40'x40' loft - I beam or H beam load/span? for 40' mezzanine design

The people on here seem to really know their stuff and the mathematic equations required to determine what I need. What I have is a 40x40x25' tall shop that has all this extra height we would like to take advantage of by build a loft that we could use as a large studio apartment / office. I would like to know what it would take material / beam wise and their sizes to make a 40' span down the center supporting the 20' cross members going out to each side of the building. I would consider adding a vertical support or 2 in the center if absolutely required and if it meant a drastic savings on materials and so forth. But to start I would like to try and estimate the project from the expensive end if we were to remain the free spanning downstairs. I was told according to the 2015 IRC for the live load we would need 50psf uniform and 1000psf concentrate with a floor deflection live load of L360, with downstairs being a garage with light manufacturing that is 150psf uniform and 2000psf concentrate. It asked about the collateral loads but I wasn't sure if that was a different term for any of the above info about code weights or not.

I wanted a downstairs height of 15', which would give us 2' of space to build the floor while still having 8' ceiling height at the eaves upstairs. Since we don't have any height restrictions to the floor thickness itself, instead of all the cross member beams meeting perpendicular with metal plates and bolts to the main support beams keeping them on the same plain. We had planned it would be easier to install if we ran 2 main beams north and south on either side of the shop and 1 down the center then stacking the cross beams running east and west on top of the first beans instead of connecting them to the side of each of main support beams and having to drill a 1000 holes with connecting plates. Then we had planned to weld each beam connection along with gussets on each joint to help with lateral loads. I should mention the 2 main beams running north and south 40' along outside walls do not need to be free spanning since they are along the walls any vertical supports required would be out of the way. The 3rd main beam running north and south down the center of the shop would be the only beam we prefer to span the actual 40'. This way the cross members running the opposite direction only need to span 20' instead. Then if absolutely necessary or if a major cost savings adding a vertical support or two down the center of the 40' beam in the middle of the shop. I had thought this might be cheaper by having 3 main beams where only 1 makes the actual 40' span instead of only 2 main beams down each outer wall while each cross member made the 40' span. I definitely need some engineering advice as to what the best design would be as well as the materials it will take to maintain the load requirements. The foundation itself is 6" thick fiber reinforced, while 18" around the perimeter the foundation drops down to 12" thick for the footing.

Even though the shop is a good size with some heavier equipment downstairs the upstairs would basically just be where I have some clean quiet space to do my upholstery work and may be an apartment type setup I could use with bathroom and small kitchen for use from time to time. So I just wanted it set up as a big studio where the heaviest piece of equipment would be a 3-400lb sewing machine, few tables, desk, computer, and etcetera. If possible I would like the loft to be free spanning so that it does not interfere with the shop down stairs. I am hoping even though it is a 40' span that being a lighter duty use would mean that vertical supports in the center could be avoided. I have emailed 15+ engineers all of which have chosen to not reply or bow out being uncertified in Washington. I don't know if that is due to my project being ridiculous or not large enough being a single floor design to capture their attention. For now I am just trying to determine the type of materials that would be required to make a free spanning floor to code so that we can put together an estimate of what this project would cost. Then I can determine if the cost savings are significant enough that it would be worth working around a post or two downstairs in the shop to support the center of the floor.

If anyone is just curious enough to crunch some numbers that be great to help us determine some actual costs of this project overall. If there are any engineers out there interested in a side job I am more than willing to pay someone for their services, please contact me at [email protected]. Once I can determine a cost and all that is involved I planned to talk to the city to pull actual permits. At that time it will have to submit drawings in triplicate with an application that the city engineer can sign off that the floor will support local codes. But beforehand I need to put together a cost by determining what would be involved and which way we would approached the project construction wise to make sure we even have the funds available to take on this task. I am more than capable of the construction, but the math and formulas you guys use as engineers is way over my head and I don't intend to attempt them myself. I know where my expertise lie and I intend to stay in my lane. So I would definitely need some sort of a design / blueprints to follow before we can begin the actual construction to be sure exactly where all the beams should meet and how. But I am hoping someone may be able to help put together a rough estimate for now by letting me know what size beams I will need and how many so I can begin to source supplies and what they will cost.

Thanks for taking the time to read this and thanks in advance for anyone who takes the time to offer any real help. It will be in Everett, WA 98204 if that makes a difference, and city advises we follow the 2015 IRC building codes for an office upstairs and a garage / light duty manufacturing downstairs.

Thanks again, Greg
[email protected]

I spend some time playing in webstructural.com when I approach these projects. They have metal and wood in there and it does all of the structural calculations that your structural engineer does. But you have to know what it wants for input and what it saying in the output.

