New 24’x34’ Detached Garage with Attic Trusses

[sd171]

For those who are just starting this thread, here are some photos of the new garage as of August 2015:

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And now back to the original thread...

After suffering through eleven South Dakota winters with our unheated, not quite 2-car garage, we finally committed to replacing it with a new structure. It took us so long because the only way to build a legitimate 2-car garage on the property would be to tear up a good portion of the backyard and replace the driveway.

The old garage was built in 1936, and it certainly shows its age. It is slab on grade with a stucco finish to match the house and a heavy wooden 15’ x 7’ garage door. The exterior dimensions are approximately 17’ wide x 22’ deep. A few days ago, one of the garage door springs broke when my daughter was opening the door to get her bike. Fortunately it broke when the door was just starting to rise and not when she was near it. The opener continued to pull and made a terrible racket while failing to lift the door. By the time I was able to turn off the circuit breaker, the motor was fried. Unfortunately my wife’s car was trapped inside the garage, but I managed to raise the door using a Hi-Lift jack.

I’ve been thinking about this project for years, and this forum has been extremely helpful. Thanks to everyone who has spent so much time documenting their projects. Hopefully documenting my project as it progresses will help someone else accomplish their vision and I can benefit from feedback along the way.

As of today, the old garage is still in place and I am eagerly awaiting demolition.

Broken 78 year-old spring:
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Immobile garage door:
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Mostly empty interior:
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[sd171]

Over the past few years I have worked through a variety of designs to accomplish as many of my priorities as possible without the garage taking up too much square footage in the backyard or growing so tall that it overwhelms our small urban lot. These were my priorities:

1. Fit two cars for daily use with plenty of room to swing car doors open.
2. 8’ high garage door to accommodate a tall SUV with a ski box.
3. Enough space to store a third car for occasional use.
4. Enough room to get bikes/mower/snowblower into and out of garage without moving cars.
5. Storage for seasonal tires, gardening tools and general household tools.
6. Insulated and heated.
7. Running water and floor drain for washing cars indoors.
8. Attic space for use as home office or art studio (critical for obtaining my wife’s approval of the project).

By far the most difficult priority to achieve was room for a third car. I considered various car lift types and configurations, but achieving the car lift ceiling height requirements while maintaining a decent sized attic space always caused the overall building to grow too large. In the end, I decided that I could live with a third car turned perpendicular to the others and pushed against the back wall using GoJak or similar dollies. As much as I would love to have a car lift, I’m afraid my wife doesn’t share my fascination with mechanical devices and would find it unsightly and difficult to maneuver around.

I used Excel to help visualize different garage layouts. By setting the cell width = 2.00 and the cell height = 15.00, the result is decent electronic graph paper. The Border, Fill and Line tools can then be used to create simple plan views. When I had a plan view that I wanted to visualize in 3-D, I used Sketch-Up to create a simple model.

One of the benefits of a long planning process is that by the time I started talking to contractors I knew exactly what I wanted. This made it easy for them to visualize the project and allowed me to interview more contractors than I would have been able to had I depended on them to design the project. We spoke with six contractors early this spring, all of whom were recommended by people we know. The economy must be picking up because four of them were already booked until next spring. We chose our contractor last week and expect the project to get started in May. We are still interviewing landscapers.

Here are the documents I gave to our contractor to help him estimate the job. There is still time to make changes, so if anyone has feedback I would be glad to hear it.

Site plan (new garage shown in red):
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Notes for contractor:
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Excel views:
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SketchUp:
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[sean Buick 76]

Great documentation of your build plans!!!

Well the good news is that a broken spring led you to getting a new garage! Sometimes it is after an incident that our dreams come true!

 

[GRN96WS6]

I had the original wooden 16' door on my house when i bought it and the spring broke, there was no way i could open the door alone.

 

[iajonesy]

It appears to me you have left way too much back yard. You will have to mow all of that,you know. Just kidding,looks like a good workable plan. Good luck.

