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Residential beam sizing for deflection
3

Residential beam sizing for deflection

Residential beam sizing for deflection

(OP)
I'm currently sizing a beam to take out a load bearing wall in my own home (to open up between the kitchen and dining room) and have a couple questions about how you size for deflection limits when removing an existing wall, on new construction we size for live load deflection as the dead load deflection wont effect the finishes, but since this is a finished structure should I size the beam to deflection from the combined load, otherwise when we put up the beam and remove the supports the beam will deflect and the upper floor will settle from the dead load deflection and could mess up some finishes or the levelness of the floor above. The span is 16'-6", and it will support a bathroom on one side with a 14' joist span and a bedroom on the other with a 12' joist span, so the tributary width is 7' from the bathroom and 6' from the bedroom, also there is a partition wall that is not load bearing above the existing load bearing wall.

I am getting a live load of 460plf and a total load (live + dead of) 745plf with everything considered (40psf LL bathroom, 30psf LL bedroom, 15psf deadload both in case we ever switch to porcelain wood look tile in the bedroom, plus a few other loads we have), I'm winding up with a 14" or 16" in parallam beam, which I likely won't do because it's 2x8 framing on the floors and we don't want the beam sticking down that far. The limiting factor is deflection limits, not moment or shear. So the question become because it's a long span with tile above in the bathroom do I use L/480 or L/600, and do I use live load deflection or total deflection, L/480=.415" L/600=.33 inches, I'm worried if I size for live load when we remove the supports any settling will disturb the floor above.

Am I being grossly over conservative by sizing for L/600 for total load deflection. Since it's my own home I don't want any chance of the floor bouncing or settling, the house was already built cheap by the builder in the 80's and I'm been improving everything in it as I've been living there.

It seems no matter what I'll have a little of a bump down in the ceiling where the beam is as it's only 8" framing and I'll have to go with a W8 of some weight. I don't mind sizing it a size up as I will be supplying and furnishing the steel myself, just curious for any input as I don't really do any residential work.

RE: Residential beam sizing for deflection

I've commonly heard it said, that the structure neither knows nor cares if it's residential, commerical, industrial or other!

Yes! It's YOUR home! Be satisfied in the end!

I would design for LL Deflection of L/600!

If you need to bump down, you could add pseudo wood or drywall/plaster beams at equal spacing per your preference!

Are you intending on the joists to be top bearing?

Would your floor plan allow for (2) shallower beams with cantilevered joists?

At 16', deflection will TYPICALLY control! But, with half the loads, perhaps you can brainstorm with options!

It looks like a simple matter of aesthetics with limited depth!

RE: Residential beam sizing for deflection

I have a slightly longer, similar span with 2x8's in my kitchen and went with a W12 + 2x nailer. Creates a nice little visual separation between the spaces.

Going with a W8 in 2x8 framing is going to show a weird 1-3" bump in the ceiling. That will look like crap. Anything less than 4-6" is going to look awkward.

My advice is to size a W10 or W12 with a 2x top flange nailer. You'll save money on the steel (plus it's lighter to pick up), you'll hit L/480 deflection easily (L/600 probably going up one or two sizes), and you'll have a normal little bump of sheetrock in the ceiling.

RE: Residential beam sizing for deflection

(OP)
We're looking to cut the existing joists, pack the beam with hardwood and put the beam up in the floor and then attach the joists with hangers, that way it will be as little hanging down as possible, we only have 8' ceiling and were trying to not have any bump down, but 2x8's are only 7.25" deep, the W8 will be between 8-8.25" deep. I figure I'll just upsize it one size from the size that satisfies L/600 for LL and that'll give me about L/600 for combined and I won't have any worries, for the little price difference and the beam only being 1/8" deeper.

Not really seeing any way to make it so the ceiling could be completely flat, it'll have to be about an inch deeper where the beam is, maybe we'll just put up one of those fake wood beams that are hollow over it to dress it up a little.

We're going to supply and install the steel, and I'm working with a carpenter/home builder/ general contractor we've done a lot of work with who will be doing the rest of the buildout like the connections of the joists and the finishes, so I've been getting a bit of an education in wood framing as I've never done anything related to wood before other than my studying for the PE exam.

