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-   -   Building deck on side of Gambrel style roof - questions (http://www.diychatroom.com/f19/building-deck-side-gambrel-style-roof-questions-103948/)

sheslostcontrol 05-09-2011 07:55 AM

Building deck on side of Gambrel style roof - questions
 
I have a two-story detached garage/office with the office area tucked inside the gambrel roof. The south side of the building runs parallel to the ridge vent and this side faces a garden and some woods - great view. I'd like to install a deck to enjoy it more.

The thought is to remove a 24' wide section (32' total width), add a 10' x 24' deck, build a roof over the deck, and tie the deck roof into the existing gambrel roof.

Before I rush into anything, do any of you foresee potential pitfalls with cutting out a section of the side of a gambrel roof to make room for a deck?

Here is a very rough sketch of the west side of the garage (measurements are not exact).
http://i162.photobucket.com/albums/t...OUTH_VIEWa.jpg

Here are photos of the inside of the attic area:
http://i162.photobucket.com/albums/t...s/SANY0055.jpg

http://i162.photobucket.com/albums/t...s/SANY0053.jpg

http://i162.photobucket.com/albums/t...s/SANY0057.jpg

http://i162.photobucket.com/albums/t...SANY0060-1.jpg

Here are some ideas of how this new deck might look:
http://i162.photobucket.com/albums/t.../SANY0017a.jpg

http://i162.photobucket.com/albums/t...2pdf-pages.jpg

http://i162.photobucket.com/albums/t...elroofcopy.jpg

Look forward to any comments or suggestions.

Ron6519 05-09-2011 03:28 PM

Is the roof of this deck a traditional joist sysyem with sheathing and fiberglass roofing?
What are planned for the walls of the deck?
Ron

sheslostcontrol 05-09-2011 05:27 PM

The roof will be made of 2x6 rafters over 2x10 joists. Plan on laying down the same shingles I have now, wiht felt paper over radiant barrier. I will put some R-30 in the joist pockets.

The walls (which are 36" high knee walls, with screen above that. Walls will be 2x4.

The deck posts will be 6x6 set in 12x12x24 footers. According to the inspector I have to float the deck, so I'll have 4 posts on each side (8 total).

sixeightten 05-09-2011 05:37 PM

Not sure why the inspector would tell you that. I think if you hooked up with a decent engineer, this could end up exactly like you want.

sheslostcontrol 05-09-2011 08:31 PM

GIven this is a DIY forum, am I going to wind up paying as much to an engineer for plans as I would for the labor or materials? What is wrong with floating the deck? If it is the same height, and buts up to the building and has a roof over it?

sixeightten 05-09-2011 08:36 PM

Quote:

Originally Posted by sheslostcontrol (Post 644748)
GIven this is a DIY forum, am I going to wind up paying as much to an engineer for plans as I would for the labor or materials? What is wrong with floating the deck? If it is the same height, and buts up to the building and has a roof over it?

Many building departments will want you to have some approved plans for a project like this anyway. I don't think there is anything wrong with a floating deck. I prefer the deck that you proposed however. Fewer posts will look better in my opinion.

sheslostcontrol 05-09-2011 09:37 PM

Am I wrong to freak out about the prospects of having to pay 500-1000 to an engineer to draw plans? This kills the project. They did not require plans like you described when the garage was built last year -- I drew them up on my computer, and submitted to the city inspector.. no problem.

Robo_geek 05-09-2011 11:56 PM

Quote:

Originally Posted by sheslostcontrol (Post 644748)
GIven this is a DIY forum, am I going to wind up paying as much to an engineer for plans as I would for the labor or materials? What is wrong with floating the deck? If it is the same height, and buts up to the building and has a roof over it?

I'm no structural engineer, but the combined mass of the deck and the roof above it is quite a lot. Unless the side wall of the structure is framed really well, it's loading that side of the structure a lot. Therefore the most conservative approach is to add more structure, e.g. floating the deck.

