7 posts / 0 new
Last post
tubbfan
attic ladder
tubbfan

I wish to install an attic ladder above my garage. There already is an access measuring 30" x 31". In addition, the attic has plywood installed over virtually the whole area.

I've looked at attic ladders on home improvement warehouse sites and they generally come in two configurations: 22.5 inches wide and 25 inches wide. The rafters (or trusses) are 16 inches on center from each other.

How do I determine which attic ladder width to purchase and how do I determine which way to orient the installation?

Thanks in advance.

dj1
Re: attic ladder
dj1

To create space for a folding attic ladder, you will need to re-frame an opening, so you need to have at least intermediate framing knowledge and experience.

You can find instructions in books or on line (hopefully with diagrams or pictures), but basically, you will have to cut the length desired out of one joist, then double the adjacent joists to the right and to the left of it and finish with double blocking on both ends of the cut.

A. Spruce
Re: attic ladder
A. Spruce

Word of caution, you never want to cut any truss, particularly a manufactured truss, without knowing what you are doing or consulting an engineer. Cut it in the wrong spot or reinforce your cuts improperly and you are destined for serious problems down the road.

dj1
Re: attic ladder
dj1

Spruce, thanks for the alert, my answer was specifically for joist framing.

A. Spruce
Re: attic ladder
A. Spruce

Don't worry, I got your back! :cool:

dj1
Re: attic ladder
dj1
A. Spruce wrote:

Don't worry, I got your back! :cool:

I noticed...here's a bud for you !

Fencepost
Re: attic ladder
Fencepost
A. Spruce wrote:

Word of caution, you never want to cut any truss, particularly a manufactured truss, without knowing what you are doing or consulting an engineer. Cut it in the wrong spot or reinforce your cuts improperly and you are destined for serious problems down the road.

^^^This.

Truss systems are engineered not just for vertical load, but also for lateral load from wind. You might figure that you can cut and reinforce a truss a certain way and it will still be good for static, vertical snow load and the load of stuff in the attic, but if you don't account for the lateral wind load you can have problems. Once you consider lateral loading, you realize that the engineering just got a lot more complicated: for example, the angled portion doesn't just have downward forces: when the wind is against one side, that side experiences a downward force, but that force may be transferred to the opposite angled portion which then experiences an upward force.

Joists and rafters are kind of an over-engineered solution with a lot of resilience. Trusses are usually engineered for very specific loads. If you have trusses and they were not designed with attic storage in mind, then you must assume they are not sufficient for attic storage unless an engineer tells you otherwise. Converting an truss attic into a storage area can easily overload the trusses in ways they are not designed for. Also, the trusses do not work individually; they work together. There is often cross bracing (1x stock) nailed across the trusses; the truss engineer specifies where and how this bracing is to be installed. This transfers load from each truss to the adjacent trusses. Cutting or removing this bracing can compromise the strength of the roof system.

Now there is a possibility that there is enough safety factor in your roof system that you could modify things. But I'd recommend consulting an engineer, to be on the safe side. If there was a problem traceable to something you did, your insurance company might not be so accommodating.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.