Floor reinforcement - Will it be enough?

bean2986 · Apr 29, 2017

Hello all,

I'm prepping my floors for my new 180 + 75 sump. My only option is running parallel to the joists so I invested in an evaluation by a structural engineer. His recommendation was sistering all joists under the tank to make all 2x8 beams triple sistered over the 12 foot span.

Has anyone done something similiar and supported all of their larger tank weight on sistered parallel joists? Im still concerned with deflection and the tank bouncing even with the extra beams and the recommendations. Running posts to the ground is also not possible since the basement will be finished. I attached a photo of the subfloor/ joists for reference.

Any input or shared experiences would be greatly appreciated!

Brew12 · Apr 29, 2017

bean2986 said:
Hello all,

I'm prepping my floors for my new 180 + 75 sump. My only option is running parallel to the joists so I invested in an evaluation by a structural engineer. His recommendation was sistering all joists under the tank to make all 2x8 beams triple sistered over the 12 foot span.

Has anyone done something similiar and supported all of their larger tank weight on sistered parallel joists? Im still concerned with deflection and the tank bouncing even with the extra beams and the recommendations. Running posts to the ground is also not possible since the basement will be finished. I attached a photo of the subfloor/ joists for reference.

Any input or shared experiences would be greatly appreciated!

I think you were given good advice. You may have a 12 foot length but I'm guessing you will have a 6ft length to spread that weight over. Triple beams, properly installed, should allow for minimal deflection.

SteveSTL · Apr 30, 2017

If the engineer put his seal on it, it will be enough. Just be sure that the sistered joists are touching top and bottom, use nails not screws (unless shear rated), use a solvent based glue not water based (water based can creep over time), and use quality bolts - not Home Depot ones.

bean2986 · Apr 30, 2017

SteveSTL said:
If the engineer put his seal on it, it will be enough. Just be sure that the sistered joists are touching top and bottom, use nails not screws (unless shear rated), use a solvent based glue not water based (water based can creep over time), and use quality bolts - not Home Depot ones.

Yeah He told me all of that as well. He also said #2 lumber from HD would be fine, but I'll be buying the best I can within reason from a lumber yard. Not sure I will go as crazy as LVL but depends on price.

SteveSTL · Apr 30, 2017

Absolutely no need for LVL. At a decent lumberyard, #1 will be cheaper than HD anyways. If you want peace of mind, go out 1 more joist on each side than what he specified. You'll be able to park a BIG truck on that.

bean2986 · Apr 30, 2017

Good to know! I haven't gone shopping yet so don't know prices. What about using 2x10 to sister the 2x8 and notching? Worth it? My main concern is bounce at this point.

Brew12 · Apr 30, 2017

bean2986 said:
Good to know! I haven't gone shopping yet so don't know prices. What about using 2x10 to sister the 2x8 and notching? Worth it? My main concern is bounce at this point.

Stick with the 2x8's imo. Your engineer gave you over 2.5x the safety factor with his suggestion, which is fairly standard. As long as you do the 2x8's you will be just fine.

Flippers4pups · Apr 30, 2017

I sistered mine under my tank the 6ft length. Liquid nails and bolted (way over kill). I also placed a 4x4 under the length and placed steel adjustable posts at each end to keep the "bouncing" in my living room down when my grand kids come over. Lol. Picture is from when I was building the sump two years ago.

bean2986 · Apr 30, 2017

Flippers4pups said:
I sistered mine under my tank the 6ft length. Liquid nails and bolted (way over kill). I also placed a 4x4 under the length and placed steel adjustable posts at each end to keep the "bouncing" in my living room down when my grand kids come over. Lol. Picture is from when I was building the sump two years ago.

Honestly I wish I could do that exact set up with sump downstairs but I have been strictly forbidden from bringing posts to the floor OR drilling holes in the floor.