Victoria Cottage - adding a dormer

[NavyDave]

I've been trying to finalize plans on my Victoria cottage for a few months now and will start my framing in March. I am using the alternative method using 2x8 rafters 24"OC and 2x6 rafter ties. My snow load in Tennessee where i'm building is 10PSF.



This is a rendering of how I want my design to look and my question is this. Is there any concerns that I might consider with the 2 major changes that i've made to the plans.

1. the dormer

2. changing the slope of the kitchen addition from 12-12 to 3-12 and extending that slope over the front deck.

Any input is appreciated.

[Bob S.]

We love pictures at Country Plans. Do you have any of your building site? Can you share your floor plan with us? Welcome

[John Raabe]

I like your design ideas with the deck and dormer. It is an attractive option.

You will want to have this reviewed locally both for the changes you propose and the use of the rafter framing to replace the ridge beam. Not all places allow that more traditional framing option. You can work with a local home designer and perhaps have a review with an engineer to make sure you are sizing things properly.

[Don_P]

I agree with John, an engineer needs to review your plans. It depends on the framing. If the dormer sits on the roof as opposed to the second floor, with the framing you are talking about the weight of the dormer is then being added to the load being resisted by the rafters and walls. With the raised kneewalls this area is already outside of what engineers have told me they are comfortable with. If the dormer walls run to the floor, or more importantly if there is a wall or beam under the ridge, a wall or beam downstairs under that, and support to ground under that, then it is very strong.

The 12/12 rafters would run down to the wall plate and the 3/12 (raise that pitch if you can) is overframed onto the 12/12 pitch. If I'm misunderstanding and you want to make a visible 3/12 pitch break inside and move the bearing of the 12/12 roof inboard of the exterior wall, that'll take a massive beam.

[NavyDave]

HAPPY NEW YEAR! 

Bob here is another pic as the house would be seen from the Southwest. Also there's a pic of a possible FUTURE "Library/Office" addition. I started a thread in the Owner-Builder section labeled "Victoria Cottage NE TN" There are several pics of the building site on there and also there is a floorplan but it doesn't have the dormer. That's still under consideration as you can see.




John, I do plan on having an engineer give me a warm and fuzzy before I decide to "undersize" things. I actually may go with 2x10's for my rafters so I can over insulate and have a little more space for venting as well. As far as codes go, there aren't any where I will be building. It's an unincorporated town and the only inspections I'll incur (other than a septic permit) is a rough electrical and a final electrical. That's one reason we like the area so well.

Don, My plan is to definitely have the bottom portion of the dormer resting on the 6x12 beam that will span the kitchen addition. I couldn't imagine having the roof support all of that weight, i'm sure it's been done but it doesn't seem stable enough for me. Now for the pitch transition, i'm a little unclear on what you were saying. Did you mean that if I ran the12/12 pitched roof rafters down to the load bearing beam and then tied the 3/12 pitched kitchen addition roof/deck roof into the 12/12 rafter that is rested on that beam that this seems like a suitable idea?

I notice also that you feel my 3/12 pitch is a bit low. I'm sure that pitch will increas when i actually get to the framing portion of the build and can evaluate solar conditions and stand on the bulding site. I mentioned the 3/12 pitch because that is what "worked" best in my computer model. If I do stay with the 3/12 though I'd probably go with 16"OC vice 24".

For the sake of clarity I would not try to change where any load bearing points are with either the dormer or by starting my pitch transition anywhere other than on the load bearing beam. Is it reasonable to say this is a sound way to deviate from the plans?  Once again I do plan on bringing this up to a structural professional but don't even want to waste my time trying to plan for a deviation if there are things that would possibly weaken my structure by making these changes.

Thanks for such a quick reply, the combined knowledge and willingness to help on this site is amazing. I look forward to sharing my experience later on down the road.

[Don_P]

I think it's quite do-able, please post what the engineer comes up with. I noticed and then forgot to mention before, the foundation posts under the porch posts need to line up to avoid adding the roof load to a point in the deck rim span. Those would be one continuous post on one of mine if length allowed.

[NavyDave]

Yep I'll post what I find out. For the deck posts, that is a really great Idea to have them be one integral post. I did intend to have each post over a pillar (the software I used placed the posts in the pics) but thought i'd rest them on the actual deck. It just makes sense to incorporate your idea. The structural integrity will definitely increase and it may even be easier to build. Thanks Don!