Building my mezzanine: Questions, suggestions, Help?

[deucenut]

Well it's finally time to build my mezzanine. When our house was built, I managed to convince my wife to let me get the garage built extra deep. :thumb up: So I ended up with a 19'6"wide x 29' deep garage with a 13.5' high ceiling. So I am going to build a mezzanine next to the stairs from inside the house.

PLAN:

My plan is to have a 16' wide x 10' deep mezzanine. I plan to use (3) 2x12's glued and nailed together as my front beam(span is 16'). I will use 2x10's for the joists which will be 12"o.c. and have joist hangers at each end.(I am not cantelevering the joists as I want to maximize head room, both above and below the mezzanine). The joists will have two rows of 2x10 blocking with the rows spaced evenly in the 10'. I am planning to use a 6x6 post at either end of the beam that sits on the concrete floor. The ledger will be a doubled up glued and nailed 2x12s. The flooring will be 1/2" or 5/8" plywood. All 2x's will be spruce with the 6x6 posts being fir.

QUESTION:

Will using a tripled 2x12 be strong enough to span 16'? I plan to use the area as storage and work space so a lot of weight will be up there.

I don't want to put a post in the middle of the beam span because I want to put a car sideways under the mezzanine. Thanks in advance for the help

 

[Cyberbear]

It sounds like good solid construction but you'll need to check with your local building dept. to verify the span loads. My particular mezzanine has 2 x 12 @16" o/c floor/ceiling joists with 3/4" ply on top, and span 15" w/o problem. Better too much than not enough.
I'd think your 2 x 10 @ 12" o/c will be more than adequate as a mezzanine storage floor.

 

[Ironcrow]

How's the ridge beam rated? Could you hang the center of the mezzanine from the ridge to avoid a column?

I'd tend to use steel instead of sistered lumber.

 

[deucenut]

The second floor of my house is above the garage. So I don't really want to hang from the ceiling to avoid a post. That's why I was hoping a tripled up 2x12 would he strong enough to support the 16' span with the 2x10 joists. I just don't want sagging and unsafe conditions. I tried to use a beam calculator from the Internet, however I don't know what the live load or dead load will be.

 

[someguy11]

I put a loft in our garage. I started a thread about it on this site.

You need to consult beam tables for various spans and loads.

I tried using dimensional lumber (ie 2x12s) but the strength factor is not good enough for beam use for generally available lumber. I ended up using LVLs, which worked great. My span was 22 feet clear. I used 2 inch x 11 3/4 beams, IIRC.

You can also use I joists.

Gluing and screwing beams together to form one beam is tricky. The glue has to be non creeping for beam use. Google it. Not many are. The screws have to be carefully placed for proper load transfer between the pieces. I looked into this and decided it wasn't worth the hassle and went with LVLs.

BTW, most inspectors will NOT pass a structure with a beam in that they cannot verify the strength of and they want to see that some load analysis was done, ie someone consulted a beam table at the very least.

If you speak to your local building supply store and tell them you want to buy LVLs, they usually have a specialist that will help you size them for your application.

I know a guy that built an elaborate garage structure without engineering and without a building permit. His neighbors complained. An inspector came on site, looked at the engineering or lack thereof, and ordered the building taken down. It can happen.

I didn't get a permit for my loft. It is structural so theoretically, it is required. I did, however, make sure that it was engineered correctly so that there are no complaints if it is inspected.

 

[theoldwizard1]

Will using a tripled 2x12 be strong enough to span 16'? I plan to use the area as storage and work space so a lot of weight will be up there.

At first I was thinking overkill, but with a significant dead load AND a live load, you are good ! You might check into the price of a glulam, but they will ask you for dead and live loads for proper sizing. (The main beam in my house is a triple 2x12, but the piers are 8'.)

The 6x6 post can be untreated if the are resting on 2"x8"x8" PT, maybe even double them. Make sure the are well anchored to the floor and the 6x6 (you can use 3 - 2x6) are well spiked in.

I would run 2x4s at each stud down from underneath the ledger to the floor. Either PT or resting on PT pads.

1/2" plywood is kind of sketchy. I would probably use 3/4.

Buy the appropriate Simpson Strong Tie screws. Not cheap, but the will make installing the joist hangers SO much easier !

 

[deucenut]

At first I was thinking overkill, but with a significant dead load AND a live load, you are good ! You might check into the price of a glulam, but they will ask you for dead and live loads for proper sizing. (The main beam in my house is a triple 2x12, but the piers are 8'.)

