rim joist nailing?

[CjAl]

do rim joists just get nailed into the ends of the floor joists or should i put angle brackets on the inside?

anyone havebone of nifty diagrams for building the floor system? my joists stick out past my beams so the rim joists arent sitting on the beams.

also if i dont find 20' joists and have to use shorter ones broken.over the center beam how do.i fill the gap onbthe ends where one joist will be set in where the outer overlaps it? do i.just glue and nal a piece to the side of it to fill the gap and bring it flush?

[John Raabe]

Normally the joists are trimmed so the rim joist sits on the beam or foundation sill plate and the rim is nailed into the joists and sill or beam. In a 20' wide building the the joists are shorter by the rim joist thickness.

[alex trent]

Where the joist overlap on the middle beam (assuming the joist is not long enough to span) you can just let them rest on the beam side by side. Or, you could cut to have them butt up to one another.  First option is a lot easier as less precise measures are needed.  If you go with simple over pal on the center,you need to remember as you nail to the joists that left and right side joists are not on the exact same center. Not a big deal...just remember it.

[CjAl]

my floor joists will run across the top of the beams and extend out 6".  i built my beams at 19'outside so that i can skirt the piers later. so there is no sill for that header joist to sit on.

am i okay to just nail the rim joist to the end of te floor joist since its not supported from below or did i mess up and i just made myself a 19x32 instead of a 20x32?

[alex trent]

Your wall needs to be above your beams.  Not sure if you can get away with 6" cantilever, but I think not.

[CjAl]

i am sure i read you can overhang by up to as much as.your joists are wide. but dont ask me to show where i read it in here.

[CjAl]

i could build it 19 wide, no problem except the headach from hitting myself in the head with the hammer. i need that extra foot to meet my minimum square footage. i could add it to the loft or the screened porch i guess

[CjAl]

where is DonP when i need him?

[MountainDon]

You can build with a cantilever equal to the depth of the joist with no issues. No guessing; says so in the IRC even. BUT, the thing I'm not sure of right now is what happens with that when the floor joists are not continuous from one side to the other. I believe you want to rely on more than the weight of the center portion of the floor to prevent the rim ends of the joists from moving down as any down moment at the outside will have an upward moment at the interior end of the joist. Hopefully Don_P will share some wisdom on this thought. I'd have to read/research the answer and there's no time tonight.  The connection of the floor joist to the center support beam must provide whatever uplift resistance is needed. What that is is the question?  A guess is that several properly nailed toe nail connection, joist to beam, will suffice.   The "towards the interior" leg of the cantilever will be much longer than the short 6 inch cantilever, but if you follow the way levers work.....     When the outside walls sit over the beam that issue does not occur.


Rim joists like you describe will be supporting some weight from the side walls and roof if you look at a cross section load path. A solidly nailed down sub floor will help tie the rim to the joists. IF there will ever be something like a deck/porch added to the building side that deserves some thought during this planning stage.

A few nails through the rim into the end grain of the floor joists provides little pull out / lateral resistance. Use of joist hangers along the rim could provide more lateral pull away resistance.
It's not mentioned in code but I wonder if using a joist hanger turned upside down on the rim would provide any advantages when thinking of carrying loads down through the wall framing to the floor joists and hence to the main beams? 

The sub floor sheathing along the side walls should be full width sheets if possible. Half sheet would be a good idea as an absolute minimum width; never a narrow strip. I mention this as using most T&G sheet products will result in a shortfall in width as most T&G sheets are really covering 47 1/2 inches. ... Or do like I did and make the building slightly narrower than 20 feet. The wider sheets will give more strength to tying the rim to the rest of the structure.

If there is to be a deck/porch added on the side with the rim used as a support a doubled rim would provide more thickness if lag screws or Ledgerloks were used for the deck to rim connection. Along that thought would the addition of a deck/porch overload the beam or footings? Bolting through a rim using machine bolts, washers and nuts is superior to any screws. Easy to do if planned properly. Don't use carriage bolts for the connection.