Mike

 

[ADSR]

Sub'd

 

[1940_dodge]

What part of South Dakota? I'm currently repping the tropical southwest side of the state.

 

[sd171]

Here is the engineering report for the attic trusses. It looks like I’ll have 7’ of headroom for about 3’ of horizontal space, which sounds a little claustrophobic. Increasing the pitch from 9/12 or moving the bottom chord down would improve the situation, but then the structure starts getting too big again. Hopefully the four skylights will make a difference.

We’ll have to trim the 2’ wide eaves, which would push the garage further from the property line than I would like. City code allows exterior walls to be 2’ from the property line, but the eaves and gutters may only extend 4” from there.

EDIT: This was not the truss design I ended up using. I special ordered this design with an additional 1' of height added by moving the bottom chord down.

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[Gentle_Ben]

We’ll have to trim the 2’ wide eaves, which would push the garage further from the property line than I would like. City code allows exterior walls to be 2’ from the property line, but the eaves and gutters may only extend 4” from there.

Are you 100% sure on that? I deal with building codes all the time and the rules for eaves on detached structures are usually (but not always) 1ft from the property line. The 4" should apply only to gutters. Might be worth double checking, 2ft wide eaves are nice.

Good luck with the build, plans look great!

 

[Stuart in MN]

My garage is 24 x 40, with 10/12 attic trusses. There's a photo of the attic space in this post: http://www.garagejournal.com/forum/showthread.php?p=1886549&highlight=attic#post1886549 This was during construction so I didn't have the floor put down yet, but it will give you a visual on how much space is available up there. What's the pitch of your house roof? Personally, I'd try to match the house and garage, I think it will look better.

 

[sd171]

Are you 100% sure on that? I deal with building codes all the time and the rules for eaves on detached structures are usually (but not always) 1ft from the property line. The 4" should apply only to gutters. Might be worth double checking, 2ft wide eaves are nice.

Ben - thanks for bringing this to my attention. I talked to the planning department months ago and thought I understood what they were saying, but called them again today just to make sure.

The planning department rep said that walls may be as close as 2' from the property line and that eaves and/or gutters may extend 4" beyond that, but he wasn't sure. So he transferred me to the building department.

The building department rep pulled out his codebook and said that if a detached garage wall is located 2' from the property line, the eaves may project 4" from the wall and gutters may extend further. He said gutters weren't in his codebook and could be put on at my discretion. In any case, everything within 3' of the property line must be sheetrocked inside and outside for fire protection.

He said that I have to play by two rulebooks - the planning department, who determines where structures can be located and the building department who determines how structures must be built. In this case, apparently the two departments don't agree on the rules.

 

[sd171]

What's the pitch of your house roof? Personally, I'd try to match the house and garage, I think it will look better.

Stuart - Thanks for the photo of the 10/12 attic trusses with 24' span. That looks less claustrophobic than I thought, though my attic would be smaller with a 9/12 pitch.

I agree with you that matching the pitch of the house would be ideal, but the house pitch is the same as the old garage which appears to be about 7/12. Fortunately, there isn't really a vantage point where you can see the house pitch and the new garage pitch face-on at the same time, so I'm hoping a 9/12 pitch won't look odd. I don't want to go any steeper just in case I'm wrong and to keep the overall height down, but at 24' wide, a 9/12 pitch is as flat as you can go in an attic truss and still have 7' of headroom down the center.

Here is a resource I found online to help estimate the size of the attic space. It turned out to be an exact match with my local truss supplier.
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[Xander]

I like where this thread is going!!! Plans look great.

X...

 

[madoc1]

great planning. I think there must be a misprint on the 10/12- 24w. line of the last chart. the h-2 dimension seems too tall to me. 7-7-13? not that it matters in your case.

 

[sd171]

I think there must be a misprint on the 10/12- 24w. line of the last chart. the h-2 dimension seems too tall to me. 7-7-13?

