Need Some Framing Ideas For Addition

IHI

I know I'll end up going and talking with an engineer at some point, but I want to get any other ideas from you guys too before I get to that point.
Currently a freind of mine wants to add on to his house, the story and a half is already finished upstairs with very narrow walk way in center only. He wants to add 2 dormers on the front of the house just for astheitcs and then start a new roof line just below dormers and bring it out to cover his porch. this is no biggie.

On the other side of the peak he wants to add a full length of the house dormer to make more usable space, but I and homie are'nt real keen on flat roofs, but he does'nt want to do a complete 2nd story additon either so we're back to using what we've got.

First drawing is what we're dealing with-the base house, 9' side walls and then another 9' to peak. houe is 26' wide on this side profile in pictures and is 30' on sides that face front street anbd backyard.

By adding a wall on rear dormer roof will almost be flat, my question is ridge board and the new proposed design-will it be strong enough to support the load. He has'nt decided on interior floor design yet so just figuring open interior for now, and common sense says nothing there to structurally to support center ridge board. Drawing #2 is what he wants to do so you get a better idea of what I'm talking about. We'll have to figure some interior layout to help support center ridge beam, or even better remove it all together and get a big glue lam or some other beam to put in it's place.


This other design he thought about building stright up from peak and installing transom windows, mainly to allow enough build up height to get the needed slope for installing shingles on new roof instead of using rubber membrane. I know with this design we'd defiantely have to have it drawn and stamped by engineer since once again there is no real support in the center.


This 3rd design is my favorite of the ones I submitted since profile is much better than that in the 2nd photo and I'm trying to push for a pleasing exterior as well as useful interior space since I dont want to add a typical hacked up looking addition. He's all for it pending budget. We tried to push for a completely new second level but he does'nt want to go for the additional walls, trusses, etc..even though it'd really expand the 2nd floor usable space since IMO these drawings are just bandaid designs and will not really open much space up other than the one side of the room.

So guess I'm looking for thought/ideas on if standard framing practices would be possbile for the 1st proposed idea or if it's a definate must for engineer design/stamping? Or is there some tricks you guys have done that would make this feasable. Currently the roof span on flat roofed area is 16' so jacking around the current roof line(peak) in order to keep 8' clear ceiling height is a must IMO since ceiling joist/rafter will have to be sizable to hold load even if we go 12"oc.

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redwing510

Looks to me like your almost putting close to a second floor system down now with one half the house on the back side needing a floor plus the floor in your two dormers depending on the width of those. First, is there a load bearing wall on the first floor to support the second story floor? If not that needs to be addressed. Also why not run the two dormers out flush to the front walls of the house? Another thought, continue the roof line coming from the front to a point where it would meet the same pitch roof line coming off the back wall which would bring your ridge line off center towards the back of the house which could be done with a ridge beam (laminate). As long as you have solid support from your foundation up to your beam. Don't know if any of this helps, but I did a couple of years in pre-architecture in college and have design and built a few homes of my own. i'm old school, I still use paper and pencil for my prints, no compter.

IHI

Homie has homes on either side with small dormers stuck in the middle of the front roof and he did'nt like the looks of them and wants new dormer ridge to meet existing house ridge. The picture is decieveing but there would only be 4' from end of new front dormer and front exterior wall-mainly so you could at least walk into the dormers and look out-but still have a 2'8" area below the window in dormer for built in toy boxes/seating area.

Rear dormer HAS to be at least as tall as existing ridge for ceiling height, any lower and a 6' man will bump his head. Currently attic is typical A design with 8' clear in center only, move 1-2' left or right and you smack your head on the wood ceiling in place currently.

The home is 26' wide and has a load bearing wall right down the center full length of the house with beam in basement supporting that load as well into the foundation. 1st floor has 2x10 16"oc floor joists, 2nd floor(attic space) has 2x8's 16" oc and are resting on the center bearing wall underneath.

Currently the attic space is 100% completed, beent that way for as long as he's owned the home, but he's wanting to revamp it and open it up. Here's the trick, he does'nt really want to pay a engineer to come out and approve/draw up plans, but I keep telling him for safety this is the only way I can think of doing it right to be sure the house structure can hold everything-especially once I come up with some deisgn of roof support for center as interior wall layouts are yet to be determined.

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A+Carpenter

No it's more like 1-2 left or right and you will smack your head on a nice ring shank or galvie

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karma_carpentry

Glad you started out by saying you're going to have to consult and engineer.

As for the full length shed dormer... once you deconstruct any section of a gable roof system, you have to support the ridge board and convert it to a ridge beam that bears all the rafters on both sides.

What is your ridge board by the way? It's not likely it's up to par for its new job. In a gable roof, the ridge board is just a place-holder for the rafters, not a support. Once you change it to a shed dormer, you've got two back-to-back shed roofs, because you've destroyed the triangle of the rafters and attic floor joists.

So your engineer will need to figure the load of the rafters on both sides of the ridge and you'll need to sister on enough load-bearing capacity in the form of 2x or LVL (and maybe a flitch plate if you really want a long open span with no columns) and you'll also have to be sure there's adequate bearing for the new load points down to the footing, as redwing pointed out.

I think that once you decide on a full-length dormer, you've passed the point where it really makes economic sense to save the other side, unless it's a matter of zoning and clearance with the local authorities, etc.

But for a caveat, I don't have all the experience to back this up. I've added smaller dormers but never a full-length dormer on a house. So take my words with a grain of salt.

Let us know what design you settle on, and what the considerations were in that choice.

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