Mike Jay wrote:Hi Abigail, the beam (second picture) should be very strong so the floor right above that should be able to hold a lot of weight. The smaller boards running perpendicular to them are the joists. They look kind of small to me but it depends how long they are. How far is it from the beam to the next beam or outer wall?
I guess irregardless of that, the two joists underneath where you want to put your RMH have been severely weakened by the plumber (or DIYer) who ran the PVC drain through them. Those huge holes they drilled in the joists have pretty much ruined them. I would be very worried about even having a bath tub above those two joists. Empty tub would be ok but not filled with water.
I'd be tempted to have that PVC drain line moved down so it runs below the joists and then add a second joist alongside each of the existing ones. It's called "sistering" when you add a joist to an existing one to strengthen them. Sometimes it's easy to do, other times it's hard, depending on if there are wires or other things running through the joists. If you can strengthen them, the floor should be strong enough for a bath tub, dance party, or earthen floor. Maybe a RMH but it's hard to say..
Kenneth Elwell wrote:Everything Mike Jay said, and...Oh my gosh! That pipe drilled through the joists!!
So the rule is the hole can only be 1/3 of the joist depth and not within 2 inches of the top or bottom of the joist.
Abigail Abts wrote:So the joists run all the way across the floor, which I would say is about 25 feet. The big beam is about 7-10 feet from the exterior wall and about the same to the next big beam in the opposite direction (under the middle of the house).
I’m sure we will do some beefing up of those compromised joists either way, not the most comforting thought to have a weak infrastructure even if we aren’t adding weight upstairs. In the process of reinforcing those joists, could we do so in such a way that would make it more likely to accommodate the weight of a RMH?
Mike Jay wrote:
So if I'm understanding you, there are two big beams that run the same direction. And they roughly evenly divide the span of the joists? So each joist is only going about 7-10 feet before it gets to rest on a beam or the outside wall? If so, then they probably aren't undersized for the floor. They're smaller than mine, but my joists have to support 14' of floor.
It's great you can remove the pvc, that will make sistering joists a bit easier. If you can take more pictures of the joists in that area, we could give you some more ideas about how easily the floor can be beefed up.
Keep in mind, an earthen floor is adding weight so you may not want to do that until the floor support is fixed up a bit. And in fixing the joists, the floor might move up or down a bit which could flex the floor coverings.
Don't worry, we're here to help you figure this all out!