NWCO2

This may seem simple compared to working on a house but I don't want to do it and not have it work. I have a 20' W x 32' L one floor hunting cabin that I built. It's 20 years old and when I built it I skimped on materials where I probalby shouldn't have. At the time it was "good enough, nail it" Lets get it up and go hunting. The camp is on 15 piers. 3 rows of 5. The problem is that I framed the floor sils and joists with 2x6's. The sils are made of double 2x6s with a double 2x6 center beam. The joists are all 10' 2x6's 16" on center. I know everything shoud have been at least 2x8's and probably 2x10's. Now I want to take the movement out of the floor because it bounces and shakes if you stamp on the floor. There is a wood stove in the middle on one side and a heavy propane frig about in the middle over the center beam. Where the stove is the floor has sagged a bit but I can live with that. What I want to do is sister the joists,will this help. What size sister and best and easiest way to fasten. Not alot of room under camp but doable. Thanks in advance.

inspectorD

First off...welcome aboard.
Next thing, have you been under the cabin to check the condition of the joists. If they have any decay to em it may be easier to start over with the floor by sections.
Another thing is , check the beams where they are sitting on the posts, sometimes when the wood shrinks one of the posts has a big enough gap to cause the floor to bounce. I first jack the center beams to be level and shim them with pieces of steel.
The 2x6s are at their limit at 10 feet, but the beams can be the issue.
The next thing I would do is add a 45 degree post at each post , to carry some of the load closer to the center of the beam...if this is possible.

But to answer your question of sistering, Just use more 2x6s, yes it will be helpful to take out some of the bounce, but what I suggested is also easy to check and will also help.
Good luck...tis huntn season.

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Dan K

I have seen some cases where strips of 1/2 inch plywood where glues and screwed to the floor joist to stop bounce. this is primarily on engineered long span joist but could work in your situation as well.

joecaption

Far simpler to add some more 24" X 24" X 4" thick footings with rebar in them for new footings and block piers for a new double 2 X 8 beam running down the middle of each span. It also would make it possible to jack up the low spot in the middle before the final height of the piers.
Attaching 1/2 plywood would do almost 0 to help this.
Sistering more 2 X 6 joist will do nothing to left the floor back to where it needs to be. Even trying to beat them into place will be a real chore since the floor has sagged.
We work mostly on 100 plus year old houses and do this kind of thing all the time so I'm not just guessing on how to fix it.

EZHangDoor

You have already gotten the two best answers. In fact I was going to suggest both of them. Adding the beams to reduce the span maybe the easiest solution, it most likely will give you the strongest floor also. If you can cut the span if half again you would end up with very little deflection on the joist. As long as the beam is strong enough.

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BridgeMan

An easier and less expensive fix yet is to glue-and-screw 2 x 4s in the flat orientation to the bottoms of your floor joists. It's called increasing the moment of inertia (and section modulus) by adding bottom flanges. Works wonders for millions of bridges around the world, so it would probably work for your cabin.

Should be able to do 2 or 3 an hour, once you get the hang of it. With a material cost of less than $5 per joist.

EZHangDoor

That is a very interesting suggestion... and sounds like a great one. I assume this is the same engineering concept as I joists?

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NWCO2

joecaption,
This was my first idea but there isn't a lot of room under the camp to dig below frost level to get posts in let alone footings. I'd have to put in five posts per side and that's a lot of digging with not much room to move a shovel. I'm afraid if I put the footings on the ground or just below the frost will heave the floor. My other posts are at least 3 ft down.

Bridgeman,
I like your idea and it sounds simple enough. Do you run the 2x4s paralell along the bottom length of each of the existing 2x6s and form what would be a half of an "I" beam or do you run them perpendicular. I think you mean paralell. I also have no blocking or cross supports between joists either. Should I put in blocking? See attached pics of camp. THX

BridgeMan

Run the 2 x 4s parallel to the existing joists, centered on the bottoms. Doing so will stiffen things up considerably. And blocking won't do much to stiffen things up, unless you really want to go overboard with the size and attachment of the blocking members.

A million bridge girders can't all be wrong.

j23

I hate resserecting an old thread, but my current situation is on par with yours and I was curious to see what Avenue of approach you took and whether or not it worked?