Tips on Installing Floor Trusses


Floor trusses are manufactured floor units that are constructed in a factory, shipped to the building site and installed by the contractor or homeowner. They are usually made from 2-by-4 lumber that is fastened together to form 24-inch-wide trusses that can span large expanses without being supported by posts. The trusses are specially built to the contractor or homeowner's specifications; however, they must be installed correctly once on site.

Installation Tips

  • Floor trusses must always be handled by more than one person. Always have a helper or two to help set the trusses. Before the trusses are set into place, make sure that sill plates are already in place. The sill plates are basically treated 2-by-8s that are attached to the top of a home’s concrete or block foundation. The plates are attached to the foundation using bolts that are fastened into the concrete. The plates serve as a means of fastening the floor trusses to the foundation using nails.

    Floor trusses should always be set on 16- or 12-inch centers, so marking your sill plates beforehand will give you a good idea of where to set the trusses. Laying out all of the trusses before you attach them will help speed up the job. It will also free up your helper after the trusses have been laid in place. You can go back and attach the trusses alone now. Pay attention when ordering your truss lengths. Leave 3 inches off the entire length to save space for the rim joist that will run around the outside of the entire trussed floor system--the trusses will be held together by the rim joist. The 3 inches represents the thickness of a 1 1/2-inch rim joist board on each side of the floor at the ends of the trusses. Beginning at one corner of the floor system and attaching the rim joist to the first floor truss will help keep the rim joist upright. Use 16-penny nails for attaching the solid rim joist to the floor trusses. The rim joist will align with the outer edge of the sill plate on the foundation. Angle nails through the bottom edge of the rim joist and into the sill plate to hold the rim joist in place. Make sure that the floor trusses are square and on center as you attach them to the rim joist.

Related Searches


  • \"Framing floors, walls, and ceilings?;\" Fine Homebuilding; 2005
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  • Photo Credit floor trusses image by jimcox40 from
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