Floor under the DT issue

[awais98]

You are probably right about being overkill... Ill see what it feels like while Im at HD buying the lumbar.
A question, you mentioned about toenailing the top end. What do I do with the lower end on the cemented floor? I was thinking id need to drill in the fllow and toenail them there too. What do you suggest?

4x6s or 6x6s won't hurt anything, but in my opinion will be a lot of overkill. I would secure the two short pieces across the joists near the ends of the tank, you should be able to toenail into the bottom chord of the I-joist, then place the posts, tap in a couple shims at the top, and toenail the assembly together so the posts can't fall over if they loosen. Not really much to build, basically a T-post. In a few weeks when the lumber shrinks you may need to tap the shims in further, but IMO your fix is really this simple. Look at it this way, the tank is already supported, all you want to do is eliminate the deflection in the existing floor caused by the concentrated load of the tank.

 

[hllywd]

The idea of toenailing into concrete probably isn't going to be very successful... You can find post bases at Lowes, HD, etc... There are composite, and cast aluminum versions that separate the wood from the concrete preventing long term rot on a damp surface. Those normally do not have a physical connection to the concrete. There are also the sheet metal type that you would secure to the concrete with TapCons or something similar, then place the post in the base and screw through the provided holes. If it were me, I would wedge the post tight and call it good. Unless the posts are really going to see some action, once they're wedged in it should take a bit of force to dislodge them.

Post base examples:

http://www.lowes.com/pd_204539-166-...post&pl=1&currentURL=?Ntt=usp+post&facetInfo=

http://www.lowes.com/pd_58588-166-C...post&pl=1&currentURL=?Ntt=usp+post&facetInfo=

You can see the plastic one screws to the bottom of your post and does not physically attach to the floor.

Something I touched on was shrinkage and tightening shims after some time. Here we have a couple options for dimensional lumber larger than 2x, pressure treated, or cedar. The last pressure treated 4x4 I bought was wet enough I would have strained to carry two of them very far. I used it for a mailbox post so shrinkage was not critical. Even though it's far more expensive in your case I think I would choose a drier, more immediately stable option like cedar if it was available.

 

[sirreal63]

Using just a post will point load the basement slab, this is generally not a good idea. A point load needs to be placed on a proper base, which means an actual footer under the slab to help absorb and disperse that load. It may or may not cause an issue with the slab.

 

[hllywd]

Using just a post will point load the basement slab, this is generally not a good idea. A point load needs to be placed on a proper base, which means an actual footer under the slab to help absorb and disperse that load. It may or may not cause an issue with the slab.

No question If you were loading the posts heavily, however the intention here is to eliminate the deflection of the floor, not carry the weight of the tank. The floor system still carries the vast majority of the load. I'd compare the load these posts should normally see to the legs of a pool table sitting on the same slab, probably much less.

 

[sirreal63]

I don't completely disagree, however, without knowing the thickness of the slab it is a variable that has the potential to be an issue, which is why I brought it up. That point load is taking a portion of the entire floor system to one or two points on the slab, depending on how many posts are used. Loads transfer to adjacent joists so it isn't just the tank it is supporting, it is everything on the floor system. A wall does a much better job at dispersing the load than a post.

It may not be an issue, but the OP should be informed of the potential for an issue.

 

[awais98]

Thank you so much for your reply! Very helpful to me.

I didnt know post base existed, LOL, I was thinking about toenailing or L brackets. Thanks for the links.

I did hear about footing before, but I had assumed that would be if I had gone with permanent metal lally colums.

I am going to go with the 4x4 and those composite bases.
I hear you about the shrinkage, nice to know before hand.

More questions:
My current height from the joist base to cement floor is 103.5 inches:
i.e 8' 7.5"
Planning on 2 posts on each side of the sump, almost under the DT.
Im thinking about buying 2 4x4 of 10 feet height and cutting each to 8' 3", leaving 2 20 inches of 4x4 for the beams spanning over 2 joists.
so thats 8'3" post plus 1" for base and 3.5 " for the bean will make the required 8'7.5" height
I wont toenail tight the beam and post, so if and when it shrinks, Ill be able to hammer in shims.
Am I missing something there?
Thanks again!
Awais

The idea of toenailing into concrete probably isn't going to be very successful... You can find post bases at Lowes, HD, etc... There are composite, and cast aluminum versions that separate the wood from the concrete preventing long term rot on a damp surface. Those normally do not have a physical connection to the concrete. There are also the sheet metal type that you would secure to the concrete with TapCons or something similar, then place the post in the base and screw through the provided holes. If it were me, I would wedge the post tight and call it good. Unless the posts are really going to see some action, once they're wedged in it should take a bit of force to dislodge them.

Post base examples:

http://www.lowes.com/pd_204539-166-...post&pl=1&currentURL=?Ntt=usp+post&facetInfo=

http://www.lowes.com/pd_58588-166-C...post&pl=1&currentURL=?Ntt=usp+post&facetInfo=

You can see the plastic one screws to the bottom of your post and does not physically attach to the floor.

Something I touched on was shrinkage and tightening shims after some time. Here we have a couple options for dimensional lumber larger than 2x, pressure treated, or cedar. The last pressure treated 4x4 I bought was wet enough I would have strained to carry two of them very far. I used it for a mailbox post so shrinkage was not critical. Even though it's far more expensive in your case I think I would choose a drier, more immediately stable option like cedar if it was available.

 

[awais98]

Just out of curiosity, dont know the Physics behind it any more...
is 2- 2x4s more stronger then 1 4x4 for the posts? is there even a need of me to think about that?