[CjAl]

thanks mountainDon, i was starting to second gues myself and i couldnt find where i read the information.

i could add some 90 degree angles to the rim joist to floor joist connection if need be.

as for overloading the beams i doubt it. i have three beams. tripple 2x12 on outer two and double 2x12 on the middle beam. i have added five more piers then the story and a half plans call for on that center beam, there will be a ridge beam with direct connections to the end two and center piers in the middle. my piers are all on a 18-24" round footing at least 6" thick. so i believe i figured in enough extra support for the porches. there will be a front porch full width hung to one rim joist and a rear porch probably half the length of the house on the other rim joist.  so you think i should double up the rim joists?

if i double them it would give me 6" of overlap in the middle if i do split the floor joists, if i do a single rim i am right at the minimum overlap of 3".

i can get full length joists if need be i would just have to have them delivered instead of picking them up myself

[CjAl]

btw

if i do split the joists i have enough of these simpson hurrican ties to put one at each end of the joists. one on front beam, two at center beam and one on rear beam. 100 total. i also have some of the one sided ones for the end joists where one side of these wouldnt have any beam to attach to.

[PEG688]

 Full width joist would be a good idea  , or  center bearing partition.

Solid block over the beams.

Stay away from engineered "I" joists.

Use H-1 rafter ties to tie the joist to the beams to resist uplift.

The full or minimum 1/2 width sheets on both edges would be a good idea.

BUT I've never seen a rim joist ripped off the joist ends in my life, never heard of it either , but I guess it could happen.

I'd just use my wall sheathing to tie the walls to the rim , let it hang down when you sheath the walls , makes a big gusset.  The wall sheathing tied continuously , or substantially from wall to bottom plate , to rim joist , better yet all the way to the sole plate ( which in your case you don't have) would make ripping the rim joist off the joist ends almost impossible for any natural force of nature.   AND IF NATURE DID apply that much force the building isn't going to survive , nor are any people in the area likely to survive either!   

  KISS , tie one thing to another well , are things well remain together in most normal situations.

[PEG688]

btw

if i do split the joists i have enough of these simpson hurrican ties to put one at each end of the joists. one on front beam, two at center beam and one on rear beam. 100 total. i also have some of the one sided ones for the end joists where one side of these wouldnt have any beam to attach to.

IF you're going to use two joist they should by pass either other by about a 12" and be well nailed together at the lap , blocked over the center beam , and toe nailed down to the beam.

You could use H-2.5 to then connect the joists to the beam , but at mid span with the sheathing over the top and interior partitions and such I wouldn't bother with any Simpson hardware at the center beam.

[CjAl]

are you saying you wouldnt bother with simpson brackets on the center beam even if they are two piece? or only if the joists are one piece? i have some h2.5's but not 50 it would take to do them all and the h1 wont work with a 12" overlap. i thought 3" was minimum. i guess i could get 12' for joists and cut 14.5" off each for blocking. the remaining would give me almost 2' of overlap

there will be a central partition wall helping to support the loft but it will only be over half the house (16')

[CjAl]

that 12" of overlap has me kinda bummed out. lowes has 2x10x10 for $5ea right now anythin in 12' either 2x8 or 2x10 is pretty much almost double the cost

[John Raabe]

Lapping joist over the internal beam keeps the shrinkage of the joists and floor system more consistent over the span. Also, when you have beams right under the subfloor you can  run into problems routing drain pipes in the walls.

[PEG688]

that 12" of overlap has me kinda bummed out. lowes has 2x10x10 for $5ea right now anythin in 12' either 2x8 or 2x10 is pretty much almost double the cost

  Well you'll pick up 3" from the rim joist , so get as much over lap as you can ,  keeping in mind the 2 feet you mentioned would be to much over lapping, with crowns on joist 12" is about all you want or you get goofy things happening at the over laps, bumps, humps etc.

What you could do over the living room is the inverted joist hanger trick , use  a 2 x12 hanger on a 2x8 joist , I'm sure there's no testing done on hardware used this way. With the 2x10 you'd have to look for a longer hanger or some strap you could wrap up  over and back down  the other side.

20 foot joists would be the best situation.     

[CjAl]

ya i will have to run over monday and see if my local yard carries 20' lengths. they surprised me by having the 2x12x20 treated in stock. lowes doesnt carry anything 20'

[Squirl]

3" is minimum.  I passed my floor inspection with it. You pick that up from the rim joists.  All my lumber was 1/4-1/2 inch over length too.  So that was a little extra. 

I prefer to sister the joists rather than running a single 20 footer for a few logistical reasons.  A single 20 footer is a lot more difficult to handle and transport to the site.  In my limited experience finding good straight lumber that is 20 ft in length is difficult too.  Also with the crowns and slight variability in your built up beams trying to get one piece of wood to lay perfectly across three beams is probably going to have problems.  Take a look at the Oregon 28x38 universal w/shed addition pictures that were just posted.  They used I-joists which are usually straighter than dimensional lumber.  Trying to span over three points they had to notch and chisel the center to get it to lay across all three evenly.  This is not to pick on the build, it is simply a normal step when dealing with wood and this method.  While this is not impossible to overcome, it is just an extra step with more work. 

