Attaching Open Gable Roof to House

[Dave72]

I'm building a deck and plan to have half of it covered with an open gable style roof. I'm looking for advice on how I can attach it to the house. At first I thought I wouldn't attach it and would just use 4 posts, but I'm unable to put posts so close to the foundation of my house as I'd have to dig 8'+ before reaching undisturbed soil.

So it seems the only option I'm left with is to attach it to the house, which really is nicer since I won't have posts getting in the way as you exit the back of the house. My concern is where the point load is going to be. My understanding was that there needs to be a point load at the end of the beams to act as sort of an internal post inside the house. Is this the case? Or can i just attach and build out wherever I see fit?

I've attached an image to better show what I'm talking about. Right now the edges of the roof structure are close to the edge of the door on one side and the window on the other side, but not quite close enough. The drawing isn't quite to scale, but if i were to move things in to the edges of the door/window the covered area would become too small.



 

[beenthere]

Welcome to the Forestry Forum.

Might be most important in your attachment to know what the framing is in your house under that siding. There will be some dead load of the roof and likely a live load. (where you live can be entered in your profile by clicking on your forum user name.... it will take you to your profile ).

[Roger Nair]

You will be dealing with point loads applied at three spots, the ridge and the two plates with the load at ridge being approximately twice than at the individual plates.  How is the house framed?  Is it platform. balloon or timber framed?  Where is the additions beam level relative to the floor level?  What is the size of the addition and the scale of the forces?  All those considerations matter.

Generally speaking, I would approach the problem with a siding tear-off, cutting out sheathing to place jacks at the bearing points.  The details govern the solution.

[Carpenter]

Your proposed scenario is really not much different than a deck with a ledger board.  Codes for a deck with a ledger board have been tightened up lately.  I believe they now call for two half inch lag bolts every two feet.  This works fine for a deck, as you are generally screwing into the rim board, or a floor joist, which is right on the foundation.  It will work just fine in your scenario as well as long as you can find the studs.  From the pictures, I don't think any drastic re-framing of your house is in order to support the load.  Half of the load that you'll be adding will be supported by the posts, and the other half can probably be absorbed by the framing that is already in place, of course I'm assuming conventional stud framing on 16" or 2' centers.  Preferably on 16" centers. 

A timber frame is only point loaded because all of the weight is carried by the posts.  If you have a ledger screwed to the house to take the weight, instead of posts, then the weight is distributed among all of the members carrying the weight, just like in conventional framing.  There will be a little more dead load to deal with, as you are using heavy beams, but your live load will be the same. 

[razor]

I was faced with the same dilemma a few years ago. My solution was to rest the sill beam at the house end on the foundation wall. I notched out a pocket in the house 2x8 rim joist for the sill timber. This left a 1 1/2" shelf to rest on which is plenty. The 2 posts against the house sit on the sill timber. This design passed an engineering review as well.
This project was a weather tight sunroom so there was no issue of water getting into the house or behind the siding. This might not be the best solution if water can get to your sill beam.

[Roger Nair]

Carpenter, a couple of points,  you should rethink the subject of point loading.  Quote "A timber frame is only point loaded because all of the weight is carried by the posts."   A point load can be applied in a number of ways along the load path from ridge to foundation, with or without a post.  A beam for example can receive the load of multiple rafters and so that concentrated load when placed in a wall or another beam or a header is called a point load.  In the case of floor joists supported by a ledger that is called a uniform distributed load.  The methods for supporting uniform loads and point loads should not be mixed without some calculation mainly because not only are they different in kind but also in magnitude.

So I acknowledge that we are not dealing with a known design and force and this is no more than a gut reflection and the likely addition is small scale, nethertheless, treat a point load with a point load solution.

[witterbound]

Is this a timber frame porch, or a conventional one?