Residential beam sizing for deflection 3

[Rigger12]

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.

 

[Rigger12]

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

 

[DoubleStud]

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.

 

[jerseyshore]

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.

 

[jayrod12]

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.

 

[skeletron]

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.

 

[milkshakelake]

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.

 

[Rigger12]

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.

 

[MetwoodBS]

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

 

[Eng16080]

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.

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.

 

[phamENG]

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...

 

[MetwoodBS]

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

 

[Eng16080]

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.

 

[DoubleStud]

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

 

[Eng16080]

That's a good point regarding camber.

 

[XR250]

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.

 

[phamENG]

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?

 

[MetwoodBS]

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

 

[XR250]

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?

 

[phamENG]

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.

 

[Eng16080]

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.