Hi All,
So I have an early 90’s home with 2 x 10, #2 Douglas Fir Floor Joists spaced 16 on center spanning 13.5 feet on either side of the main beam. The topsides are glued and nailed to the plywood sub-flooring above. The original owners decided to finish the basement. Great idea! They installed a drop ceiling and unfortunately, to make room for 2×4 drop-in light fixtures, they pushed a 1 inch heating line up into the floor joints by way of a 2″ x 2″ notch smack in the middle of each span. The floors do not appear to have moved at all over the past 30 or so years but I am now looking at installing granite counter tops and am thinking about the extra weight on the notched joists. I’m looking for any ideas to mechanically bring the 2×10’s back to their original strength. I really do not want to remove the ceiling to sister in new joists. Any help anyone can give will be greatly appreciated.. Thanks.
Replies
With the 2x2 notch - in the middle, underside of joist, you effectively have 2x8 joists. Span tables below will advise based on 40# deadload. You have more than that. Table doesn't even consider spans longer than 12'-10".
https://www.awc.org/codes-standards/spantables/tutorial
Frankie
Right. Thanks for the reply. Im looking for ideas for a fix though. Preferably one that does not involve taking down the ceiling, removing wiring and plumbing lines and sistering 20 or so 2x10s.
You don't have many options even if you remove the drywall and you have none if you don't. It's not like you can glue a filler in the notch and call it done. How many are notched?
You can either sister every rafter or put a beam under them.
How do you expect to fix the hidden joists without removing the ceiling? Laparoscopic joist repair has not come to home construction.
I'd replace the 2x4 light fixtures with a new style of recessed lighting. Commissioning an engineering report would determine the length of overlap needed on either side of each cut-out. It would specify the fasteners and their spacing in addition to gluing requirements. (HVAC installers cut through 2 joists in my home and I demanded an engineering report for their repair.) You could also explore metal strapping fastened to the lower edges of each joist, but again you'll require an engineering report.
I believe some ceiling panels contain asbestos. You might want to check it out before you start demoing that ceiling.
https://joistrepair.com
These folks would be worth a call
That could be a lifesaver there! I love construction technology!
I've worked in a lot of old houses whose joists were hideously over-spanned by today's standards. And yet they still function. What I might do in your case before rebuilding the floor system is to determine if there's any real problem. In fact, it's unlikely you'd ever have a catastrophic failure. Most likely you'd get too much deflection, which might affect tile or stone flooring.
First, where are the countertops going? Weight in the center of the span will have a greater effect than weight at the ends. If it's just perimeter cabinets, I wouldn't worry much. If there's to be an increased center load, I'd mimic it and measure the actual deflection. The minimum code standard for allowable deflection is L/360, that is, the span divided by 360. Set up a laser at the edge of the room, and mark the height of the laser beam on a story pole in the center. Then load the floor where the granite will go with an equivalent weight of something like sand. Account for other weight such as people and dishes - Maybe double the weight of the granite. Spread it out over the actual area the granite will cover. Now mark where the laser is hitting the story pole. Measure the distance between the marks. If it's more than the the L/360 number, then consider beefing up the joists. If it isn't, I wouldn't lose any sleep.
Great advice, thanks a bunch!
Need to install a beam and a post.