Floor joists in new construction

[speelmans]

We just got the blueprints to build our home. However, there are no detailed plans for the joists of the first floor. Can anyone tell us how to read these blueprints? Or do you know what resources there are to find this information? Thanks!

[Rich]

Typically - prints will include full framing drawings with details. I guess short of charging you $60 / hr to draft up some drawings - I would say go to your LHS and see if they are capable of providing a service of take-off or layout.
Without seeing your blueprints I have no idea how to tell you what's there. :) I would say search Google or Amazon.com for blueprint reading or something.

[speelmans]

Hi Rich, thanks for the info! What's weird about our blueprints is that it shows framing for the second story and the roof, but not for the first floor. So we're unsure of how to actually put the joists together to make sure that the floor will be adequately supported. Also, I'm a novice at this housebuilding stuff...what does LHS mean? haha

Hmmm...I would be happy to provide you a link to the house that we are planning to build if you could assist me in any way with my questions.

[mreynolds]

I learned how to read prints about a year ago, basically I found out by asking several different people and reading books. For instance, you could go to your local building supplier and ask them about specific details of your plans. Generally they have a pretty good idea. The more people you ask, the better. The unfortunate thing is that everyone has their own spin on how to do things, so be prepared, the architect, the building supplier, the contractor may each have a different idea of the "right way" to do things. This is where you as a consumer have to really do your homework and decided what you want to fight for what you will let go to the professionals. Blueprint can range from the really specific to the extremely vague, good luck.

[Rich]

If you look at your post LHS is highlighted in RED - and throughout there are some items highlighted in red - mouseover them for a few seconds and you'll see what it means. LHS - Local Home/Hardware Store.
If you put up a link I may be able to help with some framing. I wonder if that drawing was missed in drafting or shipping or something. Weird that only that floor would be missing. Oh - could they call it basement reflected ceiling plan maybe??

[roger g]

Maybe it's slab-on-grade. Therefore.......................(drum roll)....no first floor joists.

roger

[Rich]

LOL that could be very true. The obvious is usually the hardest to see. I'm not saying that's your case speelmans - but it could be. I never reallly think of that because I've rarely done a home with a SOG. Typically a basement or a crawlspace.

[speelmans]

OOPS! I didn't specify that it does have a full basement. So no SOG for us! LOL If it were a slab, I think my question wouldn't have been necessary, Roger. :P

Let me show you the plan (I hope this works). http://www.lowes.com/lkn?action=frameSet&url=hdaplans.com/lowes/main.asp

[Rich]

Apologize for that - we have to assume that users have no idea what a slab on grade is or anything else for that matter.. and then go from there. :)
Anyway - that link just goes to the home page of their plan center. Do you have a plan #?
I was looking through what their blueprints include and it does say that they include a drawing with placements of beams, etc.. for each level of the home - but not specifically called out as a floor framing plan.

[roger g]

I've got an idea! Why don't you forget about looking for the size and spacing of the floor joists and go to the supplier of "silent floor joists". If I was to build a house again I would use silent floor joists. They are a made up joist with the web made of plywood and the top and bottom chords made up of 2x4 or something like that. They span incredibly long spans without support and come with knock outs to easily run wires. Your entire basement wouldn't need one post or support wall. A sight to behold if you have never seen one big huge, wide open basement. The silent floor supplier will properly size and spacing for your home without charge so it doesn't make any difference what is or is not on your plans. Silent floor joists also come with engineer papers which really make the building inspectors happy.

roger

[Rich]

Yes - I agree roger. Trusjoist McMillan makes TJI's which are incredibly easy to install. You can see their design brochure by going to www.trusjoist.com And what roger says about them designing a floor system for free is true. They want to sell their product. I would also have them do the rest of your floors the same way.

[metolius]

Our local lumber suppliers forward a copy of floorplans to Bosie Cascade or Truss Joist and the provide an engineered plan with a take off list that we can submitt to city and county plan review. you might check with your local lumber suppliers

[jjcold]

speaking of floor joists, I was going to post a new thread about this, but instead will just tailgate onto this one. Hope that's okay.

My new house has the TJI engineered floor I-beam joists you speak of. I though that now everyone used them. I think they were spaced correctly, I didn't measure them but from memory they look to be spaced 16" on center. Certainly no more than that. Does that sound likely?

Anyway, my house has a bit of floor bounce in certain areas. Of course it will, but my question is: Does it take a while for a house to settle down on its foundation, posts, etc.? Will that make the floor seem more solid? The longest span from front to back of the joists is about 31'. there is only one center beam in the middle of that span. The joists are 10". I would have preferred two center beams. Is it possible, or foolish, to add one later?

[roger g]

Bounce huh! I wouldn't want any bounce. What happens if you have a small party! The type of special floor joists we were talking about doesn't have any main beam under it let alone two. I think I would be doing some measuring and then find some engineering specs of your joists to see if it was done right. Maybe you just need some extra bridging. Floor joists are not always spaced like studs every 16 inches, sometimes every 12 inches depending on location. Someplaces in the floor they may be 12 inches and others 16 inches. Places like bedrooms and bathrooms are usually not so active.

roger

[Rich]

Sometimes TJI type joists are engineered at L/240 for deflection. This makes the joists pretty shallow - whereas a floor designed at L/360 or L/480 have less bouce or deflection.
Just looking at the TJI catalogs for a 9.5" deep joist at 16" o.c. with a L/480 deflection limit - it can span 16'3". At 19.2" o.c. you're looking at 15'4". So something doesnt' sound right. L/480 is damn good deflection limits - very little bounce.

[jjcold]

Well, perhaps at this point I need to ask, what exactly is "floor bounce"? My floors don't really deflect, It's just that when I jump up and down on them in certain areas, I hear *some* vibration, not a dead thump like you would on a concrete slab. I've noticed this in other houses, too.

[roger g]

If you have jumped in other houses and you think it's the same then it's probably okay. I'm 200 pounds and if I jumped and landed hard on my feet then I would expect a picture would move slightly on the wall but I would not expect to hear or see anything if several people just moved around the room. I don't expect people to have to "breakstep" just walking around.

roger

[Rich]

Floor bounce, as demonstrated in my own home, is similar to when you jump up and down in the center of a room and the entertainment center against the wall kind of rocks towards the center of the room..hah.
As far as thump - that may be due to insulation in some areas or not.. unlikely but you never know. Otherwise - it's just the nature of wood framing, unless it's really really bad vibration then there may be some problems.

[jjcold]

Well, I suspect it's okay. I was concerned since I had this floor plan extended 2 feet in the long direction of the floor joists. I also still hear alot about blocking on floor joists, and I don't think that was done on mine. Is that still done on silent floor I beams? If that would help, is it possible, or make that... feasible... to do it later?

It isn't bad when people just walk around on it, though in places there seems to be a little noise if kids run on the floor. Other wise it's fine. I'm a big guy, too, so I suppose I'm gonna get some action if I start jumping up and down on the floor!

As always, thanks for all your help. This is the best place on the web for those of us having a house built to ask, "Hey, what's up with this???"

[jjcold]

BTW, Rich, does that entertainment center thing really happen in your home?

[Rich]

Yes it does happen. Floor is framed with 2x10's. Scares me when I empty and fill a 30gal fish tank.

Mid-span blocking does help quite a bit with movement of the joists and "bounce". If you look at the TJI brochure at www.trusjoist.com if will tell you exactly where and how to put blocking in.