Your span isn't crazy and having 2' of floor thickness to use is nice. My first stop would be to the lumber yard and have them quote for i-joists (called "TJI" apparently). They and/or their suppliers will do all of the calculations. You can first check and see if you are in the realm of possibility first by checking the span tables in i-joist literature. In terms of strength for height the i-joists seem to be pretty good. Engineered floor trusses (made with 2x4's) end up being taller.

I'm not a structural engineer. I've just finished building a home shop and am in the design phase of a house.

Good luck!

-Jim

Eng-Tips Engineering Forums

Machinist's are not structural engineers.....Duh

Don't mean to rain on your idea but it does rain a lot in Washington State.

I have done a mezzanine close in size and relative position within a 25 foot tall concrete tilt up building and I wouldn't dream of doing this without a permit and a structure of that magnitude is going to require stamped engineering drawings before any city / county engineer approves it for construction. No one in their right mind would sign up for this job as a "side job".

First up for math - office space as you describe is minimum 50 lbs/sq ft . . . 40x40x50 = 80,000 lbs plus the weight of the floor structure itself . . . that is a hell of a seismic load that you are going to have to bring to the ground with cross braces to foundations. Your building likely has foundation pads loaded to 3000 pounds / sq ft. So 5x5 pad is 75kips that holds up any column weight plus roof weight plus snow load. Adding any weight to this will not be centered and create a moment load - not allowed in a typical building foundation. You need to talk to a structural engineer - lots of them in Washington state to choose from - where are you located and I can give you some contacts.

Do some math before you start - you would be surprised at what you are going to have to do to your foundation and bracing to meet code . . . costs quite a bit to saw cut your floor to augment your foundation to carry the additional load that the code requires that you build to (whether you plan on loading it to that level or not).

Speak to your local building department as it is what they control.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

I have spoke to the local permit department and they say to follow the 2015 IRC based on it's intended use. Then I need to submit drawings in triplicate along with the applications and pay the fees upfront. The first step is to talk to an engineer. That one guy was being a smartass about only machinists that use this website, I don't think he has any idea of how many actual engineers all over this site. I actually found this site thru a search engine searching for steel beam spans/loads and found an old thread on this site with a guy doing a similar but smaller project. That thread had a ton of engineers that chimed in doing all the math equations to determine the loads, deflection, etc the guy should expect from his beams and what materials he should actually be using. So I am hoping to catch some of the same people's attention with my project to either get some input or a referral to someone who wants to take the project on as freelance work. My next step is to determine what materials will be required to build the floor so that I can source supplies and put together a budget, followed by getting a set of drawings I can submit with the permit application.

This subject does come up a lot, and the answers are pretty much the same - hire a real engineer to design your project. You’re gonna have to do that eventually no matter how much you ask around on the internet. You need a local guy familiar with local needs and licensed to do the work. That is your shortest, best route to success.

viragocafe said:

I have spoke to the local permit department and they say to follow the 2015 IRC based on it's intended use. Then I need to submit drawings in triplicate along with the applications and pay the fees upfront. The first step is to talk to an engineer. That one guy was being a smartass about only machinists that use this website, I don't think he has any idea of how many actual engineers all over this site. I actually found this site thru a search engine searching for steel beam spans/loads and found an old thread on this site with a guy doing a similar but smaller project. That thread had a ton of engineers that chimed in doing all the math equations to determine the loads, deflection, etc the guy should expect from his beams and what materials he should actually be using. So I am hoping to catch some of the same people's attention with my project to either get some input or a referral to someone who wants to take the project on as freelance work. My next step is to determine what materials will be required to build the floor so that I can source supplies and put together a budget, followed by getting a set of drawings I can submit with the permit application.

Click to expand...

That would be me sir.

I am a designer/engineer, I have done design's just like what your asking about,
the calculations, and presented to a P.E. for final approval & sign off.

So my answer has no "smartass component" in it, just the facts.

Please consult the archives, this has been discussed many times ad nasueum,
Post #7 from Henrya sums it up, your trying to get free professional engineering
services.

Another alternative would be to talk to the pre-fab mezzanine people. They have already done the engineering, and can help you with every aspect of this type of project. I worked for a major company with an in-house structural engineering staff and full fabrication shops, and the pre-fab mezzanine came out substantially less expensive than it would be for us to design and fab it ourselves. We even used their labor to install.

I don't recall the company we used.

Is the engineering system different in the US? In Canada work like this is regularly done by a provincially licensed P Eng. and not by a sub trade to be signed off at a later date by a P. Eng. In fact, of the folks I know, those that didn't get P. Eng. status usually don't call themselves engineers.

L7

You are correct about a lot of engineers on this web site. Engineers also know their limitations. That's why you need to talk with a structural engineering firm in your area. If the work is to be done in a coded area, you will need a PE signature on the drawings anyway.

Tom (one of those engineers)

You need an engineer licensed in Washington State.
Not some guy on the internet.
You need somebody familiar with your seismic zone, who can find out about your soil conditions, who can look at the plans, if you have them, of your existing building.