Good catch - I updated the post above to highlight the error.

 

[sd171]

The demolition of the old garage is now complete. I was surprised that my contractor removed the structure with only power and hand tools.

Step 1: remove the garage door

Step 2: cut away the roof in between the rafters
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Step 3: brace the walls, then cut down the rafters

Step 4: knock down the walls with a sledgehammer
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They finally called in the heavy equipment to remove the old concrete slab.
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[captain14]

I will follow this thread to see the good construction on the new garage

 

[sd171]

So let's say you're a landscaper who is building a fire pit. The boss says it has to have a 3' deep frost footing. You start digging the hole only to discover power, cable and telephone lines buried 2' deep. After you've finished your beer and considered the options, do you:

A) Settle for a 2' deep footing. After all, it's only a fire pit.

B) Pretend you didn't see the utilities. Dig past them until you reach 3' and then fill the hole with concrete, encasing the utilities for eternity. Who's going to know?

May I present option B, which is sitting precisely where the new garage footer needs to go:
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Now we wait for the utility companies to re-route their cables before we can finish the excavation.

 

[sd171]

We were making such great progress, and then everything came to a halt for a while. Both the power and cable TV companies were reluctant to splice lines underground, but eventually they were convinced that this would be OK as long as we replace the entire lines between the pole and the house when construction is complete. I figured as long as we have to replace everything, we would upgrade to 200A service. (Edit: actually, it turns out we already had 200A service due to the previous owner's remodel and both services eventually agreed to splice underground.)

So after a couple of weeks waiting for the utilities to splice temporary lines (Edit: which became the permanent lines by the end of the project), we finally removed the old fire pit footer (the hole in the lower left corner of the image) and finished the excavation. At that point, it started to rain...

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And it continued to rain almost every day for about a month.

 

[sd171]

Last week it finally dried out enough to start pouring footers. The concrete sub wanted to use a pump truck to reach the back wall, but the trees in our neighborhood are too large for the boom to clear the house and the driveway is too tight to extend the truck's outriggers.

Their number one priority seemed to be avoiding the use of wheelbarrows, so instead they filled in the front wall excavation so they could drive the mixer into the center of the garage. What would have been two pours is now four pours plus fill and another excavation. But at least nobody had to push a wheelbarrow, right?

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[sd171]

One of the reasons we waited so long to replace our old garage was knowing that we would have to essentially destroy our backyard in the process. We enjoyed our old wood burning fire pit, but it had to be removed to make room for the new garage. We came up with this design for a gas fire pit to replace it (EDIT: we removed the first step in the final design to reduce the overall height):

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Of course that means another round of excavation, and now our entire backyard is either a hole or a dirt pile.

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[sd171]

Foundation is complete. Lines for water (black) and sewer (white) run underneath footers and driveway, then through basement wall of house to stay below frost line.

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[sd171]

Progress after Day 2 of framing:

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We decided to use 2x6 framing for the additional insulation and strength. We also modified the truss design to increase headroom in the attic by moving the bottom chord down. According to the new truss design sheet, unfinished headroom has increased from 7' to 8'. I was afraid this might make the garage appear too tall for the lot, but so far I'm happy with the scale. The extra 1' of headroom will make the space feel less claustrophobic.

EDIT: In case the image below is unclear, the overall height from the bottom of the bottom chord to the top of the peak is 11'. So with a ground floor ceiling height of 9', the total height of the garage should be about 20' (I haven't measured this myself).

EDIT2: The finished dimensions of the attic (after drywall and trim) are:
Ceiling height (center): 8'
Short Wall Height: 4'-1.5"
Floor Width: 13'-10"
Width of 8' ceiling: 3'-9"
Unwalkable area for 6'-2" adult while standing: 3' on each side (i.e. a 6'-2" adult will hit their head on the ceiling if they walk closer than 3' from the short walls)

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[Ihateclevernames]

Looking good! I am really digging the attic trusses. Great place to store all of the extras!

