Have a project to add a full shed dormer to the back of a two story colonial. The house is 26′ by 36′ so it is clear that I will need to add a structural ridge and the calculations show that the ridge will need to be supported in the center of the house as well and on the gable ends, in order to keep the span down and the beam size reasonable.
There is a center stair core with 2×4 walls in a reasonably convenient place to support the ridge beam in the center. Cutting the span down
so I only need double 16″ LVL for the ridge.
The question is what options do I have for transferring the end loads of the ridge to the basement. Do I need to:
1) open up the stairway and gable end walls and add a double or triple 2×4 column all the way to the basement(messy)
2) or can I spread the load across the top of the 2×4 wall in the attic floor maybe with a LVL header and then do the reverse down in the basement supported by a new lally column?? If this works, how do I figure out how many 16″ studs the header should span??
Replies
You probably do need to make sure you have solid blocking in your end walls all the way down to the foundation.
But the biggest load by far will be at the center bearing - That's the one you need to pay attention to the most. At LEAST half the load from the entire beam will bear at that point.
Why do you need a structural ridge, is it a cathedral ceiling the entire length of the dormer? Aren't there any perpendicular walls there like bedroom, closet, bath, hallway walls?
Here is a cross section
Red is new.
All of the existing rafters under the new red rafter will
be removed.
That's what they always look like.The rafters always come out. This is from my first post.>>Why do you need a structural ridge, is it a cathedral ceiling the entire length of the dormer? Aren't there any perpendicular walls there like bedroom, closet, bath, hallway walls?<<Joe Carola
here is the 2nd floor plan
the master does have a cathedral ceiling.Leaving that aside for a second.
Joe, I think I see where your question is coming from
looking at my own diagram I can see that the 2nd floor walls
are tied together.
So if I add a ceiling joist to my diagram from the top of the dormer wall to the front roof rafter. that is enough to hold the dormer wall from bowing out???On to the master's catherdral ceiling. looks to me like the existing structure might have issues.What does your reference to perpendicular walls mean.Thanks for the discussion.
here is how the master ceiling is framed
This cross section isn't the same as the cross section in post #4.This cross section shows no shed roof and dormer.Joe Carola
Edited 6/5/2007 9:55 am ET by Framer
sorry here it is corrected.
You forgot the floor joists.Joe Carola
In my veiws they are all there??
No there not. Look at post #4. They are there right underneath the dormer wall. Look at post #11. There not there.Your adding a wall on top of your second floor wall with a shed roof going into the existing roof and removing the ceiling joists. Your just making the dormer for the attic.You can't just throw a wall on top of the second floor wall like and remove the ceiling joists and have a cathedral in the master bedroom. That wall would have to be one wall all the way up to the shed rafters.Joe Carola
Edited 6/5/2007 5:14 pm ET by Framer
Is the missing floor joist you are talking about the one in light green in this attachment.
If so, Then I agree with I wouldn't build it this way. But everything shown in black in this drawing is the way the house was built by the orginal builder.
Your removing the existing rafters the entire length of the house right?
The Master Bedroom, is that the only Cathedral Ceiling and the rest has all the existing ceiling joists remaining?From the Master Bedroom closet/bathroom wall you will have interior rafters running from that wall to the bottom of the existing rafters?Joe Carola
probably have the shed start 2 ft in from both sides
but essentially the whole back of the house.
The master section is the only cathedral. And the
ceiling of the master closet and bath is framed with 2x8.Your diagram looks right.
You hire an engineer to do the math and spec the materials.
Why don't you take your useless advice elsewhere?
Are you always an idiot, or just when I'm around?
I have to agree, if you don't have anything to add why respond.I will probably end up hiring an engineer for final approval, but I like
to understand the solutions myself and get more educated as a do my job.
This forum has been a wonderful place to do so.Thanks to all that contribute with useful information.
<< Why don't you take your useless advice elsewhere? >>
I disagree Ron. Why so harsh? How many times have similar questions come up and everybody has said the same thing - "hire an engineer".
I don't see how any solution concocted on the forum would pass building codes without a whole lot of trouble, or a little stamp from an engineer. I understand the desire to understand how things work and how the solution might work - but hiring an engineer woudl still be a very good idea. As a contractor, it would certainly help me sleep at night, at the least.
Justin Fink - FHB Editorial
Your Friendly Neighborhood Remodelerator
Edited 6/5/2007 2:51 pm ET by JFink
My post to GHR was personal - Not a general statement.He has continually given out useless or copletely wrong engineering information. He seems to hang out on this board for no other reason than to pat himself on the back for being the wonderful engineer that he claims he is. He has never once (to the best of my knowledge) given usefuly or helpful advice to anyone on BT. When someone calls him on it he whines to the moderators. His post in this thread showed his typical smart-a$$ed attitude. There was absolutely nothing helpful about it. The OP wasn't asking for an engineering solution for a beam - He only wanted general info about how to support it.So I stand by what I said. GHR's attitude goes completely against the general helpful nature of BT.
Never turn your back on a threatened danger and try to run away from it. If you do that, you will double the danger. But if you meet it promptly and without flinching, you will reduce the danger by half. Never run away from anything. Never!" [Winston Churchill]
Position noted. I wasn't aware there was a history. but anyway, let's not derail the conversation anymore...apologies to everyone.Justin Fink - FHB Editorial
Your Friendly Neighborhood Remodelerator
Bosshog seems to have problems with people who disagree with him.His tactic appears to be to abuse them until they leave.(From his comments it appears that our hosts are not pleased with him. I suppose if he gets reported again, he will no longer have the ability to post.)----The original question was "how do I figure out how many 16" studs the header should span??"Sure sounds like an engineer is required but ...
Edited 6/5/2007 5:02 pm by GHR
He asked how one does something and your reply boiled down to "You don't. You hire someone who knows how."Typical.SamT
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