but the joists are WAY too heavy for that to work so I held the joist in place with the short nails. Don’t drive the long nails until you have both ends of the joist mounted and the joist level.

Go to the far end of the beam and use your air shim to get the beam the rest of the way level. Mount your joist hanger in the same manner. Now that the hangers are mounted and the joist level, go ahead and drive the long nails. I know this part sucks, but DON’T skip any nails. You risk compromising the strength of your floor if you do.

DO NOT USE SCREWS!!!!! THEY CAN’T HANDLE THE SHEER LOAD YOUR JOISTS ARE SUBJECTED TO!!!!

Repeat Steps 4 & 5

Repeat this until all your joists are hung, and voila! Your floor will start to look like a floor. This pic shows some of my joists mounted. I’m out of shape and didn’t feel up to hanging all the joists in one day, so I finished up the next day. Congratulations, you now know how to hang joists by yourself!

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