 

[awais98]

Thank you for the information.
Every bit of info is helpful in making a sound decision. I appreciate you taking time to reply.

I don't completely disagree, however, without knowing the thickness of the slab it is a variable that has the potential to be an issue, which is why I brought it up. That point load is taking a portion of the entire floor system to one or two points on the slab, depending on how many posts are used. Loads transfer to adjacent joists so it isn't just the tank it is supporting, it is everything on the floor system. A wall does a much better job at dispersing the load than a post.

It may not be an issue, but the OP should be informed of the potential for an issue.

 

[hllywd]

The 4x4 is stronger since there is more material. To build up the same square dimension there would have to be a piece of plywood, OSB, etc... ripped and nailed between the two 2x4s. IMO doubled up 2x4s would be more than adequate strength wise, especially if you're going to have 4 posts, and the 2x4s will be drier and shrink far less. A downside is that without the spacer doubled up 2x4s won't fit correctly on the post bases.

This again is just my opinion, but I would lean toward the steel post base unless the floor is frequently wet and you need to keep the wood off of it.

 

[TomTheWicked]

2x4s will be drier and shrink far less.

I'm going to add that 2 x 4's are also less likely to twist and split.

Does the OP know how much the floor is currently sagging (if at all) under a static load (no kids jumping around it)? I would make sure that there's an acceptable amount of deflection in the joists before adding any permanent supports.

 

[Eud]

I understand the sistering but where does the 4x6 plywood help? i think it was not required. If you still needed more, you could have jus put some posts to support the sistering joists. IMHO

The plywood helps keep the joists from racking to the side like internal blocking would also accomplish. It also prevents the bottoms of the joists from stretching, which they have to do if they want to curve downwards from a heavy load placed above them. Curved line is longer path and all that.

The box made from the subfloor, joists, and plywood is very strong and spreads the load very well.

 

[awais98]

:fun2idnt realize that 2x4s would need a spacer in between to be same as 4x4... before i decide to buy 2x4 Ill check how they fit in the base, if its not good fit, Ill just get 4x4.
I am going to have only 2 posts total on each side.
Why would you use metal base instead of composite?
It said on the composite base that its 1inch elevated, and it would meet all codes. As I do not know what the codes are here locally, hence I thought, well, let it be that way.

Thank you for your replies, its been very helpful

The 4x4 is stronger since there is more material. To build up the same square dimension there would have to be a piece of plywood, OSB, etc... ripped and nailed between the two 2x4s. IMO doubled up 2x4s would be more than adequate strength wise, especially if you're going to have 4 posts, and the 2x4s will be drier and shrink far less. A downside is that without the spacer doubled up 2x4s won't fit correctly on the post bases.

This again is just my opinion, but I would lean toward the steel post base unless the floor is frequently wet and you need to keep the wood off of it.

 

[awais98]

You really got me thinking about the 2x4s now, :crazy1:

There is currrently no sagging at all under the static load.
The dt only sways about 1/4 inch too much for comfort when son runs around. The sway is normally not seen, only when you pay attention and see the waves or keep your hand on the DT

I'm going to add that 2 x 4's are also less likely to twist and split.

Does the OP know how much the floor is currently sagging (if at all) under a static load (no kids jumping around it)? I would make sure that there's an acceptable amount of deflection in the joists before adding any permanent supports.

 

[awais98]

Thanks for explaining. Makes sense.

The plywood helps keep the joists from racking to the side like internal blocking would also accomplish. It also prevents the bottoms of the joists from stretching, which they have to do if they want to curve downwards from a heavy load placed above them. Curved line is longer path and all that.

The box made from the subfloor, joists, and plywood is very strong and spreads the load very well.

 

[awais98]

Finally got the 2 4x4 columns and beam spanning 2 joists under the DT.
Feel better, finally wont yell when my son jumps walks :bounce3:









Have a question:
I had kept the 4x4s in the garage for a month so that it dries up completely.
I secured the columns with L brackets up and down, will that be an issue with contracting in winter??

 

[woodnaquanut]

Wood doesn't change much along the grain. Moisture effects cross grain size much more.

It looks like your 2x4s are not pressure treated. Those should be. Against the concrete and next to all that water, they will get moist and eventually rot.

 

[awais98]

Thanks for the advice again. Will change that 2x4 to pressure treated. I didnt know that.

I secured the 4x4 to that 2x4 to the wall. is that enough?
Seems to be enough but not sure, if I need to secure the 4x4 to the cement floor with L brackets ?

 

[sleepydoc]

http://www.lowes.com/pd_53421-166-B...entURL=?Ntt=4x4+post+base+brackets&facetInfo=

 

[woodnaquanut]

The product sleepyd recommended would be good. It provides separation of wood and concrete. If you have the ability to anchor in concrete, you could use that and not need the 2x4 at all.

 

[hllywd]

Wood doesn't change much along the grain. Moisture effects cross grain size much more.

It looks like your 2x4s are not pressure treated. Those should be. Against the concrete and next to all that water, they will get moist and eventually rot.

I would agree with the moisture point here if we were talking about older construction. Newer slabs, or basement floors almost universally have vapor barriers underneath that will exclude most moisture from coming through the concrete. I don't think you need to worry about the untreated lumber, I wouldn't. It's my opinion a post base would be better both aesthetically, and functionally, however again in my opinion what you've done is perfectly functional for what your issue was. I would say to monitor how the wood reacts as it dries, and if necessary shim under the post if a gap forms.