1)	Ants are famous for their strength... but a roof truss can carry proportionately more weight than an ant.
2)	Over time, roof trusses can end up carrying increased loads from roof recoating jobs. We've seen older roofs struggling under three inches of tar!
3)	Trusses can and do break from another increased load: too much standing water on the roof. Water may not drain off fast enough because drains are blocked by debris, children's balls or other obstructions. It's not unusual to have 5,000 gallons of water on a roof. Each gallon weighs eight pounds... so the result can be 40,000 pounds (20 tons) of extra load on the trusses.
4)	You should tighten roof truss bolts every five years.
5)	Trusses in older buildings were designed for a 40 pound loading per square foot and usually require upgrading for today's new loads: sprinkler systems, an overhead crane, rooftop heating or air conditioning, a balcony or other additions.
6)	The load-carrying capacity of a truss system can be increased by adding tie rods, new trusses, top chord laminations, or by building truss tops larger.
7)	Nothing should be hung from the bottom of a truss (the horizontal portion)! This is not the load-bearing part of the truss. The top, where joists and sheathing rest, is the load-bearing member.
8)	You should never cut into a roof truss! Don't cut holes for pipes!
9)	The key indicator of a good truss repair job is if the top of the roof is level - it's probably a good job.
9)	Some things to look for in a bad truss repair job. Use of improper materials Failure to replace rotting sections Not jacking trusses up to the proper height, resulting in a flat spot on the roof. Cutting off webs that extend below the bottom chord. This makes the truss shallow or "flat." Flat trusses are weak trusses. Not using a transit to check truss camber before disassembly. Knots over 1" in top and/or bottom chords. Use of unsuitable laminated materials. Only laminated materials meeting American Institute of Timber Construction (AITC) standards should be used. Manufacturers licensed by the Institute must adhere to its standards. These standards require, for example, that kiln-dried lumber be used, and that individual laminates be bonded with waterproof adhesives. The Institute conducts unannounced plant inspections to ensure compliance. AITC certification is available to building owners, architects and other interested parties.