RE: Residential beam sizing for deflection

The only way to make a flat ceiling with 2x8's is a heavy flitch beam with 7.25" LVL's.

Like I said I have the same exact setup as you 8' ceiling and all. Losing 6" to the ceiling is negligible. A W8 top flush sticking down 3/4" will look awful. If you are going to do a fake wood beam overtop then you are better off utilizing that height with a W10 or W12.

Also I always recommend adding a top flange nailer. Plywood right on a steel beam is a squeaky setup. You'll be cursing yourself forever if the floor squeaks upstairs everytime you walk over the beam.

RE: Residential beam sizing for deflection

(OP)
Thanks for the info, I'll talk to my GC to see how he would want to do that. I also just looked into doing (2) MC7x22.7's back to back, I'm getting a LL deflection of L/709, and total deflection of L/438. So that may also be a winner since it's only 7 inches deep. My main concern is the total deflection as now there is probably negligible deflection of the floor above since it bears on a wall, with the MC section I will probably see about 3/16" deflection due to dead load, then the LL deflection could be up to almost 1/4" for a total deflection of .452".

I also see a local steel supplier sells what they call a "Super 7" steel beam that's 7 1/8" deep to fit in a 2x8 framed floor, they say it's "structurally equivalent" (in what way I don't know) to a W8x31, and their span & load charts specifies it for my load and span case, but I probably have to call them for more information as they give no information for deflection or structural properties so you could run calculation. It looks like a W6 with plate welded top and bottom.

RE: Residential beam sizing for deflection

You could do a big W8 and cut out the floor sheathing to make it totally flush. No way a flitch is working if dbl. MC7x22.7 is the ballpark.

RE: Residential beam sizing for deflection

L/600 for beams and L/480 for joists (both total load) is my standard for custom homes. The alternative is doing an actual vibration analysis, which can be a bit of a pain (though I did set up a spreadsheet to do it for simply supported beams).

I just renovated my already enclosed garage to split it into a couple of rooms. We had a similar situation...triple 2x12 girder with 2x10 joists, so 2" hanging down. Looks terrible. We wanted a flat ceiling in the new room, so I furred the ceiling down 2.5". Not really noticeable (a 2 car garage with 8' ceilings has terrible proportions anyway), and the room still feels normal even though I'm taller than average. So that could be an option - get as shallow as you reasonably can, and then lose a couple of inches throughout.

RE: Residential beam sizing for deflection

Quote (jerseyshore)

Also I always recommend adding a top flange nailer. Plywood right on a steel beam is a squeaky setup. You'll be cursing yourself forever if the floor squeaks upstairs everytime you walk over the beam.
So you are suggesting to add a nailer, but nothing will be nailed to it? Interesting. How about adding glue to top of flange? Tape?

I think with 2x8 floor framing you are out of luck. IMO using W10 and let it sticks out below the ceiling is your best bet (wrapped to make it look like heavy timber). I am not sure flitch beam with LVL will do much with only 7.25 deep. Plus more than likely this beam will probably run parallel to a wall that is only 2X6? 3-lvl with two 1/2" plate is already at 6.25" wide. We probably dont want to be that much wider than the 2x6 wall?

RE: Residential beam sizing for deflection

Regarding the nailer - as long as you keep the beam down 1/8" to 1/4" from the floor sheathing, you'll be fine without it if you're using packing and face hangers. That way you don't have contact between the plywood and the steel, if there's any shrinkage/settling of the framing into the hangers you won't get a high spot. Shrinkage is unlikely as they are existing and EMC is stable, but settling will happen if they aren't seated just so.

RE: Residential beam sizing for deflection

A W8x24 is similar I to dbl MC7x22.7.

RE: Residential beam sizing for deflection

(OP)
Pharmeng yes, sadly the double MC7x22.7 is L/438 in deflection from total load, I was trying to keep it under L/600 total, I’m not looking at the numbers now but I think I would need an W8x40 to keep it to L/600 total, which would stick down from the ceiling a little bit.