While your structure looks very solidly built, often you see wimpy 2x4 framed walls and undersized footers on this type of structure. Adding a deck to such a structure could at best, cause it to rack,and typically cause it to sag.

sheslostcontrol 05-10-2011 06:15 AM

The lower walls are 2x6, 16 on center. The floor/ceiling joists are engineered OSB I-beams. I first thought I could just lay down deck floor joists on top of the existing 2x6 exterior wall. Inspector nixed that via phone. I thought the 2x6 wall would have been plenty strong enough, but I assume he knows his business better than I.

Ron6519 05-10-2011 07:10 AM

Quote:

Originally Posted by sheslostcontrol (Post 644907)
The lower walls are 2x6, 16 on center. The floor/ceiling joists are engineered OSB I-beams. I first thought I could just lay down deck floor joists on top of the existing 2x6 exterior wall. Inspector nixed that via phone. I thought the 2x6 wall would have been plenty strong enough, but I assume he knows his business better than I.

The ceiling joists in the picture look like dimensional lumber. If the floor joists are the I beams, the rim joists would be what material? I don't think the typical engineered rim joist wouldn't support a ledger for the deck.
Work up a plan like you did for the garage. If it's not approved, modify it until it is.
Ron

sheslostcontrol 05-10-2011 10:08 AM

Quote:

Originally Posted by Ron6519 (Post 644923)
The ceiling joists in the picture look like dimensional lumber. If the floor joists are the I beams, the rim joists would be what material? I don't think the typical engineered rim joist wouldn't support a ledger for the deck.
Ron

Right -- the pictures are of the garage attic, over the upstairs. I guess I called them the wrong thing.. the floor joists between the shop & upstairs are the engineered I beams. The ends of the i-beams look like OSB. I thought I could cut out sections and rest the deck joists on the 2x6 wall, but considering the weight of the deck and roof -- it makes sense to fully support the deck with posts set in footers.

Ron6519 05-10-2011 11:28 AM

Quote:

Originally Posted by sheslostcontrol (Post 644989)
Right -- the pictures are of the garage attic, over the upstairs. I guess I called them the wrong thing.. the floor joists between the shop & upstairs are the engineered I beams. The ends of the i-beams look like OSB. I thought I could cut out sections and rest the deck joists on the 2x6 wall, but considering the weight of the deck and roof -- it makes sense to fully support the deck with posts set in footers.

What sort of footing do you have under the garage that the building inspector wouldn't allow the deck joists to rest on the top plate of the wall?
Most of the weight would seem to be on the posted edge of the deck, not the wall.
Ron

sheslostcontrol 05-10-2011 12:02 PM

Quote:

Originally Posted by Ron6519 (Post 645028)
What sort of footing do you have under the garage that the building inspector wouldn't allow the deck joists to rest on the top plate of the wall?
Most of the weight would seem to be on the posted edge of the deck, not the wall.
Ron

Poured slab with rebar reinforcement. I think the edges of the building are at least 12" deep (live in Georgia low frost line).

Gary in WA 05-10-2011 10:39 PM

As said, you will be changing the shear and loading of the structures side/roof with that big a hole removed. I would expect to shear wall (add inside sheathing) of the last 4' at each side of the opening. A header would need to be spec'ed out and bearing point loads on to the ceiling (strengthened)/floor engineered joists below to carry the new load. Possibly a new ridge beam, not existing board, may be needed for the low-slope new rafters unless the B.D. approves of whatever you draw. With the deck floating, I doubt the roof will be attached and structural. The ridge/ceiling joist would probably need engineering. Keep us informed…..
One of our pro Engineers should be along shortly, or a house designer.......


Gary

sheslostcontrol 05-10-2011 11:15 PM

Ok, can I get this out of the way? How much should I expect to pay to have someone (an engineer) draw up plans for this project?


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