I hire engineers pretty often to design much more unusual stuff than this- its not that difficult, or expensive.
Find somebody local.

It will save you money, time, and hassle.

Dunno where you are in Washington, but my friends who are architects who do unusual steel framed buildings use these two engineers-
Ashley & Vance
kingworks

I would recommend the trusses made from 2x4's over TJI's anyday. The trusses are much stiffer, Your building will not collapse if they get wet and if you ever have a fire the second floor will stay in place for a little bit at least for it all comes down.

The biggest advantage to the trusses is that when you run all your wires and plumbing you have a ton of room and flexibility how you do it. Trusses make it wide open in all directions.

Sorry, but TJI's suck.

Our steel building has 12 inch tall girders made from rolled 12 ga galvanized steel back to back to make I beams then floor joists are 6 inch z of 14 ga.

Real strong stuff then flooring is 48 inch span rated ply with joists at 16 so it is somewhat strong, fire resistance on structure not issue.

Consider rolled formed steel as it may be a better fit.

But local engineers would have different ideas based on their preferences.

Usually the inspector has seen many local variants of what you are wanting to do.

They may be able to steer you to a local engineer who would have a better option for your taste and budget.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

You're not going to be able to beat the cost of the pre-engineered mezzanines. First, they can spread the design cost over however many hundreds of the model they sell. You're paying for all the engineering time for a one-off.

Second, they're ordering the materials in volume with negotiated prices. You aren't.

Third, they've done this before and know the pitfalls. You don't, so you'll probably end up going 50% over time and 50% over budget due to the learning curve. I know that's what I budget if it was me.

The other nice thing about the pre-engineered stuff: It's just a fixture. If you move or need to re-configure, take it down and take it with you. Something built into the building? Not so much. Even if 25' tall is way too high for your needs, it might not be for the next guy.

viragocafe said:

I have spoke to the local permit department and they say to follow the 2015 IRC based on it's intended use. Then I need to submit drawings in triplicate along with the applications and pay the fees upfront. The first step is to talk to an engineer. That one guy was being a smartass about only machinists that use this website, I don't think he has any idea of how many actual engineers all over this site. I actually found this site thru a search engine searching for steel beam spans/loads and found an old thread on this site with a guy doing a similar but smaller project. That thread had a ton of engineers that chimed in doing all the math equations to determine the loads, deflection, etc the guy should expect from his beams and what materials he should actually be using. So I am hoping to catch some of the same people's attention with my project to either get some input or a referral to someone who wants to take the project on as freelance work. My next step is to determine what materials will be required to build the floor so that I can source supplies and put together a budget, followed by getting a set of drawings I can submit with the permit application.

Click to expand...

Yes there are a ton of engineers on this forum. They are generally very helpful in offering advice especially on what *not* to do.

However - a lot of the time that advice is offered to fellow members with long track records of posting here, and everyone has a good feel for the level of knowledge/common sense of the person asking for advice. The answers get tailored accordingly.

You have no track record and nobody knows what you know, if you'd follow advice or whether you know enough yourself to give correct information for any answers to be valid. I doubt anyone is going to risk offering you actual calculations.

I've been here myself with a couple of building designs that I've personally constructed. I hired a professional engineer and happily paid his fee. Some stuff really is worth paying for.

PDW

Ries said:

You need an engineer licensed in Washington State.
Not some guy on the internet.
You need somebody familiar with your seismic zone, who can find out about your soil conditions, who can look at the plans, if you have them, of your existing building.

I hire engineers pretty often to design much more unusual stuff than this- its not that difficult, or expensive.
Find somebody local.

It will save you money, time, and hassle.

Dunno where you are in Washington, but my friends who are architects who do unusual steel framed buildings use these two engineers-
Ashley & Vance
kingworks

Click to expand...

Thank you this is what I was looking for. I said in my original post in case it was too long for everyone to have noticed that I am looking to "hire" an engineer not trying to scam someone into getting free advice as someone else basically put it. But I have emailed multiple engineers over last couple weeks that I found through search engines, probably 10-15 in my state which only 1 has bothered to reply as of this afternoon so far. I placed this post days ago however being anxious to put together even just a ballpark estimate as to whether the materials will cost $3,000 or $30,000 for now. I had hoped it would be possible I stumbled across someone who had done a similar project who could tell me that I could expect to use something like "this many" of "these sized" beams so I could source whom ever could supply them for the best price in my area and put together a rough budget of materials based on what someone else project required was that was similar in size and cost maybe $15,000 in materials so we could be in the range of say $15-$22,500 or so based on the other poster who recommends adding 50% onto a budget for extras. I am planning to purchase some rather expensive CNC equipment which is going to require some 3 phase power and whether I can do that this year or have to put it off till next is all based on what the floor will cost. With this other guy claiming he did it for $4000 that sounds way to low and being unable to get a hold of a firm in my area so that I can move forward, it has my mind spinning on this subject none stop for weeks now in regards to what will I and what I won't be able to make happen this year. Like I said I am just try to get a budget not get free engineer to do the whole project.

