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Galatea 10-12-2010 09:48 PM

stairwell opening in wood joist floors
 
What do you do when the width of the opening of your new stairwell doesn't butt up against an existing joist! No opening has been cut yet...still in the planning stage of the game. We are converting our attic into a living space and need to install a stairwell. Our house is pretty old and the wood joists are 2"x10", 28" on center apart. The opening required is 5'-0" wide but this ends up between 2 joists. I'd have to put 5 trimmer joists to get to the next existing joist...there has got to be a better way to support the length of the opening!

jklingel 10-12-2010 10:16 PM

It sounds like you are walking up into the attic, parallel to the floor joists and will have to cut one floor joist off short and install a header. ???? I'm not sure I'm using the term "header" here correctly, but that is what I'd call it. You cut the joist, run a board or 2 perpendicular to it, and nail that to the joists on either side; the adjacent joists will now carry its load. (BTW: That may overload them, so have someone check out your plan. Any posts or supports for those adjacent floor joists going in to help them out?) Can't you just install a couple of blocking piece and run a board between it and your header, parallel to the floor joists? Maybe I'm not seeing what you are doing, but it sounds pretty simple; you are just hanging in a new, very short floor joist at the edge of the stairway opening. No? j

jlhaslip 10-12-2010 10:46 PM

1 Attachment(s)
The long joists are typically doubled with the "header" mounted using joist hangers.
The "header" is another double.
Also use a joist hanger to mount the cut joist to the backside of the "header".

BigJim 10-13-2010 12:04 AM

Quote:

Originally Posted by jlhaslip (Post 515978)
The long joists are typically doubled with the "header" mounted using joist hangers.
The "header" is another double.
Also use a joist hanger to mount the cut joist to the backside of the "header".

Jl is right on with the drawing. A question for you, how long is the span that your joist make? 28 inches on center might be too much for your joist if the span is too wide. If it were mine I would put another joist between the existing joist.

Galatea 10-13-2010 09:28 AM

drawing to go with my question
 
1 Attachment(s)
Attachment 25647

Here's a drawing of the existing joist and the location we're planning for our stairwell. Hope this help to better explain what we are dealing with.

BigJim 10-13-2010 11:26 AM

There must be a wall somewhere supporting the joist. The only joist I have seen that long are engineered and you said it is an older home so chances are they aren't engineered joist. I am not trying to be picky but we need to know exactly what you have before we can offer advise.

One more question, what is the pitch of your roof? If you have the stairs too close to the wall the rafters rest on you may not have enough head room.

Galatea 10-13-2010 01:03 PM

Additional Details
 
the walls beaneath (living room on main floor) are drawn in pink and . The roof pitch is 9:12. We are installing a pre-fabricated 48" spiral staircase. The celing height where the new stairs would exit onto the attic floor is 8'-0"

Galatea 10-13-2010 01:05 PM

drawing of joist plan
 
1 Attachment(s)
peak of roof is marked with a pink dashed line (left to right on drawing)

BigJim 10-13-2010 01:37 PM

Quote:

Originally Posted by Galatea (Post 516229)
the walls beaneath (living room on main floor) are drawn in pink and . The roof pitch is 9:12. We are installing a pre-fabricated 48" spiral staircase. The celing height where the new stairs would exit onto the attic floor is 8'-0"

As for head room you will be fine as you will have a minimum of 81 inches on the low side of your stairs. I would still be concerned with the spacing of your joists though. Another couple of things is you will be limited with the size of objects you will be able to get upstairs as the spiral stairs will be narrow. In this area we have to have another set of stairs as that is code. I really don't know how that is up your way but for sure a fire escape is a necessity. I would recommend talking to your code enforcement to be on the right side with them about the joist, extra stairs and fire escape.


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