Materials:

• Subfloor Panels: Typically, plywood or oriented strand board (OSB) in thicknesses of 3/4-inch or 5/8-inch.
• Joists: Wood framing where the subfloor is attached. Typically spaced 16 inches or 24 inches apart.

Fasteners:

Screws:

• Type: Use subfloor screws or deck screws designed for wood-to-wood applications, as they provide better holding power than nails and help prevent floor squeaks.
• Size:
  • For 3/4-inch thick subfloor: Use screws that are 2 1/2 inches to 3 inches in length.
  • For 5/8-inch thick subfloor: Use screws that are 2 inches to 2 1/2 inches in length.
• Material: Coated screws, typically galvanized or zinc-plated to resist rust and corrosion.
• Drive: Phillips or square drive heads to prevent stripping during installation.

Nails:

• Type: Use ring-shank nails or spiral-shank nails, which have extra holding power compared to smooth nails.
• Size:
  • For 3/4-inch thick subfloor: Use nails that are 8d (2 1/2 inches).
  • For 5/8-inch thick subfloor: Use nails that are 6d (2 inches).
• Material: Hot-dipped galvanized nails are preferred to prevent rust, especially if the subfloor is exposed to moisture.

Tools:

• Drill: Preferably an impact driver.
• Nail Gun: If using nails, a pneumatic nail gun is commonly used for faster installation, while screws are usually driven in using your cordless drill.
• Circular Saw: Preferably battery operated as space and outlets may limited.
• Dust Collection: Keep that air clean, it’s important for your health
  • Shop Vac: For vacuuming up dust from circular saw cuts, and, connecting to your saw via dust collection hose.
  • Cyclone: Intermediary between shop-vac and tool, designed to segment out fine dust from reaching your filter.
  • Air filtration: Industry-standard level shop air-filtration designed to clean out small particulates.
    

Installation

Okay, if I might say, the subfloor was by far the hardest part of this operation. The attic is 3 floors up in an old Victorian with tight corners. There was no way to take a full sheet of plywood up the stairs. There was however a window on the second floor that we later found out we could fit blue board through, but we of course cannot go back in time now.

So, I had to get my 5/8th” smooth-faced plywood ( I went with the expensive stuff)  down to 2’x8’ sheets to carry them through the front door and up 3 flights of stairs. This was one of the hardest parts of the entire renovation. 5/8ths smooth is very heavy, and three flights of stairs is a long way to go. And to top it off, since we had a toddler and a new baby, I was mostly doing these lifts at night after 9:00 pm in the dark. I used a headlamp and it was tough to avoid cracking the ceiling with an 8’ board in the dark.

The first thing I did (as briefly mentioned earlier) was to lay them all on the same plane so that I had a corridor to walk and work from. From there, I took some measurements to see what kind of jenga I was working with and it turned out that I had two joists that lined up perfectly to fit two 2’x8’s side by side, which of course I could only do every other set so as to stagger the joints. This was in fact a lifesaver and cut my workload down tremendously. Why, you ask? Well because our joists are not 16” on center and are in fact a different width for every joist, averaging probably something like 22”.

Okay, with the jenga complete, we had a starting point to work from. Now, there are several key components to laying the subfloor including the right materials and positioning of the board. Additionally, if you’re working in an attic, you really should assess your layout (Jenga) so that your starting point is going to work with your future plans of where you want the plywood to end up.

So, on the materials front, we will want to talk about screws vs nails. Nail guns are faster, but, screws can be unscrewed. That said, if you’re going to use a nail gun, you’ll need nails that will do a better job holding the plywood down and that would be what’s called a ring shank. It’s recommended to use 2.5” ring shanks. This gives you enough depth to get both through the subfloor as well as the joist with enough bite to hold it.

For new construction and renovations, it’s standard practice to lay glue down on the joists prior to laying your subfloor. I opted out of the glue method for the following two reasons:

1. I wanted to ensure that if someone needed to pull these boards up one day, it wouldn’t be hard to do so and return them back into their original position.
2. I wasn’t worried about noise/creaking as we have super wide, dry, soft-edged beams and they really held the noise well, it was smooth.

Initially, I started off laying the subfloor with my nail gun but quickly switched over to screws. As mentioned above, I realized that it was going to be a lot easier to pull the subfloor up at a later date if needed.

To install blocking between floor joists, I first had to measure the distance between the joists to determine the length of the blocking pieces. From there, cut the 2×6 enough to fit snugly. The first few times, you’ll be too long or too short (better to be a hair too long), but eventually, you’ll move fast and get those cuts right every time. One thing to note for an old house like this would be that while most of these beams aren’t warped per se, they may be at an angle and thus, your blocking is not going to slide in perfectly every time – a few degrees off here or there is normal.

When installing the blocking, don’t come in at an angle through the blocking into the joist, come in directly through the joist into the sidewall of the 2×6. So, if you’re like me, you’ve got to shovel out all of that old cellulose, fire in your screws, and then put it all back. Use at least a 3″ screw here, preferably 3.5″ if you have old, wide joists like me which are nominally 2″.

One thing to note which is of the utmost importance (in line with not staggering boards) is to ensure that you allow for proper spacing between each piece of subfloor. This allows for expansion and contraction from hot/cold environments and any settling that might come your way in the future.

As I began to make progress on the subfloor, I started to open up my newfound clean, sturdy flooring for a new base of operations:

For the vast majority of the remaining workload, this would be home.

Fastening Tips:

• Spacing:
  • Screws or nails should be placed 6 inches apart along the edges of the subfloor panels and 12 inches apart in the center of the panel, along the joists.
• Avoid Smooth Nails: Smooth-shank nails tend to loosen over time, causing the subfloor to squeak.
• Adhesive: Use subfloor adhesive between the joists and the subfloor panels to add additional support and prevent movement and squeaks.