Designing a garage; engineering help?

Below are a couple pictures of the garage I'm planning. Its cut into a hill and there will be access to a parking mezzanine from the upper end. I have contacted a few companies about the mezzanine construction and they say it will have to be almost two feet thick concrete with all kinds of crazy steel reinforcement which will more than double the cost of the entire project.

Can you wise folks take a look at the idea and tell me if there is a better way than $19,000 worth of concrete to accomplish this goal? I will need to park three vehicles on it and I'm sure there will be random things on it like a shelving unit with parts and maybe a lawn mower or two, but I'm making a generous estimate of 15k lbs.

How would you make this mezzanine?

BTW: 40x60 structure with a concrete block wall base.

a couple of 6" I beams supported on some 4" round steel tubes, some 2X3 steel cross beams, and wood decking?

While I'm only half an engineer currently, and not a civil. I'd think you'd be better off without any concrete other than the footings. Framing the deck entirely in steel and decking it with heavy wood. That wall will need to be extra beefy.

I was thinking back to some of the barns I used to know.... many of them had big wooden posts and beams with 2" oak planks as flooring. They supported massive combines and implements for 100 years. I have to think that I can support a few cars for less than $19k

What about standard floor joists spaced every 12" instead of 16"... or every 8"? It needs to be done right, but 20" of concrete (like they suggest) seems way overkill.

Is there a source where I can use common building materials to estimate weight capacity? Some website? a downloadable software? The design software I have is from the company who makes the buildings and I'm sure they are covering their butts by going overkill.

Kenny_McCormic wrote: That wall will need to be extra beefy.

Which wall? The side walls? I was thinking that a standard block wall would do, especially since I would support the floor with some sort of posts or stud walls under it. It doesn't need to be clear span.

The foundation footers can be dug a little deeper if needed. I'm doing my own excavation and calling the concrete trucks myself.

didn't you post a similar question a few months ago?

if so, i still say you should make the floor in at least one bay of the upper level have removable panels in the middle to allow you to work on the bottom of a car.. or maybe put a 4 post lift there to use as an elevator..

novaderrik wrote: didn't you post a similar question a few months ago? if so, i still say you should make the floor in at least one bay of the upper level have removable panels in the middle to allow you to work on the bottom of a car.. or maybe put a 4 post lift there to use as an elevator..

Yes, we did have this discussion...

(no 4-post lift will go high enough to use as an elevator)

I agree about using wood decking like an old barn. Good luck getting any inspector to sign off on it if it looks like a garage. Not saying it makes any sense, just is...

20" of concrete sounds excessive. That can't be right. Do you mean 20" of total structure including the support steel? That doesn't sound unreasonable assuming corrugated steel decking with 4-5" of concrete poured on top and support steel below. $19K may be more than you want to spend, but unfortunately that sounds like a decent price for what you're trying to do. Sorry.

Dunno how important it is to park on the top level but sounds like it's getting pretty expensive. I'd excavate the hillside out and park on the first level, build the second level w/ wood frame construction and use as shop space/ loft storage. Same square footage, way cheaper.

In reply to fasted58:

We suggested that in the last thread... he has his heart set on that mezzanine...

fasted58 wrote: I'd excavate the hillside out and park on the first level, build the second level w/ wood frame construction and use as shop space/ loft storage. Same square footage, way cheaper.

I like this - I am cheap.

The problem with wood is that it creeps under load, especially light members like 2xs. Conventional stick framing may support the load, but it's going to sag over time.

We built a large barn for vehicle storage over a basement and used 8x12 or so OAK - not pine - main beams at about 16'-0" centers, supported on 8x8 oak columns between each bay (call it a 12'-0" span). These were spanned by 3x8 oak joists at 24" centers, then covered with 2x4 oak T&G flooring. It was all oak which is much stiffer and harder than any of the strucutral pines. WAAAYYYY more butch than an overbuilt residential floor.

Curtis, I know it's not grassroots, but this is a job best left to a pro in some ways. Find a small structural engineering firm and ask them to design the cheapest floor for you that will support the load.

You're going to need them to engineer that retaining wall anyway. Retaining walls are more than just a beefed up basement wall, too.

I don't know where you're located, but I can't see the building department issuing a permit without signed and sealed construction drawings, and nobody should be rubber stamping something of this magnitude that they didn't design.

If this was a pole barn on flat ground, no problem. But the mezz and the retaining wall throw a couple curveballs into it. If you spend $1500 or $2000 on an engineer it will be a bargain in the long run.

Here's a guy I know that had a similar problem and his solution:

http://newhillgarage.com/other/construction-of-the-new-hill-garage/

Duke wrote: We built a large barn for vehicle storage over a basement and used 8x12 or so OAK - not pine - main beams at about 16'-0" centers, supported on 8x8 oak columns between each bay (call it a 12'-0" span). These were spanned by 3x8 oak joists, then covered with 2x4 oak T&G flooring. It was all oak which is much stiffer and harder than any of the strucutral pines. WAAAYYYY more butch than an overbuilt residential floor.

I'd make a wild guess all of that oak would cost damn near $19K if not more.

