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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.

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    Can you orient the unit in line with the joists rather than cutting through multiple joists? – Kris Sep 2 '18 at 0:17
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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...

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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.

  • Notice that OP has attic stairs crossing joist layout not with them. In addition the 2x4s are not particularly strong even before cutting through 4 if them – Kris Sep 2 '18 at 0:58
  • It doesn’t matter if the long side of an opening in a joist platform goes along or against the direction of the joists. The same principles of framing apply either way. The headers carry the load that the cut joists are carrying to the trimmer joists. – paul Sep 2 '18 at 1:02
  • Thanks for this info! I can install the attic ladder in the direction of the joists. However, now I'm wondering if the effort is worth it knowing that I'll not be able to put that much weight on those 2x4s. – slock Sep 2 '18 at 15:57
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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.

  • Thanks Michael! I'm wondering if the effort to install the attic ladder is worth it now that I know that I can't put much weight on the 2x4s. If I end up deciding to, and install it in the direction of the joists, would I just need to add the double headers and another 2x4 between them placed at the width of the attic ladder? – slock Sep 2 '18 at 16:08

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