Subfloor strength for large tank

[Ashish Patel]

I would add a few joist hangers to sure up the mounting. And I would do like the picture.

Thanks, this would make life easy using something like this.

 

[redfishbluefish]

My first thoughts....

1. Add additional I-Joists and use the hangers shown in an earlier post. Note that I-Joists can not take point loads, so anywhere there is a point load, you need to add squash blocks (some call them crush blocks).

2. Blocking actually transfers load to adjoining joists, so block the joist together will assist in transferring load across the floor....even those joists that are not directly below the tank.

3. And for 400 gallons, I would do something similar to what is shown above with the steel I-Beam. Note that steel isn't necessary for such a short span. Either a triple wood beam or LVL would work just fine...with two jack posts per beam. Don't try to get away with one jack post in the center of the beam....you've just created a lever and fulcrum, and you know what happens with them. And, as stated earlier, you'll need to apply squash blocks where this beam contacts the I-Joists.

Best of luck....keep us informed.

 

[pdxmonkeyboy]

I have shored a couple different floors up for LARGE tanks, so here is some helpful information.

Get two 2x8, put a TON of glue on them and then screw them together. You want 2 screws every 6". The 2x8 should be long enough to support at LEAST one joist outside of the ones under the tank.

Then buy some strapping.. the cheapest is the metal plumbing strap from home depot.. the one with all the holes in it. Cut two strips a couple feet long off and nail them to the joist where the approximate ends of the brace will be.

A friend lifts the brace into place and then you pull the strap around and nail it to the joist, thus holding the brace in place.

Now, get your flood jacks...https://www.amazon.com/Tiger-Brand-Jack-Post-JS-15/dp/B001B15DEU/ref=asc_df_B001B15DEU/?tag=hyprod-20&linkCode=df0&hvadid=198091670152&hvpos=1o4&hvnetw=g&hvrand=15876960235714396235&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033603&hvtargid=pla-350445345259&psc=1

and place them on top of a patio brick or post base (the concrete pier things at Home depot.). Don't just place them on the dirt.

Tighten them up until you start to hear the floor creek. If you live in an earthquake area I would put a couple of these in. There are twisted 90 degrees for fastening perpendicular joists.
https://www.homedepot.com/p/Simpson...QakC-Bs8fUDwmwJzjfhoCrkAQAvD_BwE&gclsrc=aw.ds

 

[pdxmonkeyboy]

The plywood in between the 2x8's will prevent any sagging/warping and increase the strength of the support immensely. Glue and screw them all together to make a solid support.

The plywood in-between the beams does not actually decrease sagging "immensely". It typically increase stiffness by about 10%. That is a common misconception. The plywood is typically added so that the width of the beam matches standard 2x4's.

I mean, its not going to hurt anything but it doesn't really up the strength of the beam.

 

[Ashish Patel]

My first thoughts....

1. Add additional I-Joists and use the hangers shown in an earlier post. Note that I-Joists can not take point loads, so anywhere there is a point load, you need to add squash blocks (some call them crush blocks).

2. Blocking actually transfers load to adjoining joists, so block the joist together will assist in transferring load across the floor....even those joists that are not directly below the tank.

3. And for 400 gallons, I would do something similar to what is shown above with the steel I-Beam. Note that steel isn't necessary for such a short span. Either a triple wood beam or LVL would work just fine...with two jack posts per beam. Don't try to get away with one jack post in the center of the beam....you've just created a lever and fulcrum, and you know what happens with them. And, as stated earlier, you'll need to apply squash blocks where this beam contacts the I-Joists.

Best of luck....keep us informed.

Redfish -

Thanks, Very nice suggestions...Are you saying add 2 LVL parrellel to the tank /supporting the subfloor directly or perpendicular to current floor joist? I have to look into the Squash blocks and all. I do plan on overbuilding this thing so there is no chance of movement.

 

[redfishbluefish]

Redfish -

Thanks, Very nice suggestions...Are you saying add 2 LVL parrellel to the tank /supporting the subfloor directly or perpendicular to current floor joist? I have to look into the Squash blocks and all. I do plan on overbuilding this thing so there is no chance of movement.

What I'm saying is that the steel I-Beam shown here:

can be replaced with an LVL. With the tank over 3 I-joists, I'd have the LVL perpendicular to a minimum of 4 I-Joists. Use two of these LVL's with two jack posts on each LVL.

Here's a diagram of squash blocks application (of new construction)
on a point load of wall above and wall below.

Because you really don't have a point load directly above...and this might be a bit of overkill....but I'd have a tendency to sister your I-joists with dimensional lumber on at least one side of the I-joists, the distance between the two LVL, with a point load squash block on the opposite side where it meets the LVL. I hope that description is clear. And because this is post original construction, I wouldn't worry about the squash blocks being 1/16 longer....just fit them snug...tapping them in with a hammer, and then nailing to the I-Joist.

 

[Ashish Patel]

Makes sense now..I think I am confident with this project now. I may even add 2 additional joist (8feet), just to be triple safe.. Thanks

 

[Ashish Patel]

Closing tomorrow, Exciting times and even more excited to find 2 load bearing walls. My tank will be on or between these 2 beams.

Now I am thinking I may just be better off putting some extra joist and call it good. What does everyone suggest?