Garage Design

[Michael Oritt]

I am doing preliminary design of a garage and have a question for the smart guys here:

The building will be of frame construction and will be 25' wide. I would like to put a loft with a plywood deck over a portion of the main floor--the dimensions of the loft being 25' square. The loft would be used for light storage with weight being exclusively on the sides (not ends) and no appreciable weight in the center. I could tolerate some floor bounce if need be.

Here's the question: What size floor joists or fabricated wood trusses would I need to adequately support the loft without any columns to the concrete floor below--in other words using a free span--and on what centers would they need to be?

I have read from one site that 16" floor trusses on 24" centers will span 27-1/2'. Any input appreciated.

 

[GregW]

Hi Michael,
I'm not one of those smart guys your looking for, but I'll throw out a couple ideas. If you have a peaked roof for the garage, maybe you could suspend the center of the loft from the roof itself. The roof would have to be engineered to take the additional weight, but cables or steel could be incorporated. Another thought is to frame the loft with steel I-beams. Using a center beam, you could probably get away with only one support going to the floor. The center beam could also work as a trolley for an engine hoist.

 

[Randy_Gay]

Michael,
In my opinion that would be pushing it. You might want to look at 16" TJI-560 at 16" o.c. I would suggest having a structural engineer review your plan. The spans you're talking about are fairly large for frame construction, and a few hundred dollars spent now is good protection. Good Luck

 

[Cottontop]

Hi Michael,

Just a suggestion here, but what most structure designers do is to make the dimensions of the building, from the outside in. That is, to make the dimensions in multiples of the materials that are used for fabrication, instead of working from the inside out and having shortages or overages.

In other words, making a building 25' is not a multiple of 8 foot stock nor 10 foot stock. You'll need another foot for 8 footers and have a lot of leftover scrap for 10 footers.

As far as your ceiling joists, I think that you'd be able to buy steel trusses far cheaper than you can buy the wood to make wooden trusses. I also doubt that the dimensions and centers for the wooden trusses that you cite took into account having an attic full of car parts.

I agree with the suggestion that, to be on the safe side, you have a structural engineer or architect take a look at your plans. You may have it all covered, but it'd probably be worth a coupla' hundred bucks to NOT have your attic end up on top of your Healey.

Tim

 

[Cutlass]

Tim's on the right track. I'd get a pro to work out the structural design. I you buy pre-fab wood trusses, the truss company will help with actual dimensions of the wood for the trusses. You've got more to worry about than floor bounce. Snow loading is an issue up there in Md., isn't it? Done correctly, you will also need permits and inspections. Don't shy away from this part. Those permits and inspections are there for a purpose and will be a benefit for you. I built a garage for my playhouse many years ago, and did all of the above. A few extra bucks, for sure, but well worth it fifteen years later.

 

[Johnny]

Michael, If I were you I'd check locally for an architect to help in these areas. You'd be amazed how little it might cost and in the long run you're better off knowing the roof won't cave in on your lovely AH 100/4. When I had my garage addition put on I consulted with an architect and he drew up some suggestions with lots of advice, and it didn't cost me a dime. If you do hire them to complete the job they work hand in hand with the contractor. As an example, he suggested to the contractor to add some more support (roof joist's) to the extended roof to support car parts I plan on storing there.

 

[Sparkie93]

Michael,

I added an extra garage onto our house 5 years ago: 36' deep x 28' wide (26" wide for ~ 1/2 of it). There are no interior columns. I used 16" I-beams (LVL or whatever it's called) on 24" centers and have 20' x 36' storage room above with stairway for parts storage. Parts of two walls are attached to two exterior walls of the house. I had a fantastic carpenter frame it - he talked me into doing it this way where before I considered premade trusses, supplied through Home Depot. Technically I think I should have put the joists on 17-18" centers at the 28' span or doubled up every third one or so, but didn't. I have short wall at one end for the stairway and a 4' wall at the other end of the garage that help take some of the load. It's perfect for my needs. Had I thought I was going to make living space out of the upstairs I'd have probably checked into steel beams. As it is for storage I have no concerns.

I designed my garage myself, was general contractor, and did a reasonable amount of the work. A few minor things changed along the way, but considering my options (conforming to neighborhood covenants and staying within a budget severely limited me) I'm very pleased. As others have said, by all means consult an architect or someone in the building construction business for a professional opinion. A good structural engineering can educate you on truss design, whether premade or stick built. Also, no matter how solid the upstairs floor/roof structure is, the walls must support it all. I never even considered 2" x 4" studs, instead using 2" x 6"s.

Before you go too far, determine what it is you want in your new garage. My wife says there won't be a next time, but when I do this again some year I'm adding a lift, plumbing, HVAC....

Good luck,

Robert

 

[Michael Oritt]

Folks--

Thanks for all the good advise. It was never my intention to draw this up on the back of the napkin and build it--both the building and design will be professionally done. I amm simply fiddling with "pre-plans" to get an idea of how I might lay the building out and one factor (building/celing height involved the supporting rafters under the loft.

I will take the advise of several and plan on more stuff going up in the loft than I might now think and build it strong. I'm also going to reduce the building's width by one foot to 24' and so take advantage of dimensional lumber and have less waste.

Thanks again--Michael

 

[Richard Dickinson]

You might want to consider using wooden I joists they are readily available at most building supply places. A 14" I joist will span 23'-9" (between support faces)at 24" on center. This is with a live load of 40 pounds per sq. ft. and a dead load of 10 lbs per sq. ft. This is with 3/4" plywood deck glued and nailed to the top flange. This allows for a maximum deflection of L/490 which is stiffer than required by most building codes. Of course you want to check your local building code. Some suppliers may even be able to help with the design. Check the Georgia Pacific web site for more information.

