So, can I actually build something like this?

[tfalk]

I've been browsing for days now looking at gambrel roof designs and getting nowhere... bought a copy of home designer essentials and created the design below... 18x28 garage, gambrel roof designed so it's 14' 9" at the peak to stay under a 15' max height restriction. Problem is, I've never seen any design like this so I'm wondering if it's even possible to get it approved by zoning, etc???

One of my neighbors used to be a building inspector, I think he's either an architect or some type of engineer, he's designed decks and stuff for people in the neighborhood. Before I run it by him, thought I'd see if I'm way out in right field or what... Well, I know the answer to that if I'm planning on doing most of the build myself

Roof is 10/12 on the sides, 3/12 on the top, 10 foot high walls. Ridge beams show as 2x12, rafters as 2x10, 24" o.c. Trying to not have bottom chords to leave room for a lift big enough to fit my F250 on top or under...

Fire at will commander!

 

[Jlbc212]

Nice renderings, but not so nice design. The weight of the roof will push the walls out. You need ceiling joists tied to the top of the side walls and the bottom of the rafters to prevent the side walls from pushing outward.

 

[383]

Collar ties are usually used with ridge pole construction to keep the roof from pushing the walls out. They are typically installed a third of the way from the ridge to the wall, but that will be difficult to do with only a 3/12 roof pitch.

 

[Model A Fan]

Go wider than 18' too. I have a 19' wide shop and it is not nearly big enough. I find that I don't have space for my work bench and projects and tool chest. Minimum I would want for any kind of shop would be 30' wide. If you want to work on vehicles in it, make it at least a two car garage. Anything smaller is going to be inadequate and frustrating. Sure there are people who can and do use them, but given the opportunity, I wouldn't want to. My garage is 19'x21' and it is frustrating.

 

[Homerr]

The only way I see this working is some steel frames in lieu of the rafters, say at 8' o.c., with purlins in-between the frames. The frames would essentially act as the collar tie in addition to being the 'rafter'. But the shape inside and out would be the same as you have it.

 

[LXCam]

My lift and car work area is 18 X 40. Like A Fan said, it's not wide enough. Also even at a peak of 14ft, not near tall enough for a truck on a lift to walk under and work. Mine is 13' 6" clear and I can only pull off low profile cars and run the lift at full height. As for the design, that's gonna be a tuff one to pull off without additional ties which will lower you're overall interior space. Good luck.

 

[MushCreek]

If you don't want ceiling joists, go to barnplans.com and study the pictures. I used their plans for my 28 X 48, and I like their system. The plans were cheap (~$200) and the local inspector was fine with the design. They have all sorts of sizes.

 

[Matt M PA]

I'm working on some videos now for Stoltzfus Structures. They built my garage and shed. Considering how reasonable the buildings were...and the beautiful build quality...I can't imagine building my own. www.mysheds.com

 

[bczygan]

Your structure is possible, but sizing of members and connections are critical, and must be calculated.

First, if you need the vaulted and open ceiling for a lift, you don't need it for the entire 28' length of the garage. Shorten the vaulted area and you lessen the length that the beams must span and the loads they must carry. The areas in the front and back of the vaulted area can be storage trusses and become storage lofts.

The ridge beam at the peak, as you show it, not only spans the entire 28', but also bears on the headers over the doors. Those headers must be sized to transfer these loads.

The secret to gambrel roof construction is in the selection of the size and species of the members, and even more importantly, the connections between the members. What you are creating is a rigid arched truss out of solid members. The triangulation is in the members and loads must transfer through the joints and connections.

When this is properly done, then the ridge does not need to be a load supporting beam, but can just be a board for alignment. The beams you show at the midpoints on each side become unnecessary.

Actually, a combination of methods can do what you want.

The middle of the garage, with the high bay area can be open with a ridge beam bearing on doubled trusses on each end.

What is the length of the longest vehicle that you will lift? What are the dimensions of the clear area you need, width,length and height?

Bill

 

[tfalk]

Thanks guys, good info... thought something didn't make sense with the design.

Longest vehicle is a 21 foot long crew cab long bed F250. Yeah, I know bigger would be better, this is what will fit where I need to put it. I need 15 feet to the side of the property and the house is 43 feet from the side, 18 wide would give me enough room to keep the enclosed trailer on the one side and a 10 foot gap to the house. I've been living in a 19 foot deep 20 wide garage up until now, this will allow me to get a vehicle inside, close the doors and work on it. Probably going to delete the back wall door which will help from a load carrying perspective.

I think I'm going to look into the gambrel roof storage truss setup. If I add 2 beams crossing the narrower width, I should be able to box out and in effect create a vaulted ceiling area where the top of the truck could fit.

Going to go out later and measure the top of the cab on the truck, that's basically the area I need to get as high as possible.

 

[bczygan]

Thanks guys, good info... thought something didn't make sense with the design.

