Framing & Code & Help

Try posting some pictures of the ceiling area where you are trying to build your wall and that might give the folks here a little more to go on.

I built all my walls by framing them on the ground a hair short of the needed height, flipping it up into position, powder nailing it to the slab, level it, shim the top and nailed them to the joists.

It would be very helpful to know the city/county/state where you live so those very familiar with local code can pipe in. When you bump into such interesting requirements, it is useful to you to pursue the matter with the building planner...such as "why does the floor above need to flex" and "how do you suggest the top plate be secured". Understanding 'why' the requirement exists will go along way: (a) in making certain there is no miscommunication going on; and, (b) to providing ideas and methods to address the issue.

There are any number of products available from www.pac-intl.com and www.kineticsnoise.com that can be used to decouple the top plate from the ceiling joists to allow 'flex'. Understand, the top plate must be secured to 'something' or the wall will have no structural integrity.

Take everything I say with a grain of salt Ask why this is such. I am with you, everything I have ever read about framing says attach the walls to the joists. I suspect the load bearing walls are attached directly to the joists, right? Why would you want the floors to flex? Seems like a flexing floor would lead to cracked tiles or gaps in the hardwood floors above. I guess there may be extreme situation such as earthquake zones, extreme temperatures, etc that may play a role in the local code.

Again take with a grain of salt. I've never heard of needing the floor above to flex. I've heard of needing to build in flexibility for the the cement floor to raise and lower (Colorado).

Are you sure you understood him right?

good diagram here:

http://www.asktooltalk.com/home/qand...ting-walls.htm

If they're in your budget, go with the DC04's.

I suppose you could build the wall 1" shorter than the ceiling, drill a 1/2" through the top plate every 4' and secure the top plate to the ceiling joists with a 3/8" lag bolt, leaving the 1" space between the top plate and ceiling joists. That would allow the lag bolts to drop down when the floor "flexed".

That being said, I have never heard about floors needing to "flex". I think it would be easier to build a load bearing wall to support the joists. Less bounce upstairs is a good thing, right?

I could maybe see an issue if you were building a wall out of 2x2's, the weight of the floor would flex them. However, I don't think it would be a violation.

Ask them if they are using the international building codes. I could probably give you more help if they are.

Wierd.

Tim

Where I live there is a similar requirement that top plates for basement walls must not be in direct contact with the joists above. Though for us it's more of a best building practice rather than actual code. They even give a guideline that there should be approximately 3/4" between the top plate and joists. Notice however that I said "directly in contact", of course you have to secure them to the joists or as Dennis pointed out you will lose a lot of structural integrity.

What I did was to measure all the joists, find the lowest one (my basement floor is horribly uneven), subtract 3/4" and build the wall as you normally would. Then I pre drilled holes between the top plate and joist (make sure to attach the bottom plate first and level the wall) and fastened with heavy gauge 4" common nails leaving the nail stick out beneath the top plate roughly the same as the gap above to allow the wall to move up and down while the nail remains in place. I did this at approximately every third joist and it is stronger than I could have imagined. If you're really concerned do it at every other or even every joist if no studs fall in the way of course. (Hope my crude drawing makes sense).

Or you can use RSIC-DC04 clips as you plan on doing. With nails it was easier and WAY cheaper. But the proper way if you're concerned with sound transmission through walls would be using the RSIC-DC04 for the added isolation they provide.

As to the explanation why this is done I would ask for a new building planner My understanding is this gap is to allow the basement floor to "flex" up/down with the movement of the ground beneath the foundation without disturbing the joists and possibly lifting them off the foundation and causing all kinds of problems.

Eric

Mojo- now that you say that, it makes sense.

If you are in a seismic zone, the foundation would be built to withstand seismic activity, whereas the basement floor would not.


Tim

Not only for buildings in seismic areas. I have an old house, it has solid foundation walls (12" solid poured concrete) but probably just had a dirt floor at one time that has since been poured over with concrete, in some places as thin as a few inches only. On top of the problem of the basement floor heaving upwards there is also the concern of the house sinking a bit (settling really) around the floor effectively lowering the joists in relation to the basement floor. I would suspect that new houses addresses some of these issues but codes are codes, even if they were written 500 years ago

I looked at that asktooltalk link for the door rough-in info. Is that right?! They say for a 30" door to start with 32" than add 1.5+1 inches. That's like 34 1/2" for a 30" door. On prehung doors I see the jamb, which is about 9/16th's thick on either side but that's it. That leaves over an inch for shimming? Seem like a lot to me...

I guess it's best to get all the facts before rendering an opinion

On the positive side, it's great that they let you know /before/ you start construction, rather than after the wall is up. After it is up I don't know that I would make issue of it, but now that you know, it's not that big of a deal.

12" solid poured concrete! Holy moly. Again I guess settling all depends are the particular scenario. Like you said newer codes address these issues. You really can't tell how wide the footing is, if the contractor distrurbed the soil under the footing, if there's clay under the footing etc..

Sorry for rushing to give my opinion. I have my particular area's conditions engrained in my brain.

Could be good WAF. "Honey, the inspector says I have to use RSIC-DC04's. Buy generic at the grocery store this week"

"He also said we needed 7.1 surround. Something about distributing the vibrations uniformly throughout the walls"



Tim

andy: I make my R.O. for a 30" door 32", assuming 3/4" jambs. Of course I make sure all my framing is plumb, because there is not much room to wiggle. I secure the hinge side directly to the framing and shim the latch side. If you don't own a 6' level, go 32.5" wide. Also make sure you don't have some wierd jamb stock.

wburtis: The 2000 I-code is basically what I use. It's a great (imho) document. I will take a look, but I don't remember ever seeing anying in the residential code. If you can spare the dough, it's worth picking up. Everything you need to build a residence in one book.

