Chapter 13: Roof Trusses

Installing the roof trusses is an exciting project. Both roof trusses and sheathing (described in the next chapter) can be installed in one day by an experienced crew. Most of the work is off of the ground. Only workers who are comfortable with heights should install trusses. Volunteers with medical conditions or who take medication which causes dizziness should not install roof trusses. Other projects can be found on the ground.

If building a one story house, the gable ends may be assembled on the ground. A crane may or may not be used to get the trusses onto the roof.

2. Safety Issues

• Review the Morning Safety Huddle Talking Papers for Roof Work with the Volunteers.
• No walking on the cap plate of the exterior or interior framing.
• All workers who are working off the ground should be comfortable working at heights and not have any medical condition making this unsafe.
• No one should be working beneath crews working above the ground because of the risk of falling materials. If someone must be below, they should wear a hard hat.
• Ladders should have firm footing and be at a safe angle. A coworker should support the ladder at the bottom whenever a worker is mounting or dismounting a ladder.
• Workers should be certain that they only step on secure structures.
• Power tools should only be used by people trained in their safe use.
• Eye and ear protection should be used when using power tools.

3. Prior Tasks to Have Been Completed before Beginning

• Exterior walls have been straightened
• Cap plate on all framing
• Beams on porch are temporarily braced before stepping on them (if applicable)
• Materials ordered and on site

• A crew of 3 - 4 gable ends (if applicable)
• 2 crew of 5 to raise trusses
• 2 crews of 4 to prepare and install fascia board
• A crew of 3 to be the saw crew, one cuts the others stabilize and transport materials.

____Build ladders on interior walls to support walk boards
____Layout truss locations on cap plate
____Build gable ends (if applicable)
____Trusses lifted to top of house
____Trusses raised, secured, and braced
____2 x 4's nailed to side walls to act as trusses (on two story house)
____Trim tails of trusses if needed
____Trim and install fascia board
____Build returns (if applicable)
____Frame attic access (if applicable)

6. Tools/Equipment List

• Extension ladders
• Step ladders
• Walk board
• Hammers
• Circular saw
• Table Saw (optional but useful)
• Tape measures
• Pencils
• Speed square
• Carpenter's square
• String
• Extension cords
• Saw horses (2)
• Hand saw

7. Material List

• Trusses
• 2 x 4's (longest lengths available)
• Nails 16d, 8d
• ½" sheathing
• Truss braces
• Truss clips
• Hurricane braces

____Gable end is assembled and sheathed (if applicable), vent hole cut out
____Proper layout for trusses on cap plate
____Trusses raised, secured, and braced properly
____2 x 4's nailed to side walls to act as trusses (on 2 story)
____Fascia board installed correctly
____Hurricane braces installed correctly so they will not interfere with drywall
____Attic access framed properly (if applicable)
____Returns built properly (if applicable)

9. Construction Drawings and Text

NOTE: The following drawings, diagrams, and text are to be used on the job site when a question arises as to methods and procedures associated with the task. The notes on the drawings have been geared toward use as a quick reference. If a more in-depth explanation is needed, please read the text description. But most importantly, consult your Habitat Site Supervisor and Construction Manager for advice as needed.

Cap plate layout
The cap plates should be marked with the locations of the trusses. This will be done similarly to laying out the exterior walls, except that the trusses will be marked with 24" on center rather than 16" on center. Layout should be done from the end of the house specified in the plans. The cap plates of the hall walls should also be marked.

Assembling gable ends (if applicable)
The gable ends are assembled on the ground and will be lifted into place later by a crane. The gable truss should be laid on a level flat surface. 2 x 4 material is nailed to the back of the bottom of the truss so that it is flush with the bottom. It should be nailed so that the 3 ½" surface extends back from the bottom of the truss. This surface will lay on the top of the cap plate and will be used for a nailing surface. It will also overhang the cap plate and be used to screw the ceiling drywall.

A string should be used to ensure that the bottom chord of the truss which will sit on the cap plate is straight and stays straight. The gable truss is sheathed with ½" sheathing nailed every 8" with 8d nails, 6" on the perimeter. If the gable end is to receive blue board, it is a good idea to install the blue board now rather than after the gable end has been installed. The seams in the blue board should not coincide with the seams in the sheathing. The front gable truss should not be sheathed where the porch trusses will tie to allow for circulation. The porch gable end is done in the same manner.