Longest vehicle is a 21 foot long crew cab long bed F250. Yeah, I know bigger would be better, this is what will fit where I need to put it. I need 15 feet to the side of the property and the house is 43 feet from the side, 18 wide would give me enough room to keep the enclosed trailer on the one side and a 10 foot gap to the house. I've been living in a 19 foot deep 20 wide garage up until now, this will allow me to get a vehicle inside, close the doors and work on it. Probably going to delete the back wall door which will help from a load carrying perspective.

I think I'm going to look into the gambrel roof storage truss setup. If I add 2 beams crossing the narrower width, I should be able to box out and in effect create a vaulted ceiling area where the top of the truck could fit.

Going to go out later and measure the top of the cab on the truck, that's basically the area I need to get as high as possible.

Attach to the house with a breezeway and you can widen it, and then are only limited to the house height restriction.

 

[tfalk]

Attach to the house with a breezeway and you can widen it, and then are only limited to the house height restriction.

Understand, not really a viable option but thanks for the thought!

 

[sublimate]

I had almost the same space as you.
I connected to the house with a short breezeway that tied into the basement. That allowed me to go higher and closer to the house so I could do 24' wide, but still keep the windows on that side of the house.
You don't have to share a common wall to be "attached".
Also, you shouldn't need 15' just to store a trailer. 10' wide could work.

 

[87jeepwrangler]

Collar ties are usually used with ridge pole construction to keep the roof from pushing the walls out. They are typically installed a third of the way from the ridge to the wall, but that will be difficult to do with only a 3/12 roof pitch.

there is some mis-information in this post.

collar ties are NOT used to keep walls from pushing out, rafter ties (often used as ceiling joists) are used to keep walls from pushing out.

collar ties should be located in the upper 1/3 of the rafter, nearest the ridge beam.

rafter ties should be in the lowest 1/3 of the rafter, nearest the top of the walls.

a rafter tie keeps the walls from pushing out, and the ridge from sagging.

a collar tie is resists rafter separation from the ridge beam caused by wind uplift or other upward forces.

as was explained by bczygan, gambrel roofs do not use rafter ties, and instead rely on the member sizing and connection strengths to support the loads. thus the sizes, spans, and connection types must be design and engineered by someone, not just guessed at.

 

[Jlbc212]

If the size and location is your only option and cost isn't a concern, you could build it by placing a girder along the top ridge and two more along the two sides where the roof pitch angle changes. You won't be able to shorten the 28' span too much if you plan on lifting an F250 in the garage. Even if you got the span of the girders down to 20' (a standard F250 pickup is just over 19'), the girders will have to be hefty for that span and you will need some large cross beams to support the point loads of the girders. Steel wide flange girders may be an option and cost less than built-up LVLs. You should consult with a structural engineer.

 

[Charles (in GA)]

Make sure you understand what defines max height. In many locations, it is not the highest point of the building but rather some arbitrary point say 2/3 of the way from the eave to the peak. Also, some measure the base at some unusual point, not just the surface of the slab. Know what they use for measuring criteria, it might be to your advantage.

 

[Elginz]

Trusses

 

[kbs2244]

What you have designed is a ridge beam roof.
As opposed to a ridge board.
You have 3 beams supported at the ends and your rafters rest on them in tension, not compression.
No joists or collar ties needed since the rafters are actually pulling on the walls, not pushing.

But 28 feet is pretty long for an unsupported beam.
Lacking a mid-length post, you could go with a heavy joist from wall to wall that would support a vertical post from it up to the ridge beam.
(They are called “King Posts.”)
Or you would have to go steel for the beams. and that would get heavy for installation.

In your case I would look into something like this

http://www.discountmetalroofing.com/

Note that they do have a tie bar acting like a joist at the eve.
But you can space the truss far enough apart to be able fot fit you cap between them.

 

[Jlbc212]

What you have designed is a ridge beam roof.
As opposed to a ridge board.
You have 3 beams supported at the ends and your rafters rest on them in tension, not compression.
No joists or collar ties needed since the rafters are actually pulling on the walls, not pushing.

But 28 feet is pretty long for an unsupported beam.
Lacking a mid-length post, you could go with a heavy joist from wall to wall that would support a vertical post from it up to the ridge beam.
(They are called “King Posts.”)
Or you would have to go steel for the beams. and that would get heavy for installation.

In your case I would look into something like this

http://www.discountmetalroofing.com/

Note that they do have a tie bar acting like a joist at the eve.
But you can space the truss far enough apart to be able fot fit you cap between them.

^^^ this is a good option as shown in the picture, a light weight, steel frame structure. If you want the garage to match the house, you can side the steel structure with just about any material.

 

[Bib Overalls]

If 18' is your outside width you will have, at best, 17' width inside. F-250 is 6'8" wide (without dualies). That gives you 5'2" on each side. May sound like enough but it ain't. Any chance you could get a variance to build closer to the property line? 24' is about the minimum for an efficient working garage.