XR250, the advantage of the MC7 would be that it would only be 7” deep, going to a W8 makes it 8” deep

RE: Residential beam sizing for deflection

You can cut the subfloor and let it flush out on top. Done frequently around here to use 10" I-beams in 2x10 floor systems.
The fact is the beam will be lucky to ever see 20% of the design load so you could back off L/600 TL.
I usually use L/600 LL
Also, I have not done the math but something does not seem right about needing a W8x40 for a 16'-6" span.
I have a job now where I am using a W8x48 on a 20 ft. span with alot more load.

RE: Residential beam sizing for deflection

Messing around with the subfloor above or holding down a beam a small amount is not something I've ever seen done nor something I think I'd ever consider. If I'm that tight on space and it has to be flush they can just put the beam right under the plywood. Don't want a squishy spot above.

DS, to answer your question, a nailer is obviously better when the subfloor gets nailed to it above, but if it's just a first floor reno, I still specify the same unless they really need that inch back.

A nice piece of wood between the top flange and the plywood above not only gives you less squeak potential, but it also allows for a little adjustability on the total height of the system. Can always shave it down or build it up to line things up. These homeowners aren't getting the top of the line steel contractors putting up their living room beams.

I also agree with XR that with bedrooms above you'll never see half of that design load. Reality is anything over a W8x10 will probably barely deflect at all.

RE: Residential beam sizing for deflection

(OP)
So that comes back to my original question of if I was being grossly over conservative trying to keep total deflection under L/600, which some seem to be saying I am others are saying that’s what they design to.

The double MC7x22.7 would satisfy a live load deflection of L/600 (would be L/709), but it would only be L/438 for total load, but the benefit would be it would easily fit within the floor.

You’re right it would likely never see the full load since it’s a bedroom on one side and master bath on the other, and the tub and shower are on the other side of the joist span right next to the exterior load bearing wall, so it won’t take much load ever from that end either. I’m definitely just overthinking this because it’s my own house and I have to live with it.

I attached a rough current floor plan and a floor plan we’re considering just for the sake of it, the beam would go where the current wall is between the kitchen and dining room that the desk, oven and refrigerator is currently against, there is a void behind the desk where currently is the air return to the AC air handler in the basement. The beam would span from the wall where the stairs are on the left end of the dining room to the wall on the right side of the dining room where the oven currently is.



RE: Residential beam sizing for deflection

Here is one I looked at the other day. They screwed this one up though as they used a 10 1/2" tall W10x30 I am not sure how the flooring will work out!
I usually only do this with a W10x33 as it is 9 3/4" which gives me a little wiggle room.


RE: Residential beam sizing for deflection

I believe the various tile floor associations have recommended floor deflection limits dependent on the type of tile. You might want to look into that.

I would try to center the double MC7 beam on mid-depth of the 2x8 floor joists with there being small gaps both top and bottom to accommodate some movement of the wood without creating a noticeable bump at the steel beam. The joists are probably close to 7 1/8" deep if I had to guess (due to the wood drying/shrinking after construction).

I've seen the detail above before, with the floor sheathing cut and the beam flange flush with the top of sheathing. I would try to avoid that if possible.

This is slightly off topic, but I can never understand why having a flush/hidden beam is always so important to people, with the exception of there being an actual head height issue. It seems that this is a major concern of clients/owners on about half of projects. In the end, they end up with a vast, unbroken plane of ceiling spanning like 30 or 40 feet with no visual interest. If the drywall job isn't perfect, it's really noticeable over such a length. My ideal aesthetic would be something along the lines of the beam sticking down 6 or 8 inches, which would coincide nicely with a steel beam deep enough to likely limit deflection to 1/8" or so. This is of course subjective and just my opinion.