The 6x6 post can be untreated if the are resting on 2"x8"x8" PT, maybe even double them. Make sure the are well anchored to the floor and the 6x6 (you can use 3 - 2x6) are well spiked in.

I would run 2x4s at each stud down from underneath the ledger to the floor. Either PT or resting on PT pads.

1/2" plywood is kind of sketchy. I would probably use 3/4.

Buy the appropriate Simpson Strong Tie screws. Not cheap, but the will make installing the joist hangers SO much easier !

Overkill is what I was going for since I am not really sure what the loads will be. I would rather have it over-built than under-built. The last thing I want is for it to come crashing down on my Deuce, or worse yet, my daughter who likes to be in the garage with me.

A couple questions about your post:

Are you suggesting pressure treated pads under the posts for moisture protection from the concrete? It'll be indoors and see no moisture. Does concrete inherently have some moisture?

I was going to drill a hole in the concrete floor a set a saddle of some sort on the floor to anchor the posts. I was thinking this would be sufficient.

Your idea of running 2x4's under each joist from the ledger to the ground is a good one. I think I will probably do that, even though I plan to put 32 6" lag bolts through the ledger into the wall studs. There's nothing wrong with overkill in my book, especially when I am not really sure how much weight I am going to put up there. At one time I was considering building a deuce chassis up there, but I have no way to get it up or down…lol. And I was afraid that may have been a wee bit too much weight(around 1500 lbs I would guess).

My next door neighbour built a mezzanine in his garage that is the full width and approximately 15' deep(nearly the entire garage). He invited me over to show me how he did it. He used 2x12's tripled for the beam, but they weren't 20' long….he had joined them and overlapped the joints with no post under the overlap. He also only used nails to secure the ledgers to the wall studs. He didn't do much blocking either. Needless to say, I didn't wanna walk on it….lol. He was very proud of his structure so I didn't say too much. But this is exactly what I want to avoid.

Again, thanks to everyone for the assistance and keep it coming.

 

[AMCguy]

Excellent! Another mezzanine build. Please post pictures of your progress.

I built mine (similar in size) a couple of years ago and posted about it here. I got lots of input and advice along the way. Of particular value, was the advice on member size and loading. Here's a link to the thread;

http://www.garagejournal.com/forum/showthread.php?t=234134

And for the lighter side of mezzanines, here's a link to another one I built.

http://www.garagejournal.com/forum/showthread.php?t=134044

 

[Ironcrow]

LVL are good too. With no pier under the 6x6 posts, you might want to spread the load a little there too. I'm sure an architect would have at least thickened the pad where the posts land, whether or not it is needed.

 

[theoldwizard1]

And for the lighter side of mezzanines, here's a link to another one I built.

http://www.garagejournal.com/forum/showthread.php?t=134044

Any mezzanine built without supports under the ledger board is for "light" storage only. Nothing wrong with it as long as your aren't storing engines or transmissions up there !

Dirty Harry : "A man's got ta know his limitations !"

 

[theoldwizard1]

Are you suggesting pressure treated pads under the posts for moisture protection from the concrete? It'll be indoors and see no moisture. Does concrete inherently have some moisture?

YES !

I was going to drill a hole in the concrete floor a set a saddle of some sort on the floor to anchor the posts. I was thinking this would be sufficient.

Probably. The best answer is cut out a 2'x2' section of floor and dig down at least 2' and fill with concrete. Cut some piece of rebar, wire then together in a grid and place it in the middle of the pour. Attach your mounting bolts for the bracket before it sets. You need to give it a couple of days before your build on top.

Your idea of running 2x4's under each joist from the ledger to the ground is a good one. I think I will probably do that, even though I plan to put 32 6" lag bolts through the ledger into the wall studs.

Lags alone are really never a good idea for a ledger that is carrying a live load. The bouncing from people walking on it will cause them to loosen over time. Make sure to pre-drill the holes for the lags or you might split the stud.

He also only used nails to secure the ledgers to the wall studs. He didn't do much blocking either. Needless to say, I didn't wanna walk on it….lol.

Again, live load will loose those nails over time.

 

[shortykorte]

Recommend 3/4 tongue and groove subfloor plywood for deck.

 

[deucenut]

YES !


