Framing For Attic Stairs

[crokett]

I put the attic stairs in today. I intended to add some 2x4s between the trusses that the stairs are hung from and the ones to either side to help carry the load. On one side I discovered a 2x6 that is the top plate for the wall underneath that the 2x4s would have to be notched over. So...

Double up on the 2x4s and notch them both?

Use a notched 2x6?

Or the option I like best, notch the 2x4, install it then install another flat over the top that spans the trusses.

[mdutch]

Is this a 2x6 pre-fab diamond truss system?

Um, maybe I'm not getting this, but why would you notch a 2x4? You'd compromise its relatively useless span strength. Especially on the flat. In general, I'd never notch any roof framing except the ends of the individual rafters at the outside sill plates.

To strengthen your opening, I would double up the trusses on the inside (or outside, depending on rough opening) with additional 2x6's (min. 8', max to reach interior wall sill bearings) to help stiffen them to carry the load. Then use a joist-hanger to add 2x6's across the span of the opening to complete your "box" for stair installation.

Or maybe I'm not visualizing the problem you have.

[crokett]

The trusses are 2x4 prefab. The stairs are already in. Stairs are hung between two trusses w/doubled 2x4s as headers. There is a wall below that runs perpendicular to the trusses and the stairs are hung about 1' off this wall. That was as close as I could get it for other clearance reasons. Additionally, the stairs are hung between where the webs meet the bottom chord. I figured it was strongest here. I added addtional doubled 2x4 blocking to one side of the stairs to carry the load to the next truss over. On the other side, there is a wall that runs parallel to the trusses. The top plate is a 2x6. It is between the truss the stairs are on and this next one over. To add blocking I would have to notch it over this top plate.

[JimD]

David,

I doubt that the stairs need additional blocking but I have a suggestion. I like to put a plywood box - could be solid wood - around the stairs and then put a door and weather stripping on the top of the box. It helps seal the stair opening minimizing heat/cooling impacts of the stairs. It probably also stiffens things up a bit. I make the upper door with foam insulation inside and door skin plywood on the outside. It hinges from the top side and I put a wire or string from the truss to use to hold the door open when I am going up and down. When I am done, I take the door off the wire and close it.

Jim

[crokett]

Hi Jim,

thanks for posting that. I had a vague memory of a similar post at some point but couldn't find it. I was thinking of buying a couple sheets of blue foam board and doubling them up to make a box that fits over the stairs in the attic. It cuts easily and is pretty light. To make it stiffer I thought I'd glue a 1/4" ply shell to the outside.