When sistering, if you have a slight crown in any of the beams and the joists are uneven by 1/4" you will never notice it after the subfloor is on.  I've had boards crown and warped more than that.  There is also less cutting.  You will have to cut 3"-3.25" off every 20 ft board for the rim joist.  With sistered joists all you have to cut are 2-3 end joists.

[PEG688]

3" is minimum.  I passed my floor inspection with it. You pick that up from the rim joists.  All my lumber was 1/4-1/2 inch over length too.  So that was a little extra. 

I prefer to sister the joists rather than running a single 20 footer for a few logistical reasons.  A single 20 footer is a lot more difficult to handle and transport to the site.  In my limited experience finding good straight lumber that is 20 ft in length is difficult too.  Also with the crowns and slight variability in your built up beams trying to get one piece of wood to lay perfectly across three beams is probably going to have problems.  Take a look at the Oregon 28x38 universal w/shed addition pictures that were just posted.  They used I-joists which are usually straighter than dimensional lumber.  Trying to span over three points they had to notch and chisel the center to get it to lay across all three evenly.  This is not to pick on the build, it is simply a normal step when dealing with wood and this method.  While this is not impossible to overcome, it is just an extra step with more work. 

When sistering, if you have a slight crown in any of the beams and the joists are uneven by 1/4" you will never notice it after the subfloor is on.  I've had boards crown and warped more than that.  There is also less cutting.  You will have to cut 3"-3.25" off every 20 ft board for the rim joist.  With sistered joists all you have to cut are 2-3 end joists.

You're not cantilevering either.  The reason the other poster would be better off with the 20' joist is the cant he wants to run.   

[MountainDon]

The reason the other poster would be better off with the 20' joist is the cant he wants to run.   

The was the main point I was trying to make in my post (reply #8) 

[Don_P]

The building code is silent on uplift and backspan requirements when the overhang is less than or equal to the depth of the joist. The load can flow to the support at a 45 or steeper angle. The minimum backspan ratio in the cantilever table is a 3:1 ratio, this is in the neighborhood of a 10:1. In other words the seesaw would have to be really loaded out there for uplift at the center girder to be a problem. Solid blocking between joists or lapping joist pairs is a good idea as are H2.5's or 10's if they do fit.

A deck connected to the overhanging rim is not allowed, it should be built as a freestanding floor on its' own piers by code. I have seen the upside down hangers from main joists to rim before, you are getting into really loading the rim though and if this is over girders I'd bet that load has not been accounted for, more reason to make it freestanding or put a foundation wall under the rim.

Long overlaps over the center girder sounds good at first blush, mentally I believe we are thinking we are weaving a continuous joist back together with a long lap. What really happens is that thes overlapping ends kick up when their main span is loaded, a squeeker. I was taught to limit that overhang to no more than about 6" beyond the girder, nothing hard and fast just a general consideration, it becomes 2 simple spans pinned over the girder rather than a continuous span (the load reactions do change).

[CjAl]

okay so no porch hung off a cantalivered rim, thats good info.

could i hang the porch off the beam instead and run it under the rim? that would leave me a step down to the porch, i like that since i want to get the porch lower since i would like one or two wide steps to the ground so i dont need railings

one of thebporches will be a screened porch so it will have to be attached at some point

[Don_P]

Structurally that's fine. The step down is not allowed to be greater than 7-3/4" unless there is a landing at least the size of the door served (A 3'x3' landing outside the door minimum if steps are needed to get you down to the deck). I have mixed feelings there. I made a 6'x 16' landing, 2 steps across the face three down to the sides to tiered decks. I was trying to catch the grade and be "arty". Decking directions switch as a visual cue. Still my MIL took a face first header off those step downs, you know how I felt, it is not normally expected I guess.

Do check the girder's capacity and I would want for it to be treated, water will probably drive back in there occassionally.

[CjAl]

you probably have a point there. my wifes grandpa is 90 and we had to add a railing to the porch for him and his wife. something to consider.

i could do it with an 8" floor joist and keep the step down under 7 3/4".  i suppose i could build it self supported and just attch the wall studs for the screened in area to the side of the house, the roof would be attached too.