Probably. The best answer is cut out a 2'x2' section of floor and dig down at least 2' and fill with concrete. Cut some piece of rebar, wire then together in a grid and place it in the middle of the pour. Attach your mounting bolts for the bracket before it sets. You need to give it a couple of days before your build on top.


Lags alone are really never a good idea for a ledger that is carrying a live load. The bouncing from people walking on it will cause them to loosen over time. Make sure to pre-drill the holes for the lags or you might split the stud.

I understand the reasons behind concrete footings. But in my case is it really necessary?

When they poured the concrete floor in the garage it ended up being about 6-7" thick at the back(where the mezzanine will go) since they needed to slope it and wanted to end up with 4" at the garage door. It also has extensive rebar in it. Also, one post will sitting on the concrete foundation wall since it will actually be hidden in the wall behind the drywall.

 

[deucenut]

Recommend 3/4 tongue and groove subfloor plywood for deck.

I was wondering about this and whether 1/2" plywood would be good enough. Thanks for the suggestion. I think I will go to this as it's not too much more money.

I've been thinking about what will be stored or worked on in the mezzanine. I plan to put my toolbox up there(pretty heavy) and my future compressor. The one I want is 285 lbs. So right there I bet thats a total of at least 600 lbs. Then I plan to build a work bench, shelving units and store probably another 1500 lbs. I plan to keep most of the heavy objects against a wall and away from the beam.

 

[Bib Overalls]

You can glue and nail (I'm using a lot of deck screws these days) 2x4s to the beam and ledger forming shelfs for the joists to rest on. Toenail (or screw) the joists in place. Pressure blocks will keep the joists from twisting.

 

[theoldwizard1]

I understand the reasons behind concrete footings. But in my case is it really necessary?

When they poured the concrete floor in the garage it ended up being about 6-7" thick at the back(where the mezzanine will go) ... It also has extensive rebar in it.

If what you say about the thickness and rebar is accurate, then you are probably good.

Recommend 3/4 tongue and groove subfloor plywood for deck.

I was wondering about this and whether 1/2" plywood would be good enough. Thanks for the suggestion. I think I will go to this as it's not too much more money.

Absolutely !

 

[tractordude]

I built one using some left over 4x4's and 2x10's. It's about 10'x12'. A buddy found me a new in the box retractable attic ladder at a garage sale for $25.
I had to cut some of the ladder off, as my mezzanine is only 6 1/2 feet tall.

 

[pmiranda]

I understand the reasons behind concrete footings. But in my case is it really necessary?

Depends on the the concrete strength, and how much load you're putting on those 6x6's. Do the math.

 

[bczygan]

Well it's finally time to build my mezzanine. When our house was built, I managed to convince my wife to let me get the garage built extra deep. :thumb up: So I ended up with a 19'6"wide x 29' deep garage with a 13.5' high ceiling. So I am going to build a mezzanine next to the stairs from inside the house.

PLAN:

My plan is to have a 16' wide x 10' deep mezzanine. I plan to use (3) 2x12's glued and nailed together as my front beam(span is 16'). I will use 2x10's for the joists which will be 12"o.c. and have joist hangers at each end.(I am not cantelevering the joists as I want to maximize head room, both above and below the mezzanine). The joists will have two rows of 2x10 blocking with the rows spaced evenly in the 10'. I am planning to use a 6x6 post at either end of the beam that sits on the concrete floor. The ledger will be a doubled up glued and nailed 2x12s. The flooring will be 1/2" or 5/8" plywood. All 2x's will be spruce with the 6x6 posts being fir.

QUESTION:

Will using a tripled 2x12 be strong enough to span 16'? I plan to use the area as storage and work space so a lot of weight will be up there.

I don't want to put a post in the middle of the beam span because I want to put a car sideways under the mezzanine. Thanks in advance for the help

There is no way to know if your proposed structure is adequate without knowing the anticipated loads and their layout.

In general, dimensional lumber will support less than engineered lumber of the same depth and that less than steel.

Will this be inspected?

What is your layout and proposed loads?

For example, 2 - 1 3/4x11 7/8" 1.9 LVL's beam will support a load of 334#/LF at L/360. This means the beam will deflect (Sag is the wrong term) about 1/2". All beams deflect. This means you can have a combined Live and Dead load of 66.8#/SF.

Joists for this loading would need to be SPF#2 and better 2x8's at 16"o.c.

No need for 6x6 posts. Use 4x4.

Size the ledger LVL in a similar fashion, but put a support post in the middle and use a single member. A 1 3/4x9 1/4 would do it.