Or the mother in law........

 

[sd171]

More framing progress:

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The garage door opening is actually larger than it appears because the OSB hasn't been trimmed back yet. You can see the actual framed width showing at the bottom of the OSB.

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The ladder in these photos is 5'-8" tall. The window opening is 4' tall x 5' wide. The bottom of the window header is 6'-10" from the floor. The bottom of the window opening is hidden by the safety railing.

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The attic is surprisingly roomy. I am very glad that we changed the truss design to achieve 8' ceiling height. We had the builder lay plywood flooring between the attic walls and the eaves in case we ever open up those walls to add storage inside the trusses.

EDIT: It turns out that this was a great idea. We use one side for storage and the other side for HVAC and low voltage wiring.

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The staircase dimensions are pretty tight. We made the lower landing as high as we could while maintaining reasonable headroom between the lower landing and joist of the first truss from the wall (this truss is doubled because one truss was skipped to allow for the staircase). Even so, we were not able to place the top landing in the middle of the attic without increasing the stair rise. The skinny legs of the ladder in this photo are placed approximately where the staircase will end (the plywood floor will be trimmed back). There is just enough headroom here, but we don't have much room to spare.

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[sd171]

OSB trimmed to show actual dimensions of openings. Skylights, cedar fascia and aluminum soffits installed.
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Vapor barrier and rebar in place.
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Concrete floor poured, power troweled and expansion joints cut. Drain is in center of floor to minimize slope. Sump with P trap (required by city), vent and water connections are positioned underneath stairs.
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[kyle@hcb]

Might have to copy your firepit idea lol. Nice work!

 

[sd171]

Stairs are in.

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Stair measurements:
16 steps total including the lower landing as a step and counting the final step onto the attic floor
8" rise and 11" run for each step (not including overhang of tread)
31" vertical from concrete floor to top of lower landing
124-1/4" vertical from concrete floor to top of attic floor
83" headroom from lower landing to bottom of floor joist
83" headroom (approximately) when standing at top of stairs in attic
41" stair width not including knee wall (i.e. stair treads are 41" wide)

I'm not happy with the length of the wall underneath the steps, so I've asked the builder to remove part of the wall. The wall is 43-1/2” long, which leaves 183" horizontal clearance to the far wall. Since one of my goals for this garage was to be able to fit a car parked perpendicular against the back wall, I would like to have as much horizontal clearance as possible. I hope to shorten this wall to not much more than 24" long to accommodate a sink. That would leave 202" horizontal clearance to the far wall and a minimum of 35" vertical clearance for a car hood at the edge of the stair wall.

The staircase has four stringers reinforced by one 2x4 on each side nailed to the outboard stringer. It seemed pretty solid even before they built the wall underneath the staircase, so I don't think shortening this wall will cause a problem.

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[sd171]

Windows, walk door and shingles installed.

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Beginning to install unpainted fiber cement siding with 5" reveal. Electrical rough in completed.

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We had the builder cut back the wall underneath the steps to 25" wide to just barely accommodate a 24" wide sink vanity plus 1" of countertop overhang. Notice the hot and cold water hose fitting under the stairs for washing cars inside in the winter. We are installing a small electric water heater instead of an instant hot water heater because the plumber said nobody is happy with instant heaters and most switch them out for small traditional heaters.

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Originally, we planned to have heating only via a natural gas unit hanging from the ceiling on the first floor and electric baseboard heaters in the attic. Eventually we talked ourselves into air conditioning as well. We considered two mini-split/PTACs on the back walls, but the HVAC contractor thought they wouldn't be powerful enough to circulate air to the garage door side of the structure. He said that positioning the attic unit on the wall above the garage door would improve circulation, but we didn't want to see a vent poking through that wall.

