Should the subfloor be laid perpendicular to the floor joists or does it not matter as long as the seams hit the center joist?
Asked by Hugo Clarke 
4 months ago
Last Updated: July 26, 2024
I’ve got a question about floor joists and subfloors. I’ve always heard that the usual way to lay a subfloor is to have the 4×8 sheets perpendicular to the joists. But does it really matter as long as the seams line up with the center of the joist? Just curious!
It’s best to have it placed perpendicular, if you can manage it. This ensures that there is support across the full 16″ x 8 foot area. However, in a house with normal climate control, using the parallel method could work as well. I’m interested to hear other opinions on this.
– So, I’m dealing with a small room in a house from the 1800s. The subfloor made of tongue and groove 1x3s has rotted in one spot. I’m in a bit of a time crunch and my plan is to only replace the damaged section while keeping the new 4×8 tongue & groove intact for potential future additions. Does that sound clear? To pull this off, it would need to be laid parallel.
Hey , in my opinion, if it’s just a small section of an older house, I believe it should be okay. I believe the rule applies more to newer homes built with much lower quality materials compared to what your house has. The quality of your wood is far superior to today’s construction grade materials.
I wish that were the case for this area. Moisture has managed to seep under the home and caused the floor to rot. Additionally, the joists are spaced out at 24 inches, so I’ll need to add extra support. Now I’m concerned that the other floors might also require similar repairs.
Hey , I’ve actually done that type of patching on a single board basis before, and I believe it will turn out just fine. If you’re really worried about support, you might want to consider adding some cross-joist supports to reinforce your subfloor. You could try installing some 2x4s to increase stability.
On another topic, I once had a house with moisture issues stemming from underneath, and it was a much newer home. The problem lay in the fact that the crawl space wasn’t properly vented, causing moisture to accumulate beneath the house and causing me quite a bit of trouble. If you’re going through a similar issue, I would recommend consulting a general contractor to ensure proper ventilation under your house.
Yes, it can make a big difference, especially when using CDX “real” plywood. You can actually see a strength axis printed on it. Just by walking on it, you can notice a difference in strength. Walls can be laid in different directions without any issues, but floors cannot.
Hey , I have a husband who tells me things I don’t want to hear too! 😂 Just kidding, I already knew this but didn’t want to admit it. I’m using the usb T&G subfloor. Do you think that would make a difference?
Hey , if this is the first layer and it’s directly fastened to the joists, make sure to run it perpendicular. It’s also a good idea to use plenty of subfloor adhesive to prevent squeaks.
Always go for the perpendicular approach. It adds strength to prevent any potential collapsing. Just imagine strong winds hitting a house made of cards.