RE: Residential beam sizing for deflection

a few thoughts:
  1. -sometimes its better to go with an absolute number for deflection. Keep the dl defl low because these will be actual cracks in your existing drywall upstairs. LL deflection can be a reflection of the existing stiffness of your house.
  2. -be mindful of the location of the posts. I think its' better if the posts miss the existing footings because then you don't have to justify the additional load on the existing...you just install a new footing. Hiding them in the wall like you show makes it much more difficult.
  3. -You may want to stiffen the floor in the new big space while you're at it.
  4. another idea: could you put an 18" lvl in the attic and hang your beam from that?
  5. -You didn't ask, but in my opinion a big room with a low ceiling is out of proportion and an 'open concept' kitchen/dining is not necessarily the improvement people hope for. An alternative would be making a wider cased opening that has better lines of sight from one space to the next and lets you use your dining room for eating instead of the new giant piece of stone counter

RE: Residential beam sizing for deflection

Playing off of kipfoot's recommendations for considering shortening the opening, I've had success in convincing homeowners to put a post at the end of their island to cut the beam spans in half. I then tell them to add some electrical outlets and maybe the light switches for the island lights etc to this post. Everyone always wants to charge their phones, use small appliances etc while at the island. And a single post really doesn't obstruct the view.

Just a thought to consider....

Something that hasn't been discussed, be mindful of what this will do to your main floor beam. Depending where your posts supporting that are, you may be significantly reducing load on one span, and significantly increasing it on the adjacent one. You may end up with some issues with that beam. In my experience those beams usually have a bunch of electrical or plumbing attached to the sides, or ducting running directly adjacent, making reinforcing of the existing beam difficult. Putting a post at the end of the island may solve that by keeping the similar total load values in the same beam spans.

RE: Residential beam sizing for deflection

kipfoot brings up a good point.

While the outward features of Palladianism have certainly faded (when was the last time you saw a symmetrical house with ordered columns and dome?), there are still quite a few architects out there that lean on his ideas of proportions to plan rooms that are comfortable and pleasing. The large room you're creating with the kitchen and dining room are actually quite close to one of his favored plan proportions - the square and its diagonal (1:1.414, you have 1:1.443), but the plan dimensions are not the only important feature. You also have to look at ceiling height. He used 3 calculations to determine that: the arithmetic, geometric, and harmonic means. For all three of those, this room wants about a 19 foot ceiling height. Now, that's a bit extreme, and not entirely necessary if you'll have, say, pendant lights over the counter to help split the space. But I wouldn't want this room with anything shorter than 10ft ceilings for sure, preferably 12ft.

RE: Residential beam sizing for deflection

(OP)
Thanks for the suggestions, yeah so maybe it would make sense to just go with a W10 and clad it to look like a reclaimed wood beam to break the ceiling up, and I appreciate the other suggestions to, I’ll have to give those ideas to my boss (my wife), she’s the one that ultimately has to like it and I just have to make it work lol. Architecture and interior design certainly isn’t my specialty, we’re going to check out a could design places and try to come up with some ideas, the one layout is just something I threw together quick based on her ideas

RE: Residential beam sizing for deflection

Rigger, sorry I didnt read the whole responses. You can reduce the span of the beam by really thinking about where to put the fridge because you can put a wall behind or next to the fridge. If you put the fridge against that wall you are removing, you can keep the wall behind the fridge and reduce the span. If you put it next to the stairs, you can maybe leave a wall the same depth as the fridge and it will reduce the span a little bit.

RE: Residential beam sizing for deflection

I agree with kipfoot and that's similar to what I said above, a visual separation between spaces is good for lower 8' ceilings. If the beam was going to be randomly across the kitchen in an awkward spot, getting it flush would be more important. The beam between my kitchen and LR is right above the edge of the island where the seats are and it looks fine.

But adding a post on an island stinks. Unless the span is something absurd like 30 ft+, get a bigger beam. No one wants columns at their island. Put the outlets in the sides of the island like everyone else.

RE: Residential beam sizing for deflection

Quote (jerseyshore)

But adding a post on an island stinks. Unless the span is something absurd like 30 ft+, get a bigger beam. No one wants columns at their island. Put the outlets in the sides of the island like everyone else.
I agree no post is preferable, however when it triggers weird condition, or upgrades to the main floor beam that would be near impossible to complete given the likelihood of HVAC and electrical in the way, it is often necessary. I can't recount the number of times it's been a successful sell to many homeowners that are looking to create as much open space as possible on the cheap. Not to mention it would facilitate a far shallower beam supporting the second floor.

