From complex commercial buildings to simple garden sheds, the advent of the manufactured roof truss has simplified roof construction for carpenters and do-it-yourselfers alike. However, trusses are both flexible and awkward until they’re on the roof and braced, and it’s very easy to get injured during the installation process. You need to pay attention, take things slow and in the proper order, and observe some simple but very important safety procedures.
DELIVERY AND PLACEMENT
The trusses will be delivered to your jobsite via truck or trailer. Depending on the size and quantity, they will either be lying flat on their sides or be stacked upright on their bottom chords. The trusses will have been banded together at the factory, and securely chained or strapped down for transport.
Do not remove the transport straps or the metal banding — let the delivery driver do this. Releasing the wrong thing at the wrong time can cause the whole load to shift or tip over or can cause one of the straps or bands to snap back, either one of which can cause severe injury in an instant.
Typically, the delivery truck will come equipped with a crane for removing the trusses from the truck and setting them on top of the walls. Prior to delivery, you need to decide if you will have the crane place the whole bundle of trusses on the roof — something that is normally included in the delivery price — or if you will have them place the trusses in position one at a time for you. Individual placement is usually an additional charge, and is based on the number of hours that the truck and operator are on site. However, crane placement is the safest way to set the trusses, and is usually well worth the extra expense.
A good truss company will stack the trusses on the truck in the order in which they will be set on the walls — the first truss to go up will be on top of the stack, then the second, etc. The truss or crane company will provide the necessary straps for lifting the truss, but you should be prepared with a couple of ropes on-site for use in guiding the truss into final position.
Have the crane operator show you how and where to correctly place the straps on the truss, and then how to snap the lifting hook to the straps. A rope, called a "tag line," is tied to one end of the truss, and as the crane lifts the truss, a second person uses the rope to guide the truss into the proper position. A carpenter on each wall "catches" the truss as it arrives, and guides it to its exact location on top of the wall and then secures it in place.
If you are assisting with the placement of the trusses, be very careful around the crane! Always remain aware of where the lifting hook, cable and lifting straps are so that you are not struck by them. Also, make sure your work site is clean as you guide the trusses into position — as you maneuver the tag line, your eyes are on the truss instead of the ground, and it’s very easy to trip, step in a hole, or otherwise injure yourself.
Prior to placement of the first truss, you need to have bracing in place to stabilize it, and have additional bracing material on-site and ready to use. For a typical gable roof installation, 2x4s are attached vertically to the gable end wall so that they protrude well up above the wall plates. The uprights are also back-braced with additional angled lumber down to the ground. This provides plumb and secure support for the first truss to be braced against as installation begins.
Once the first truss is in position on the roof, it needs to be temporarily nailed in place against the upright 2x4s, as well as being permanently nailed in place to the wall plates. As each subsequent truss is swung up into place, additional bracing, typically 1×4 lumber, is extended out horizontally from truss to truss to secure each new one in place.
DO NOT remove the lifting strap from the truss until it is completely secured and braced. Remember that these trusses are very tall and wide in relation to the small surface area that is actually sitting on top of the wall, and if one tips over it will cause a domino effect that will topple anything that is not secured — with disastrous results!
SOME ADDITIONAL PRECAUTIONS
DO NOT ever walk on the trusses, even when braced — for all their strength, they are extremely flexible side to side until the roof sheathing is on. DO NOT ever lay a truss on its side across the walls — again, it is very flexible in that position and will not support ANY weight. Finally, DO NOT set anything on the trusses such as stacks of plywood, tools, etc., until they are completely braced.
Remember that these are just some very basic guidelines. Follow ALL manufacturer guidelines and building codes for safe handling, bracing, blocking and other installation procedures, and never attempt an installation that you’re not completely familiar and comfortable with.
Remodeling and repair questions? E-mail Paul at firstname.lastname@example.org.
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