I talked to another guy selling steel for a similar project only his was 30'x35' and he claimed that after his engineer designed it to code for our area and holding 30,000lbs his material cost was only like $4000. This sounded insanely too cheap to me and I was curious as to if this was correct info? Then if it was why was he selling all his steel and trying to go as he put it a different route after hiring an engineer and buying all his required materials only to sell it all off at a 30% loss? I don't trust his project and info as being accurate enough that I can use it to estimate what my projects materials could run even if I estimate my project at 50% larger $6000 just sounds too good to be true to build my floor. I have drawings from the actual building engineers but they are in 98kb PDF files the site won't allow me to upload. I will contact those 2 firms you mentioned hopefully they will get back to me so I can move ahead with an accurate list of materials to build a budget from so I can actually move forward and stop the endless wonder of how far this project will be able to be taken this year. Thanks for the advice.

Comatose said:

You're not going to be able to beat the cost of the pre-engineered mezzanines. First, they can spread the design cost over however many hundreds of the model they sell. You're paying for all the engineering time for a one-off.

Second, they're ordering the materials in volume with negotiated prices. You aren't.

Third, they've done this before and know the pitfalls. You don't, so you'll probably end up going 50% over time and 50% over budget due to the learning curve. I know that's what I budget if it was me.

The other nice thing about the pre-engineered stuff: It's just a fixture. If you move or need to re-configure, take it down and take it with you. Something built into the building? Not so much. Even if 25' tall is way too high for your needs, it might not be for the next guy.

Click to expand...

I have looked into these and they do not offer any kits the size I require so that it would end up still being a custom 1 off. I also did finally hear back from 1 of the many engineers I reached out to in Washington State and I guess there is a code that if you build a mezzanine or loft it can not cover any more than 1/3rd of the floor space downstairs. So technically I have to build a 2nd story, how this changes things I am not sure I forwarded him the engineering drawing of the actual building he requested along with additional info about the floor I wish to build. So I am back to the waiting game but at least I have been in contact with an engineer capable of doing the work I need in my area. His prices of $100 per hour sounds reasonable for the work he does. We charge close to that just for upholstery work and that didn't require anything close to the college education an engineer goes thru. He says after he looks over all my info he will be able to give us an idea of what he will charge to do the work all together so that we can build an accurate budget as well as have the stamped engineers plans ready for the permit process.

viragocafe said:

I don't trust his project and info as being accurate enough that I can use it to estimate what my projects materials could run even if I estimate my project at 50% larger $6000 just sounds too good to be true to build my floor.

Click to expand...

Yeah, you can't take floor area cost when it involves increase span and scale accordingly, as span increases costs will increase in a non linear fashion. As the above posters point out you have to consider the increasing foundation requirements too and that really bumps the cost.

The reason for the enginer is not just the maths which IMHO you want to do and check yourself as well as getting them to so them!! its all the other code compliance issues and ways - cost effective ways around them they can bring to the table.

kb0thn said:

I spend some time playing in webstructural.com when I approach these projects. They have metal and wood in there and it does all of the structural calculations that your structural engineer does. But you have to know what it wants for input and what it saying in the output.

Your span isn't crazy and having 2' of floor thickness to use is nice. My first stop would be to the lumber yard and have them quote for i-joists (called "TJI" apparently). They and/or their suppliers will do all of the calculations. You can first check and see if you are in the realm of possibility first by checking the span tables in i-joist literature. In terms of strength for height the i-joists seem to be pretty good. Engineered floor trusses (made with 2x4's) end up being taller.

I'm not a structural engineer. I've just finished building a home shop and am in the design phase of a house.

Good luck!

-Jim

Click to expand...

That is a cool website but I do not even remotely know enough about the terminology to use it. I know the local codes for uniform and concentrate but they are in psf that site wants something called kips/ft where I don't know how those two numbers convert. It definitely is not psf since when I entered 50psf for the uniform load over 40' it was saying even a w30x108 beam would fail. I am pretty sure that means a 30" beam weighing 108lbs per foot (I am not even sure that is 100% accurate) which sounds like a massive beam yet failing under that weight so I am definitely not qualified to use that site to even work up a ball park on my materials. It looks super handy for those people that know the information where you can just punch in your info and bam you just load tested your beams. Autocad has a program Robot Structural analysis that does all that and then some where I believe you can design the entire building then load test it for structural integrity. It must have completely changed the engineering field over the last 5-10 years immensely and the amount of actual math equations they have to do ny hand.