However, I would say it's definiely easier to build and stand up with 2x4's rather than build in place (assuming you are leaving a gap, if you want it tight, you're going to have to build in place). If you are using metal studs I would attach the top plate and build in place.

Tim

Tim, Yeah that sounds better. In fact that is what I used so now I feel validated.

wburtis, I used DC04's to attach my walls to the joist above. I also have a staggered stud wall. I spaced the clips approx every 48" and attached them to the top plate with the rubber end attached to the joist . Feels pretty solid to me.

Yeah, I installed them opposite to your photo. I've got wooden I-beams for the main floor floor joists. Turning the clips "upside down" was a better way for me to attach them to the joists. I don't think it matters which way the clip is orientated as long as it is attached securely.

I don't have a close-up picture but this pic might show it good enough. If not let me know and I'll take a close-up.

FYI, you can download an electronic copy of the 2000 International Residential Code for free here:

http://support.broderbund.com/faq_li...0050#downloads

Guy

I'm in the planning stages of my basement home theater near Denver, Colorado and have this same issue. The codes here require the floating floor joist to compensate for expansive clays that could push up the basement floor and damage the house structure.

I don't have a problem building it like the picture in the link above, but one answer I haven't been able to find on this forum is HOW do you seal this floating joist for acoustics? Would I just stuff insulation in the space below the wall? I'm looking at doing at least stagger-studded walls, but would this be pointless because of acoustic losses from this floating joist?

Are there any other HT owners/builders who have dealt with this problem?

thanks

Hi Black Banshee,

I'm in the Denver area as well, and there are a few of us around. I don't have the concrete basement floor, so I don't know what you can do for isolation here. You can use double drywall for sure, but I'm not sure how much it would really help if sound could just escape out around the moulding and all. I think stuffing with insulation here is probably ok if you can do it after inspection. Just my two cents,

-Ryan

if anyone tells you a floor needs to flex, i would not let them build anything for me. and yes you can get a "national" or even "state" copy of building codes, but the local county has the final say and over rules everything else.

Scott,

Check out pages 3 (item B2) and 11 of this PDF:

http://www.ci.broomfield.co.us/core/...s/bsmtfn04.pdf

This is how folks with concrete slab basement floors have to build walls in the state of Colorado to accommodate the expansive soils we see here. That's what is being referred to here. I believe the question asked is about the gap shown in the diagram on page 11 - how might sound isolation techniques be applied in this type of wall construction?

-Ryan

holy cow............i stand corrected (and blushing). i have never heard of such a thing. i guess i need to get out of indiana once and awhile!!

so how do you all measure for "uplift" to figure how short to leave a wall from the floor joists?
i also thought he was saying that the upstairs floor needed to flex.

Hey Ryan - great to know there are other Colorado HT builders! Just read through your construction thread, I'll be watching intently, looks like fun. My house is currently under construction and will be done in late April. Like you I've been lurking on AVS for over a year taking notes and making plans, I hope to get started in May/June and "try" to get it done by the end of 2007 (yah right).

I researched doing the floating floor like you. My builder over-excavated the site down to 30 feet and then replaced the soil. Also the soils report says that my site has supposedly "low" risk of clay expansion. Based on this over-excavation, only about 5% of the people in our development decided to do the floating floor (not to mention the builder wanted $17,000 prior to starting build before they'd do the floating floor). Did your builder do the over-excavation? Did you have a higher risk of clay expansion? Just curious what drove you to the floating floor. Thanks for the link to the Broomfield basement checklist, I'll check around for something similar in my county. Save me a seat too for opening night! I'll do the same.

For my home theater, I intend to go with full-blown acoustic treatments (double 5/8" drywall, Green Glue, solid core doors, floor-mat, linacoustic on the walls, soffits, bass traps, sand stage, etc). BUT, I'll be very frustrated if all this work is meaningless because of acoustic losses through the floating floor joist. I'm planning to visit a pro-installer in the area (maybe ListenUp?) and get some pro advice. I'm sure I'm not the first to address this question.

To ALL: is there anyone else on AVS that has dealt with the floating floor joists and how to acoustically seal it? Better pic below.

Banshee, is your builder Meritage? I have Meritage in Parker, and they did the same thing (excavation). No floating floor for me, just a slab. No clue what to do about the wall though. Maybe insulation, and caulk around the base trim. I also thought you could still drywall all the way down. If there is expansion, the drywall will crush though.

I didn't mean to make you blush! I've lived out here for just over two years and have learned that some of the building stuff here in Colorado makes for some interesting challenges.

I have no idea what the distance is between the slab and the base of the wall, but rest assured that "hanging" these walls is a huge hassle and I'm really happy that my basement doesn't include a concrete slab. I see the next post says 2" minimum. The idea is that your drywall doesn't connect with the bottom plate and there's enough gap for your baseboard cover everything and work.

Hey, thanks for reading! Good luck on your project too. I'll be watching.


I totally got lucky in our case. I had wanted the floating floor, but didn't want to pay for it. The builder said I could have a slab floor and we contracted to build w/ that option. When they went to the city to permit, the city said based on the soils report that I could not have a slab floor and the builder had made mistake. So, they went ahead with the floating floor and I didn't have to pay the extra cost (I think it was around $8K.) There was no option for extra excavation though - just slab (if your lot's soils report allowed it) or floating floor. I'll be happy to have an opening night for anyone who'd like to come check it out when I'm done, and count me in for yours as well.


I don't know if the folks at ListenUp know this stuff, but it seems like a reasonable place to start. There are a number of other installers in the area but I have no idea what kind of expertise they have.

Good luck with your construction and your build. Take lots of pictures of the house as they build it now - it'll help you later.

-Ryan