RE: Residential beam sizing for deflection

My approach with residential beam sizing:
1. Check the existing deflection and try to match, or get within an increase that is not noticeable (1/8" or so).
2. Use L/480 minimum for live load deflection. I also tend to focus more on the total load deflection, which is a bit conservative.
3. Being aware of brittle finishes (bathroom tiles, flooring, etc.) and bumping the deflection limit up to accommodate.
4. Sharpening the pencil with loads especially if #3 is true.
5. If the span necessitates a steel beam, I almost always kick it up a couple sections and base my decision on flange width, beam depth and how that affects the floor. In my opinion, if the Client is doing a big enough reno that necessitates steel the added steel weight is a non-issue vs. having a good performing floor.

The other thing to consider is that, in many insurer's eyes, beam deflection is not a "major structural defect" if it meets the minimum code requirements (L/360, L/240, L/180, etc.). I know this isn't a good rationale to hang your hat on in terms of design, but keep that in mind to help you sleep a bit better at night.

RE: Residential beam sizing for deflection

For my own house, I just went all out and oversized everything. Zero issues. I have a contractor friend who did that too, installed some oversized steel. The price differential from the smaller/cheaper materials wasn't as much as I'd expected.

I've seen enough deflection and serviceability issues in my life that I don't want it happening in my own house. I decided to live with a few soffits and dropped beams. I strategically framed around posts and I still have a decently open layout. It's not perfect, but it's structurally good.

RE: Residential beam sizing for deflection

(OP)
That’s exactly what I’m going to do at this point, I wasn’t sure if I was being drastically overconservative with the deflection limits I was trying to meet, and from the different opinions it doesn’t seem like I am, I was trying to fully hide the beam in the ceiling, but I’d rather just upsize it a little and be positive I’ll have no issues.

It’s my own house, I’m sizing the beam, I’m field measuring and fabricating it in my shop, and my crew of ironworkers will install the steel (again overkill for residential work lol), if there was any issue it’d be 100% on me and I’d have to live with it. I’ll just go with a W10 or W12 that I know will have almost zero deflection issues and clad it to look like a wood beam and never have to worry about it.

RE: Residential beam sizing for deflection

We might be able to manufacture a beam that is 7 1/4 depth. I ran some preliminary numbers and it does work. We just need to get some additional information. I read your post and not all the others since this thread was several days old. visit Metwood.com and check out our TUFFBEAM product





Metwood.com

RE: Residential beam sizing for deflection

Quote (Rigger12)

I’ll just go with a W10 or W12 that I know will have almost zero deflection issues and clad it to look like a wood beam and never have to worry about it
This is the way! Exactly what I would do if this was my house.

Quote (MetwoodBS)

We might be able to manufacture a beam that is 7 1/4 depth. I ran some preliminary numbers and it does work.
What are the section properties for this beam to get it to work based on the above requirements? Based on the load chart from your website, it doesn't look like a 7 1/4" deep beam will work. I'm also curious how you would support wood joists in a flush mount condition.

RE: Residential beam sizing for deflection

TUFFBEAM! That's it. I was trying to remember your product a while back but couldn't. My former boss used one in his house - he was impressed with the performance and ease of installation (he self performed - his father was a GC and he spent his formative years erecting metal building systems before becoming an SE). Couldn't remember what it was called, though. Filing that one away for future use...

RE: Residential beam sizing for deflection

We would have to use a three or 4 ply to get 7 1/4 to work. However, I have the ability to camber our beams to help with deflection.

The joist hangers would fasten to the side of our beam with self drilling screws or we can add wood to the side so the hangers can be nailed on. Keep in mind, if you need a hole for passage, I can put up to a 4" hole anywhere along the beam you need it.

I prefer the direct to the side with self drilling screws.

Metwood.com

RE: Residential beam sizing for deflection

MetwoodBS, Thanks for the follow-up. I'll have to keep this in mind in case I need such a beam in the future.

Btw, on the website, the PDF link on the left didn't work for me when I tried to download. I assume it contains dimensions and material properties.