Bill

 

[deucenut]

Depends on the the concrete strength, and how much load you're putting on those 6x6's. Do the math.

The concrete is 28 psi...that's what I was told by the concrete truck driver.

 

[deucenut]

There is no way to know if your proposed structure is adequate without knowing the anticipated loads and their layout.

In general, dimensional lumber will support less than engineered lumber of the same depth and that less than steel.

Will this be inspected?

What is your layout and proposed loads?

Bill

I plan to store car parts up there. As well as have a large bench. I plan to put my tool box up there(I would think pretty heavy, 500 lbs?), my future air compressor(285 lbs) and a bunch of other "stuff". I don't anticipate storing engines or anything else that is super heavy like that. I plan to keep the toolbox and the air compressor back against the wall and away from the edge of the mezzanine.

One thing I don't understand...and some of you are probably gonna think this is really stupid of me, but why is an LVL stronger than dimensional lumber?

 

[bczygan]

I plan to store car parts up there. As well as have a large bench. I plan to put my tool box up there(I would think pretty heavy, 500 lbs?), my future air compressor(285 lbs) and a bunch of other "stuff". I don't anticipate storing engines or anything else that is super heavy like that. I plan to keep the toolbox and the air compressor back against the wall and away from the edge of the mezzanine.

One thing I don't understand...and some of you are probably gonna think this is really stupid of me, but why is an LVL stronger than dimensional lumber?

Because it is engineered that way.

First, for the same depth member, it is wider. 1 3/4" vs. 1 1/2", so the section modulus is greater. Secondly, it is more uniform in construction, without knots or defects. And third, the way the plys are oriented provide greater strength.

And for you, who needs to minimize the amount of height used up by the structure, they provide the optimum balance of cost and capability to support the loads. Steel could save some depth, but at greater cost and difficulty to connect to. And dimensional lumber to support the loads and span we are talking about will be a deep multi-member beam and difficult to properly construct.

Note that you need to specify the strength of the LVL in your calculations, in the above example a 1.9Fb was selected. It's like choosing one species or another in dimensional lumber. Some are stronger than others, by nature or by design.

LVL's are the correct choice.

Bill

 

[bczygan]

The concrete is 28 psi...that's what I was told by the concrete truck driver.

You mean 2800PSI.

You don't need to worry about the floor.

 

[bczygan]

How much height under the mezzanine?

With 13'6" total, minus a foot for the beam and say 7' clear under the beam, you only have 5 1/2 feet clear for the mezzanine. Is it just for storage?

Bill

 

[deucenut]

How much height under the mezzanine?

With 13'6" total, minus a foot for the beam and say 7' clear under the beam, you only have 5 1/2 feet clear for the mezzanine. Is it just for storage?

Bill

I'm planning to split the difference...sort of....there will be 6'4" above and 6'2" below the mezzanine. I will spend more time above then below it as I plan to store a car under it. I am 6'3" tall so I may have to duck or slump a little. But I don't want to go any lower cause the car I want to slide under it is 6' tall...probably about 6'1-2" tall when it's on my floor dollies.

 

[bczygan]

I'm planning to split the difference...sort of....there will be 6'4" above and 6'2" below the mezzanine. I will spend more time above then below it as I plan to store a car under it. I am 6'3" tall so I may have to duck or slump a little. But I don't want to go any lower cause the car I want to slide under it is 6' tall...probably about 6'1-2" tall when it's on my floor dollies.

Well, you have the structure calculations you need.

Now go build it.

Bill

 

[deucenut]

I know!! Was planning for this week but ended up working 3 OT shifts. Hard to find the time

 

[bczygan]

Please put your location in your profile and show us some photos!

Bill

 

[Ironcrow]

Is the front edge of the mezzanine open to the garage below? Will there be a railing? Wall?

 

[deucenut]

Is the front edge of the mezzanine open to the garage below? Will there be a railing? Wall?

It will be open to the garage below. I will be installing a railing for safety. I thought about a wall and didn't see a need for one.

 

[Ironcrow]

So, then is additional beam depth possible? The beam could protrude above the mezzanine floor level - allowing more flexibility in beam selection and managing desired ceiling heights.

 

[theoldwizard1]

So, then is additional beam depth possible?

The biggest issue with 2 beams would be additional cost.