 

[Cottontop]

Hi again Michael,

One more/last thing... You didn't mention anything about ceiling height on the ground floor, but in at least one bay, I would put in a 12-14 foot ceiling just in case you want to add a full lift sometime in the future.

A 60" tall car on a 72" tall lift needs a lot of UP space.

Tim

 

[Randy Forbes]

Hi again Michael,

One more/last thing... You didn't mention anything about ceiling height on the ground floor, but in at least one bay, I would put in a 12-14 foot ceiling just in case you want to add a full lift sometime in the future.

A 60" tall car on a 72" tall lift needs a lot of UP space.

Tim

I think he's designing the garage around the lift, so that's a given :wink:

 

[Michael Oritt]

Randy--

I am putting in a full height lift and there is plenty of headroom for it.

 

[Cottontop]

Randy, Michael,

I should have realized that a full lift was a given. That's what I get for not reading all of every thread every day.

I have a friend who built a 4 bay garage and put in a tall ceiling for a full lift. It was tall enough for ALL of his cars to clear the ceiling.

After retiring he decided he needed a new Ford 350 dually to pull his wife's new 5th wheel RV trailer.

NOW when he puts his nearly 7' tall truck on the lift and runs it up, the lift has to stop at about 5'. About a foot from being able to stand up straight under it.

Michael, just make sure that you put in enough UP room to last you for as long as you live there.

Tim

 

[Michael Oritt]

Tim--

The lift I am fixing on is the Eagle American 7000LP with a minimum pad height of 2"--the lowest I have found anywhere--which will be great for both my Healeys and the Elva Courier which have pretty low clearances of 3-1/2" and 4" respectively.

The swing arms in the symetrical configuration will clear the tailpipes and engage the longitudinal frame rails which interestingly is 19" wide on both the Healeys and the Elva.

This is an expensive lift but it offers a priceless advantage of low clearance plus it is made in America--many people feel that means alot both in terms of quality and other factors.

The area of the garage where the lift will be placed has about 14' headroom--more than enough--the lift height is 72" and max. capacity is 7000 lbs--plenty for any "little" car and will even handle my Toyota Tundra, though I don't (presently) do any work on it beyond filling the gas tank.

 

[Randy Forbes]

Michael, I must've missed it in the other thread, but which brand/model lift did you settle on?

 

[GregW]

will even handle my Toyota Tundra, though I don't (presently) do any work on it beyond filling the gas tank.

I need a beer and some time in the recliner after doing that. :laugh:

 

[anthony7777]

michael, google "glulambeams" they will also have a spec. chart, you will need permit/permits to do your job, i dont know what your building department is going to want as far as drawings but you should have some ready for them, include details of the ajoining framming i.e. supporting walls, type of foundation and any plumbing and electric that may have to be relocated, keep all the information on any fabricated structural material your going to use i.e. specs, some inspectors will want you to use a higher spec. rated structural beam then required, i know..i know.. but here in ct. its at the inspectors discretion. one last thing...dont argue with the inspector.. good luck!

 

[hilsideser]

My inclination would be to go to a building materials supply that <span style="text-decoration: underline"><span style="font-weight: bold"><span style="font-style: italic">builders</span></span></span> go to. Talk to a contract salesman and tell him what you're doing. They do this thing day in and day out. (forgive me Lord, for I am about to sin), but forget the architect and inspector. Put the money into materials and over build it; Glu=lam, etc.

 

[Cutlass]

I've got to disagree with Patrick, at least on the inspector point. I'm a muncipal court judge, and see the grief that befalls folks who fail to get permits and inspections. If you are caught building without a permit, you can be forced to stop work, obtain a permit, come to court and pay fines, etc. If you are building within setback or buffer limits, you can be forced to dismantle your entire job. Permits require site plans, which show that the building is being built in a legal spot. The permit process will also enable you to ensure that you are not violating any zoning requirements, such as which way the doors face in relation to the street. I can assure you that you do not want to learn halfway into the project that you are violating multiple zoning and permiting laws.
On top of all that, if you perform structural, electrical and plumbing work without permits or inspections, you subject yourself to potential claims of anyone who might be hurt by your work. Also, ask your homeowner's insurance company if it will insure your project after completion with no permits or inspections. If you don't ask, and it burns, taking your house with it, you might be faced with a denial of coverage claim.

Finally, when you sell, most lenders will require that you swear that all improvements to the property were installed in conformance with all laws, including zoning and permitting.

This is just a no-brainer for me. In my private law practice, I would never advise a client to do this work without permits and inspections.

 

[Randy_Myers]

Michael,

I've been a building contractor for 40 years and recently built a 3000 sf shop with a loft office above the garage portion of the building - I'm a woodworker as well as a restorer. My plans were drawn by an architect and engineered per county requirements. I used TJI pro-350 16" trusses -16" o.c.to span a 28' width. My office floor feels solid and there is a lot of stuff up here.

I'd also like to suggest that you consider putting tubing in the concrete slab and below the plywood decking on the loft floor for an in-floor heating system. Mine is fired by a tankless water heater located in the room that has my compressor and parts storage and it provides both domestic hot water and (on a seperate circuit) hot water to heat the floor. Because radiant heat heats objects instead of air, your car and tools are warm as well. My system has worked flawlessly for 4 years. I don't run it all winter, I turn it on on Friday and turn it off on Sunday evening if I don't think I'll get back in during the week. Best money I've spent on a building.

I second the judge's advice to get a permit and the general feeling that an engineer is worth spending money on.

Good luck,

Randy Myers
Santa Rosa, CA