RE: Residential beam sizing for deflection

Wouldn't it be hard to install if you camber it for this application? Probably better for new construction?

RE: Residential beam sizing for deflection

That's a good point regarding camber.

RE: Residential beam sizing for deflection

I like this light-gage option. My concern is availability locally in a timely manner.
Also, if web stiffeners are needed, it is another thing for framers to overlook.

RE: Residential beam sizing for deflection

XR - not much availability problem for us. They're located in Roanoke. I know of at least one installation here in Hampton Roads.

MetwoodBS - what does your distribution network look like? Are you mostly special order, or are you stocked in building supply warehouses?

RE: Residential beam sizing for deflection

We ship product across the country. Everything is fabricated in Virginia. We now have the ability to build our beams to be field trimmable up to 2' feet. We have a discounted rate for shipping with T-Force through a members discount program by being members of the National Association of Home Builders.

Doublestud questioned about installing with camber - It works best for new construction because of the time and loading being added over time. However, Camber in some instances can help remove the bounce and in most cases doesnt need to be more than 1/4 or 1/2.

XR250 - Web Stiffeners are already installed when we fabricate our beams. That eliminates the possibility of a framer forgetting to add.

Metwood.com

RE: Residential beam sizing for deflection

Quote (MetwoodBS)

We ship product across the country.

I'm in the triangle region of NC. If I was to try to replace, say, a W8x18 with one of these (based on stiffness), what would be the approx material and shipping cost?
Trying to gage the relative costs.

"However, Camber in some instances can help remove the bounce "

How does this work?

RE: Residential beam sizing for deflection

I'm curious - do you have any 3rd party testing reports for your products? As Eng16080 mentioned, you have a broken link on your website. Maybe that's it?

Many (perhaps most) engineers won't specify a manufactured product like that without some sort of third party testing being done to verify that the performance matches the analysis, and there are quite a few jurisdictions that won't accept it without a similar certification.

RE: Residential beam sizing for deflection

Quote (phamENG)

Many (perhaps most) engineers won't specify a manufactured product like that without some sort of third party testing being done to verify that the performance matches the analysis, and there are quite a few jurisdictions that won't accept it without a similar certification.
I'll admit to generally being hesitant to spec 3rd party products. Often the marketing material will make bold claims overstating what the product can do, which you only realize after spending hours reading the fine print or some evaluation report. I've been burned on this enough times that I'm now naturally hesitant.

Regardless, with all the high end residences being constructed nowadays, it seems there could be a market for a high-strength steel beam with depths matching (or close to) typical wood floor framing. If a company could roll steel I-beams at 7 1/4", 9 1/4", and 11 1/4" depths, I can see demand for that. Perhaps they could even ship the beams with the webs packed out with wood nailers. It would be nice if AISC had standard I-beam sections in these depths. I've used back to back MC7s before to fit within 2x8 framing, and everybody loved that solution.

Perhaps TUFFBEAM is what we're all looking for, but I think most of us will be hesitant initially.

RE: Residential beam sizing for deflection

"MetwoodBS". - might want to change your handle!

RE: Residential beam sizing for deflection

Quote (Eng16080)

I'll admit to generally being hesitant to spec 3rd party products. Often the marketing material will make bold claims overstating what the product can do, which you only realize after spending hours reading the fine print or some evaluation report. I've been burned on this enough times that I'm now naturally hesitant.

Same here. Also, frequently when they send me the calcs on the product, I find too many liberties taken or issues not addressed

RE: Residential beam sizing for deflection

We have performed testing at Intertek and NTA. We provide engineered "Beam Sheets" with each one of our products and it is sealed by a licensed engineer. We have been fabricating our joist and beams for more than 25 years.

We roll our Cold Formed Steel products 7 1/4, 9 1/4, 12, 14, 16 to match several of the wood depths. I can get 11 1/4 also, but more residential customers are using 11 7/8 versus 2x12.

I know we have some issues on our website that are not working properly. I apologize for the inconvenience. We have been building a new site and will be launching within the next week.

We are in the process of working with the Home Innovation Research center and IAPMO to achieve a Code Compliance Research Report.