Instead of spanning 10' from the back wall, he could put another beam at say 5-6' out. He could probably downsize the front and middle beams to 2 - 2x10 (like the back ledger) and the post to 4x6. The other joist could drop down to 2x8 but hey would double the number of joist hangers and fasteners (you can NOT use standard nails or screws on joist hanger) If he stay 16" O.C. and uses 3/4" tongue and groove plywood probably doe not need any additional blocking.

 

[deucenut]

The biggest issue with 2 beams would be additional cost.

Instead of spanning 10' from the back wall, he could put another beam at say 5-6' out. He could probably downsize the front and middle beams to 2 - 2x10 (like the back ledger) and the post to 4x6. The other joist could drop down to 2x8 but hey would double the number of joist hangers and fasteners (you can NOT use standard nails or screws on joist hanger) If he stay 16" O.C. and uses 3/4" tongue and groove plywood probably doe not need any additional blocking.

What kind of nails should I use? I was going to use "joist hangar nails"

 

[davo727]

If it were mine id slam a steel I beam in there 12 inch high by 4 inch wide, 19 lb per foot

 

[theoldwizard1]

What kind of nails should I use? I was going to use "joist hangar nails"

I have never seen "joist hangar nails" from a nail company.

The bracket hanger company usually sell nails/screws. Yes, they cost more, but you know they are right. The screws are great (and worth the extra) if you have an impact driver. Don't have one ? A good excuse to buy one !

Regardless of whose nail/screws you use make sure they are the correct length and diameter.

 

[deucenut]

I have never seen "joist hangar nails" from a nail company.

The bracket hanger company usually sell nails/screws. Yes, they cost more, but you know they are right. The screws are great (and worth the extra) if you have an impact driver. Don't have one ? A good excuse to buy one !

Regardless of whose nail/screws you use make sure they are the correct length and diameter.

I was told once to never use screws in the construction of framing, such as in joist hangars. Reason is because screws don't have the shear strength that a nail has. This true?

 

[pmiranda]

Yes, unless they are specifically made to be structural (Simpson sells some, which I think is what theoldwizard is talking about), screws are only for holding things in tension. They have relatively little shear strength. Even in bolts, you can only use the non-threaded portion to handle shear a given minimum distance from the threaded end.

And those little 1/4" impact drivers are a wonder for driving screws into lumber. No more stripped heads. I built a deck without one and it was a PITA compared to work I've done since then. Worth every penny.

 

[deucenut]

Yes, unless they are specifically made to be structural (Simpson sells some, which I think is what theoldwizard is talking about), screws are only for holding things in tension. They have relatively little shear strength. Even in bolts, you can only use the non-threaded portion to handle shear a given minimum distance from the threaded end.

And those little 1/4" impact drivers are a wonder for driving screws into lumber. No more stripped heads. I built a deck without one and it was a PITA compared to work I've done since then. Worth every penny.

I have a Makita cordless impact driver. Came in the case with the Makita drill I got too. I love them both. Amazing torque from the impact driver.

 

[theoldwizard1]

I was told once to never use screws in the construction of framing, such as in joist hangars. Reason is because screws don't have the shear strength that a nail has. This true?

This is why I said ONLY use the screws recommended by the joist hanger company ! Simpson LUS210 hanger require Simpson #9x1-1/2" Strong-Drive SD screws.

I have built a couple of lightweight storage lofts by running 2x4 cross joists with hanger between exiting garage joists and topping it with 1/2 plywood. With an impact the screws go in in seconds !!

 

[deucenut]

So I went to my local lumber yard today and began to spec out the beam for my mezzanine. The guy at the lumber store asked me a bunch of questions:

Load: approximately 3000 lbs
Span of beam: 16'
Size of area: 10'x16'=160 sq/ft

He told me the load would be approximately 20 lbs per sq ft and that a tripled up 2x12 would NOT be enough to carry that load. So I asked him what I would require. He used a beam calculator and came back with this:

5 ply 2x12 OR a 5" x 11 7/8th" LVL beam OR a 5 ply 11 7/8th" beam.

This seems like crazy overkill to me. I asked him if 2x10 dimensional lumber for the joists would be ok and he said "yes, no problem". But the beam vs joist strength seems very one-sided.

So, please, help me out here. Is this overkill? Can I get away with a tripled up 1 3/4" x 9 7/8" LVL or is a tripled up 2x12 dimensional lumber ok? I'd even be happy with a tripled up 1 3/4" x 11 7/8" LVL...which has GOT to be stronger than tripled up 2x12 dimensional lumber.