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Your points are sound, and reflected in the plates used on the trusses.
Some of the pressed in plates on both sides of the trusses are as small as about 3" by 4", so don't do much more than hold the trusses together during shipping, and limit lateral movement off the 2x its against. Thus the many plywood and OSB plates (I have a siding/coil nailer making generous use of nails easy).
I did far less on the shop side, where I installed an attic ladder and plywood flooring to allow storage of lightweight items (e.g., heaters, fans, tool boxes, holiday decor, empty boxes. . . .). Over ten years in and even with a 200 pound guy tramping around, all appears to remain well with just the adds of plates over the horizontals and swapping 2x's tying all the truss bases together for plywood (and hundreds of square drives).
On the hoist, the glue-lam ties to 7 trusses, with the hoist in the center. Even before being tied together, there was zero gap between the laminated flatstock and the truss bottoms. The lam got 3" screws to horizontal and vertical, to secure the position, then tensioned plumbers' tape wrapping it and the verticals it tied to.
There was a hugely notable difference in the behavior of the bottom truss 2x just from tying the lam. Adding sandwiched ply vertically was even more impressive.
Ideally, I'd sister 2x6's, or even secure 1/8" metal straps, screwed every 4", to the bottoms of the 2x's (think cable bridge - the metal doesn't stretch and bend like wood, so what would be about like adding two 2x6's or 8's, BUT would be fun to deal with when the rock went up.
Not visible, because they are temporary, used only when lifting, are ground to ceiling (under trusses) 2x's. I may grab a couple fabric/cyclone fence posts and set up a swivel mount for them on the ceiling. Labels on the pipes would help me remember what they do after a coffee break. ;)
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Regular Roof Trusses
Some of the pressed in plates on both sides of the trusses are as small as about 3" by 4", so don't do much more than hold the trusses together during shipping, and limit lateral movement off the 2x its against. Thus the many plywood and OSB plates (I have a siding/coil nailer making generous use of nails easy).
I did far less on the shop side, where I installed an attic ladder and plywood flooring to allow storage of lightweight items (e.g., heaters, fans, tool boxes, holiday decor, empty boxes. . . .). Over ten years in and even with a 200 pound guy tramping around, all appears to remain well with just the adds of plates over the horizontals and swapping 2x's tying all the truss bases together for plywood (and hundreds of square drives).
On the hoist, the glue-lam ties to 7 trusses, with the hoist in the center. Even before being tied together, there was zero gap between the laminated flatstock and the truss bottoms. The lam got 3" screws to horizontal and vertical, to secure the position, then tensioned plumbers' tape wrapping it and the verticals it tied to.
There was a hugely notable difference in the behavior of the bottom truss 2x just from tying the lam. Adding sandwiched ply vertically was even more impressive.
Ideally, I'd sister 2x6's, or even secure 1/8" metal straps, screwed every 4", to the bottoms of the 2x's (think cable bridge - the metal doesn't stretch and bend like wood, so what would be about like adding two 2x6's or 8's, BUT would be fun to deal with when the rock went up.
Not visible, because they are temporary, used only when lifting, are ground to ceiling (under trusses) 2x's. I may grab a couple fabric/cyclone fence posts and set up a swivel mount for them on the ceiling. Labels on the pipes would help me remember what they do after a coffee break. ;)
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Regular Roof Trusses
- Webbing: Feature a dense, continuous pattern of smaller triangular web members (often made of 2x4 lumber) throughout their entire structure. This configuration efficiently distributes the roof's weight and forces to the exterior walls.
- Open Space: Lack significant open space. The internal webbing obstructs any potential for a usable room or even easy movement and storage, which is why converting a standard-truss attic is difficult or impossible.
- Purpose: Designed solely to support the weight of the roof deck, roofing materials, and environmental loads (snow, wind).
- Appearance: The numerous internal members give them a very "busy" or complex appearance compared to the open center of attic trusses.
Attic Trusses (Room-in-Attic Trusses)
- Open Space: Possess a large, clear span area in the bottom center, which is the designated space for a room, storage, or mechanical equipment.
- Webbing: The triangular webbing is present, but it is confined to the sloped sections on either side of the open space (above the kneewalls).
- Structure/Size: They are engineered with larger, heavier timber sections for the top and bottom chords to support the extra dead and live loads of a floor (e.g., furniture, people) in the attic area, unlike standard trusses.
- Appearance: Visually distinctive due to the large, empty middle section, clearly defining where the floor of the attic room will be.
In short, a glance at the internal structure will immediately reveal the difference: standard trusses are filled with triangles, while attic trusses have a large, empty rectangle in the middle.
A standard 8-foot 2x4 can handle approximately 1,000 pounds (about 450 kg) of downward pressure when standing on end, with some sources citing even higher figures for stronger wood types. However, this is a general estimate, and the actual load capacity depends on the wood's species, grade, length, and how it's supported, with longer spans or weaker wood being less capable of holding a load.
A standard 8-foot 2x4 can handle approximately 1,000 pounds (about 450 kg) of downward pressure when standing on end, with some sources citing even higher figures for stronger wood types. However, this is a general estimate, and the actual load capacity depends on the wood's species, grade, length, and how it's supported, with longer spans or weaker wood being less capable of holding a load.