If you have a sample loading or a beam in mind, feel free to send me an email at scallahan@metwood.com and I can send you over a sample beam sheet. I know XR250 asked about a W8x18. I can build a beam in 7 1/4 depth or 9 1/4 depth and the price varies based on stiffness requirement.

I have attached a copy of a Beam comparison between on of our 14" Beams and a triple 24" lvl.

Metwood.com

RE: Residential beam sizing for deflection

Quote (Metwood BS)

I know XR250 asked about a W8x18. I can build a beam in 7 1/4 depth or 9 1/4 depth and the price varies based on stiffness requirement.

W8x18 I = 62. Price + shipping for the 9 1/4" Equiv.

RE: Residential beam sizing for deflection

Metwood, Thanks for all the information. What are the general material properties of the beam? I see it's light gauge. Is it using 50 ksi steel (yield strength)? Is the steel being rolled into tube sections which are then welded closed (like an HSS)?

In the interest of this particular thread and OPs original question, would you be willing to provide a calculation for a 16'-6" span beam with DL=195 plf and LL=460 plf?

RE: Residential beam sizing for deflection

The beams appear to be "C" sections. How are the ply's connected together to transfer unequal loading shear?

RE: Residential beam sizing for deflection

Eng16080 Do you have a requirement for LL Deflection? Is their a Height Restriction? I can do the beam in 9 1/4 I went ahead and attached a 9 1/4"sample and a 12" sample.

XR250 and ENG16080 - We use Cold Formed Steel C-Studs that are 50 ksi steel and weld A706 reinforcing steel to the corners of the web and flanges to add additional strength. We weld two Studs together at the flanges to create a box beam. We change bar sizes based on loading and deflection criteria. In the attached example the 9 1/4 beam contains internal #9 bars and the next post the sample 12" beam contains #6 internally. We can also add additional plys if necessary due to height issues.

We place a rebar grid at the ends to handle shear and allow the beams to be trimmed in the field up to 12" off each end.

For the example for Eng16080 - I could fabricate a beam that is 18' with one or both ends trimmable so the product is on site while they are framing. I can also cut to length. However, things sometimes vary and having it too long is better than to short.

Metwood.com

RE: Residential beam sizing for deflection

MetwoodBS, I meant for the beam to be 7 1/4" deep to match OPs floor depth with deflection criteria to also meet what's indicated in the first post (if that's possible). But what you sent should be sufficient for us to get a better idea of this product. I'm not intending to make you do a million calculations here.

RE: Residential beam sizing for deflection

Quote (MetwoodBS)

We weld two Studs together at the flanges to create a box beam.
So if they are welded together in the factory they are ultimately going to be heavier than the red iron I-beam equivalent due to its shape being more efficient.
So where does the economy lie?
Still looking for a W8x18 equivalent to compare.
An 800S200-97 has an I of 11.2 and weights 4.3 plf - so need say 6 of them for equivalency to a W8x18.
The weight would be 26 PLF and it would be 12" wide. I do not see how this is practical or saving money.

RE: Residential beam sizing for deflection

XR250
My 7.25" x 5" beam to carry the load is 19.9 lbs a foot
My 9.25" x 5" Beam to carry the load is 20.9 lbs a foot
If you have the room, my 12" beam is only 14.7 lbs a foot.

The difference is the connections. All connections to my product are made with self-drilling screws. To connect to a W beam you either have to use Powder Actuated Fasteners or Bolts, which require a lot of labor. If a w beam is flush, then you are required to add several lays of wood that has to be ripped to the correct size and then through bolted to the web.

If you just compare cost, I may not be as inexpensive as a W8x18. However, if you need to attach or cut to length, then the labor cost is much less. We have framing contractor request our product over W beams and Engineered wood so they don't have to build them onsite.