Instead, we decided on a traditional forced air HVAC system with electric heat and cooling. The additional plywood flooring we laid down next to the eaves proved to be useful and also made it easier to route electrical and low voltage wiring without climbing up and down ladders. While we have lost potential storage on one side of the garage due to the HVAC installation, the system is now hidden and we still have the opposite side available if we ever want to store anything behind the attic walls.

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[MacTexas]

I like what I see. Looks like you will be ready for winter with a nice warm garage and a nice warm fire pit.

 

[sd171]

I like what I see. Looks like you will be ready for winter with a nice warm garage and a nice warm fire pit.

Thanks. We're pretty excited about the warm garage in winter and cool garage in summer and hope the fire pit will increase our outdoor use in late fall and early spring. I don't think there is a fire pit in existence that would take the edge off a January or February evening in South Dakota. Maybe if we installed a hot air balloon burner and a heat reflective canopy...

 

[sd171]

Insulation is complete.

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Also showing routing of speaker and thermostat wire. Conduit is for future low voltage wiring between electronics cabinet on ground floor and attic crawl space. I think I already have everything covered, but you never know.
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[Baada]

How does 8" rise feel when you climb the stairs? Since it's its over the recommended max riser height of 7 3/4" (from everything I seem to read anyway) I'm just curious if it feels like a really big step or not?

Looks great though, I'm jealous.

 

[sd171]

How does 8" rise feel when you climb the stairs?

I don't notice that it feels steeper or has taller steps than normal. It probably helps that it's not near any other stairs, so you approach the staircase without muscle memory from the last staircase you climbed. There is also something about the approach that makes me climb the stairs slower that I normally would - maybe the lower headroom or needing to turn the corner at the landing.

The attic is classified as storage rather than living space because of the stair dimensions. In this case, code requires more clearance at the top of the staircase than we have. I believe they measure headroom 3' horizontally from the top stair, and my roof angle clips the headroom too much. We could have added a step below the landing and removed a step above the landing to get the staircase to end closer to the middle of the garage, but that would have reduced headroom at the landing unless we made the landing smaller (and the staircase narrower).

I like how this staircase turned out and wouldn't have done it differently. The key to making it fit was adding an extra 1' of height to the standard truss design.

 

[Baada]

I didn't really think it would make that much difference but to hear some people give their opinion about going over 7 3/4" riser height means you are going to need a rope and climbing harness.

I was also wondering how you got around the code....good to know as I may need to do something similar in the future.

Keep up the good work.

 

[ICT_Kevin]

Mine are almost 8" too, but the house stairs have been 7.5" since 1925. If you can tolerate the house... I still skip steps when I'm moving fast up or down. Much steeper, and I would need to slow down a bit.

Nice shop. It's about as similar to mine as any in work now. Good use of skylights.

 

[sd171]

Thanks, ICT_Kevin. I have an old house as well. The original step risers are 7.25", the remodeled area has a 7.5" riser staircase and now my garage has 8". I don't notice a difference between any of them unless I'm paying close attention.

For anyone contemplating a similar garage build with attic trusses, ICT_Kevin's project is a good comparison. If you intend to use the attic as office space (i.e. sit at a desk with a view out the window), dormers are great. It's difficult to tell from the photos, but my skylights are too high to see out of - at least horizontally. I'm 6'-2" tall, and I can barely see over the bottom sills when standing up.

We considered dormers instead of skylights, but opted for a slightly lower profile building that still has good light in the attic. If we ever want desk space in the attic, the only view is at the gable end over the garage door.

 

[sd171]

Siding is finished (but still unpainted).

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Drywall is almost finished.

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Access panels have been cut into the potential storage area and also to access the HVAC filter. I hope this unit works forever, because it would be an ugly job to replace it. I think it's assembled from 23" sections because they said it was a tight fit, but they didn't have to remove any studs during the installation.

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[sean Buick 76]

Top notch work, you should be proud!!!!

 

[miamivice]

Looks great!