Cutting ceiling joist for attic ladder install

Question

Looking to take advantage of some open space in our attic and want to install an attic ladder. This would require cutting some of the ceiling joist. Before I do can anyone help me answer the following questions:

1) Can the joist be cut to make room for the attic ladder.

2) How much weight could the ceiling joist hold

Some details:

• Single story house built in the 1940s

• Ceiling joist are 2x4

• Ceiling joist are support by a wall that runs roughly down the middle of the house

Hopefully the attached pictures provide additional info.

Answer 1

I would not put the attic stairs/ladder assembly opening at right angles to the ceiling joists. You potentially compromise too many of the rafter cross ties by doing that. Instead you should place the cutout opening inline with the ceiling joists/rafter ties. This way you only need to cut one of them to make the room for the rough framing opening.

As evidenced from your pictures of the attic area, your roof support structure is not created from engineered trusses. Instead you have open rafters that depend almost completely on the rafter cross ties to triangulate the rafter structure and keep the building side walls from spreading out at the top due to roof loading. This is the reason why you want to minimize the number of these cross ties that you end up cutting into.

This also means that you may need to be a bit more flexible as to where you locate the rough opening relative to what is built below the attic ceiling. It is often considered optimal to place the attic stair access in a hallway. The consideration of the rafter tie direction and subsequent placement of the attic stair location may very well place some constraints on where the stair opening can be located. That may end up placing it in the ceiling of a bedroom for example.

Another thing to consider is to make sure that you are able to orient the attic stair so that it comes up at its top in a location that has plenty of head clearance under the rafters. This may very well mean that the top of the attic stair needs to face toward the center of the building structure where there is the greater overhead clearance to the rafters.

Answer 2

Yes, you can typically cut through joists, but you must make some additions known as trimmers and headers to the framing as well. Like this...

Note that the trimmers run the whole length of the joists in place.

The ceiling joists will not hold much weight being only 2x4’s. I would not expect to be able to install plywood and flooring and walk around up there, but you could possibly store some lightweight things at the edges of the space and over the wall below.

Answer 3

Similar to @paul's answer to your first question, but some additional information taken from this:

• If header spans a space less than 4ft, a single header can be used (as opposed to double), and it can be end nailed to the trimmer joists.
• If header spans 4ft or more, headers and trimmers must be doubled.
• Doubled trimmer joists must be nailed together with two 16-penny nails every 16 inches
• Doubled headers spanning up to 6ft can be end-nailed. Beyond 6ft, use hangers.
• Tail/cripple joists over 12ft should have hangers.
• If double trimmers must be used, they need only extend from the outside edge of the nearest load-bearing wall to the outside edge of the other nearest (in the opposite direction) load-bearing wall.

...

Update - I found applicable code here: https://codes.iccsafe.org/content/IRC2018P3/chapter-8-roof-ceiling-construction#IRC2018P3_Pt03_Ch08_SecR801

Use your browser's search function to find "R802.9 Framing of openings"