Metwood.com

RE: Residential beam sizing for deflection

MetwoodBS, Thanks for the calculations. A few quick questions:
  1. "Deck Connection: Nailed". Are special nails required to fasten to the LGS?
  2. "Design assumes continuous lateral bracing for both flanges." Is this the case even if the beam is simply-supported? I would expect only top flange bracing needed in that case.
  3. "Web stiffeners are required at all bearing and point load locations unless reviewed by a design engineer." You mentioned that the beam would be supplied with web stiffeners, or am I missing something?
    As you mentioned above, I'd be worried that this would get missed in the field if not supplied with the beam.
  4. It's perhaps irrelevant, but the software output is a bit confusing in listing the Live and Dead loads as 40 plf and 15 plf. I think it should read as "psf" instead.

RE: Residential beam sizing for deflection

I think you answered my question #1 above. I assume deck is to be attached with screws, not nails.

RE: Residential beam sizing for deflection

Choosing my words carefully, if anyone intends to use a product manufactured by Metwood, or a similar manufacturer that does not provide an ICC-ES code evaluation report, I would strongly suggest characterizing the product as a deferred submittal item, and requiring sealed analysis of the product prior to including it on your designed plan set. I have no experience with the TuffBeam product, so I am unable to speak to it, however, some of the repair options provided by Metwood appear to play a little fast and loose, and if I was asked to review it by a GC, I would expect evidence submitted as well as a sealed set indicating adequacy of the repair solution for each specific design condition, similar to truss repairs.

RE: Residential beam sizing for deflection

Do people normally approve products without ICC reports? No ICC report is a no-go for me. In NJ the building officials don't know anything about structure, but one thing they do ask for is code approvals on specialty or not-so-popular products.

RE: Residential beam sizing for deflection

Quote (MetwoodBS)

7.25" x 5" beam to carry the load is 19.9 lbs a foot
I find it hard to believe this is equiv. to a W8x18. Can you show me some section properties?

As far as attachment goes, many times contractors just notch the joists into the web of the W8 and then block between so no fabrication is required.
I only see these useful for use floor systems or ridges where things need to be totally flush. For most ridges and garage door headers or other situations, taller LVL's work fine and are much cheaper and easier.

RE: Residential beam sizing for deflection

Quote (jerseyshore)

Do people normally approve products without ICC reports? No ICC report is a no-go for me. In NJ the building officials don't know anything about structure, but one thing they do ask for is code approvals on specialty or not-so-popular products.

Samey sames, jerseyshore. I'm in north jersey, and I wouldn't spec a product that didn't have an ESR report unless I was designing it myself, or it came with a calc package with a raised seal. I don't want that liability.

RE: Residential beam sizing for deflection

I just recently had a building official (one of the Amboys or Woodbridge I think) ask the contractor to bring a box of unopened carbon fiber straps along with my letter/ drawing to prove to them what product they were using on-site. It's literally the only time building officials give a shit about structure in NJ. I even had a building official call me to ask if an architect can size a steel beam or if it needs to be an engineer lol. Would be a fight to get something like this thing approved that's for sure.

RE: Residential beam sizing for deflection

(OP)
Looking at the numbers provided in Metwoods example for the 7 1/4" beam for my situation, I dont see how it's better than a double MC 7x22.7, I have a 13' triburaty width, LL 40psf, floor DL of 15pf and I added an additional linear deadload laong the beam for a partition wall located above the beam location, so I have a Live Load of 520plf and total load of 790pfl, with the MC 7x22.6 I get LL deflection of 0.3144" which is L/627, Total deflection is 0.4792" which is L/413, like I said I was attempting to keep total deflection under L/600 if reasonable, with a W10 or W12 it is.

The Tuffbeam example given is showing LL Deflection of .5292" and Total Deflection of .7764", even with a 1/4" camber I don't see it outperforming the MC7x22.7 based on these numbers.

RE: Residential beam sizing for deflection

Quote (Rigger12)

Looking at the numbers provided in Metwoods example for the 7 1/4" beam for my situation, I dont see how it's better than a double MC 7x22.7
It's definitely not. To be fair, I don't think MetwoodBS was necessarily making that claim.

In terms of pure strength within a confined depth of 7.25", you can't do much better than a double MC7x22.7, or at least that was my determination based on a prior project where I needed a very strong wind column concealed in a 2x8 wall. I suppose you could sandwich a steel plate between the two MCs to get extra capacity.

Not that this matters in your case. The W12 is the way to go, IMO.

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