What Duke said is like deja vu... I think Curtis is hoping some gullible structural engineer has joined the forum since the last time he posted about this. Unfortunately for him, I know from experience engineers have "conservative paranoia" pounded into them at school from day-one. Seriously, it was part of orientation on my first day. So engineers tend to be risk-adverse in general and structural engineers x10 since when they eff up, things can fall down and people can die.

In reply to Basil Exposition:

Pre-cast panels was the first thing that came to mind, but if Curtis doesn't want to pay an engineer, I doubt he'd splurge for those.

You will not need 20" of concrete.

You WILL need about $19,000 AND a structural engineer.

You are not supporting 15,000 lbs. You are supporting a potential 5000 lb point load on virtually any point of the floor.

The retaining wall + the load = structural engineer, no options.

You can't engineer that off a free website.

If you have a legit quote from a stamped engineering/construction firm to build you a concrete Mezazinne that they rate to support 3 cars for $19K I would RUN not Walk to your bank and have that check cut. If it includes the retaining wall extra supper bonus.

To entertain myself I estimated the cost to produce a Loft that would seem to be of sufficient size to support the kinds of loads your talking about. Disclaimer: this is for COST ESTIMATION ONLY and is in no way indicitive of the size, dimension, or design of lumber that would be suitable for your application. Persuing anything like this would be at your own peril and you take 100% responsibility to do your own load calculations/hire a stamped engineer to design a proper mezannie for you.

So If I assuem that the Mezazine would be 40' wide x 20' long one could go about it in the following way. Make proper footings for 20 poles as you have drawn. Rows of 4 poles per row 1 on the wall, 3 rows in the middle of the garage floor and 1 more row on the other walls. Put 12-8x8 posts of high quality lumber in the 3 middle rows and 8-6x6 posts on the wall rows. On the 20' length run 1-3/4 x 18" 20' LVLs as beams on the 20' axis on top of the posts. 2 on top of the 6x6's at the walls, 4 each beam on top of the 8x8's. So now we have 5 20' long beams made out of 18" high LVL's spaced 10' on center. Now take 12' long 1-3/4 x 14" LVL's and put them along the 40' axis across the beams spaced every 12" (OR less again need an engineer to do calcs). You'll need 80 of these beams. On top of all this create a deck out of 3"x12" bridge planks. You may want to consider ruining several routers cutting TNG into the side of these or find some at a lumber mill precut with TNG. You'll need 200 12' boards. Put all this together with proper fasteners, cross bracing, proper footings and a proper retaining wall and you'll have a Lumber mezzaninee that may hold up your cars.

Total cost today from Menards for the lumber I just described.. $18,173. Which is why I would JUMP on a quote for 19K worth of concrete.

SVreX wrote: The retaining wall + the load = structural engineer, no options.

We sell piping expansion joints and guides. Reps ask us to design the anchors for these systems and we always refer them to a structural engineer.

They ask if we can just do it over the phone or if they can give us a print to review. No, you need a structural engineer and we get the usual reply of: you sure?

In reply to Datsun310Guy:

It's all fun and games until the joint/guide/safety valve can't do what it's designed to and pipes under pressure go pear-shaped.

BTDT... (specifically, we got to fix the aftermath). It ain't pretty. They were picking pipe pieces out the side of buildings hundreds of feet away. Minor miracle nobody was killed or injured.

Dammit.... I hate it when you guys are right. It took seeing the math.

novaderrik wrote: didn't you post a similar question a few months ago?

Yup. Then I tried to resurrect it and nobody bit so I started a new one.

Curtis:

Where are you located? I can recommend a structural engineer who will NOT overdesign it, but who will give you good, cost-effective advice.

If you are still in P-burgh, he can probably cover you.

Tom Woods, PE
Baker Ingram Associates
Newark, Delaware
366 East Main Street
Newark, DE 19711
302-456-1757 ph 302-456-1759 fax

They have PA offices, but Tom is the guy I know best, and he is registered in PA. He's a good sensible engineer. Call him and tell him I sent you (Duke Wilford from FC Architects); he'll at the very least give you some good advice. His professional services fees are really reasonable, too.

I would go steel. I beams with concrete or steel columns should be the most cost effective way to do it. I would also suggest a pre-application meeting with whoever you will be getting permits from so you know exactly what they will be looking for. You will definitely need some sort of structural analysis by a licensed structural engineer.

Note: I am a civil engineer, but not a structural.

bgkast wrote: I would go steel. I beams with steel columns should be the most cost effective way to do it.

I agree with this, with metal deck and probably 6" reinforced poured concrete over it. You may also find precast concrete planks are cost effective, but I don't know if they would be in small quantities like this.

Here is a dumb question but would it be possible to just enlarge the building to make up for not having the second level? It seems like that might be more cost effective.

curtis73 wrote:

Kenny_McCormic wrote: That wall will need to be extra beefy.

Which wall? The side walls? I was thinking that a standard block wall would do, especially since I would support the floor with some sort of posts or stud walls under it. It doesn't need to be clear span. The foundation footers can be dug a little deeper if needed. I'm doing my own excavation and calling the concrete trucks myself.

Use the walls as footings for the I beams, then perhaps some cross structure over that, followed by heavy wood decking. That's how I imagine it would be cheapest to do.