Truss roof frame attic storage
29 July 2006
A. You are responding to a natural instinct that drives us to fill any accessible empty space within our dwellings with stuff. It's a cousin of that "nature hates a vacuum" rule. It's a powerful urge. Those of us who succumb to it completely are called pack-rats both to our faces and behind our backs. We all seem to succumb to this urge to some degree. A trip through someone's attic, basement or garage tells all.
If you are a new townhome owner then you might be a first-time home-buyer. You are in a perfect position to get a rational grip on these storage cravings early on.
I know it's hard to look at that access panel in the ceiling of your upstairs hall or closet and not give in to the urge of getting up there and packing things away-- but try. The hatch is there as a code requirement to provide access for people like p lumbers, electricians, inspectors, exterminators or fire-fighters to do their jobs when they have to. They don't need an obstacle course of every useless item you own that will fit through the opening.
The type of attic and roof framing that you have is called a truss system. The rafters and ceiling joists are comprised of a series of pre-engineered wood assemblies called trusses that-- from the end-- look like a wide triangle with a big wooden "W" in the center, attached to the tops and bottoms with metal plates called gussets. All of the pieces of these trusses are normally no bigger than two by fours.
During construction they are stood upright over the top floor, perpendicular to the front and back walls of the building, at two foot intervals and the roof sheathing plywood is laid and nailed over the tops forming the sloping roof surface. To the untr ained eye this whole assembly looks pretty flimsy, but let me assure you, when assembled and nailed correctly, they are surprisingly strong.
Whoever told you that they are not designed to have plywood put on the bottom chords (ceiling joists) is more right than wrong. The whole assembly is designed to handle stresses placed from above-- the roof side. No concern was given to the bottom chor ds other than being able to have the ceiling drywall of the room below attached to it and the ceiling insulation, usually blown fiberglass or cellulose, installed over the drywall and between the members.
As for installing a pull down staircase let me give you a word of warning. Install it between the trusses parallel to the bottom chords. They are designed to fit that way. That will generally force you to place the drop staircase in a bedroom to get it i n a position where you can you pull the stairs down, folding them out and still be able to climb up them. At no time should any of the top, bottom or cross truss members be cut for any reason, such as to install a drop stair or to open up space for air-c onditioning equipment or storage considerations. In fact, if a truss is damaged, cut or broken during construction, the repairs have to be designed by a truss engineer before the local building inspector will accept it. The temptation of installing them in the hallway will surely involve cutting at least two of the bottom chords of the trusses in your way as you are now installing the stairs perpendicular to the way the trusses are set. I unfortunately see them cut all the time and get perplexed look s when I tell folks what has been done.
Now, I might get in trouble with my engineer friends, but in the last 30 years of my life around trusses I have never seen a failure due to homeowners storing things in the truss space. I've seen damaged ceiling drywall from an accidental foot slip and nail pops from the activity of attaching flooring above with hammers and nails but as long as the trusses remain intact there seems not to be a problem.
If plywood is placed directly on top of the two by four ceiling truss chord you will compress the insulation down to the three and a half inch dimension of the two by four and reduce its insulating R-factor. You don't want to do that.
I've seen people attach wood ledger boards to the truss webs above the insulation and put the plywood for storage over that. That's a good plan. Don't nail anything up there, use screws. Inch and a quarter drywall screws are best. The shock of nailing will play havoc with drywall below, causing nail pops and seam splits.
After you've built what you must to gain storage in the truss space, don't store anything much heavier than empty suitcases or Christmas ornaments up there. Keep all the college text books and bowling balls down in the basement.