Assemble a ladder assembly with one 2 x 6 and one 2 x 4 connected by short 2 x 4's every 2 feet. It should be the width of the overhang. The assembly is nailed to the front of the gable truss. The 2 x 6 will be the fascia board. Nail this ladder assembly to the front of the gable truss.

A hole may need to be cut in the sheathing at the peak for the crane. Check with the HFHSTL construction staff.

Installing the Gable End (if applicable)
The gable end will be lifted to the top of the house with a crane. Once lifted, volunteers will need to position the gable end so that the front of the blue board on the gable end aligns with the blue board of the exterior wall. If blue board will not be installed, then the sheathing is aligned. The gable end is then centered, measuring the overhang of the tail on either side of the house. It is nailed in place every 12 inches with 16d nails.

Raising trusses
It is very useful to use walk boards when installing the trusses. The walk boards will be run perpendicular to the direction of the trusses. There should be one on either side of the house and one down the center. Use 2 x 4 bracing nailed into the wall framing to build bracing on which to place the walk boards. As the bracing will support the walk boards and the people on them, use as many braces as possible and make sure all are securely nailed.

The trusses will be stacked on the top of the house using the crane. They can be lifted manually, but this is uncommon. Prior to raising any of the trusses, the gable end needs to be installed on the one story houses. The crane will lift it into place. The tails should have equal overhang on both ends. Nail through the 2 x 4 that was nailed to the bottom chord of the gable truss into the cap plate every 12" with 16d nails. The second truss will need to be secured as described below.

On the one story house, there are several methods to align the trusses the entire length of the house. One method is to pull a string from the tails of both gable trusses and align the tail of each truss with that line. Another method is to place each truss at the location of the marks and center the truss so that it has equal overhang on either side. Each truss should be raised individually by a crew of 3 people. On each side wall it is secured by toe nailing 3 16 d nails. If the truss crosses interior walls, a clip is installed which will attach to both the truss and the cap plate. These slotted anchor clips will allow the truss to float or move up and down with changing atmospheric conditions. This will reduce drywall cracks in the corners between the walls and the ceilings. If unfamiliar with these clips, ask HFHSTL staff for instruction. Between each pair of adjacent trusses, bracing is installed. 22 ½" brackets are attached using a hammer. Make sure that the trusses are pulled completely together prior to securing. Attach 2 brackets between each set of trusses on each side, at one third intervals. If these brackets are not available, use 1 x 3 or 2 x 4 material marked 24" on center and nailed with 1 8d or 16d nail (leave the head up for easy removal) into the top of each truss. These boards would need to be removed as the sheathing is applied.

On two story houses, the trusses are stood in place and nailed with 3 16d nails. At one end the truss will likely be attached to a wall. Blocking may need to be installed so that the truss can be nailed into the wall, again with three nails. Trusses will probably not be used next to the walls. If this is the case, 2 x 4's will be nailed to the wall framing. Determine the location by determining the front and back elevation from another truss. Snap a chalk line using these dimensions. Nail the 2 x 4 with two 16d nails into each wall stud.

Bracing the trusses All bracing will come with a bracing pattern determined by the manufacture. As the trusses are installed, temporary bracing is used and then permanent bracing is added according to the plan.

On the one story house, the gable truss should be temporarily braced once installed. A 16' 2 x 4 is cut with a 45 degree angle at one end and nailed near the top into the side of one of the supports near the middle of the gable truss. It is then anchored to a solid support, most likely the hall wall. The bottoms of the next few trusses should be moved toward the gable truss and the 2 x 4 should be fed through these trusses so that the trusses may be raised without removing the bracing. After the trusses are all raised, a 2 x 4 can be nailed across the tops of the bottoms of the trusses and the long 2 x 4 can be cut and anchored to this. An alternate method of temporarily bracing the gable end is to brace it to the outside of the house. Two 16 foot 2 x 4's are overlapped and nailed together. One end is nailed to a stake and the other to the gable truss. Permanent bracing is put inside the house after the trusses are all up.

As each truss is raised it should be braced. Use metal braces to align and secure each truss to the previous truss. The braces should be placed at thirds on the trusses. Make sure to pull the trusses tight to both ends of the brace prior to hammering it into the trusses. If this is not done, the mistake will be translated throughout the trusses and may produce additional problems. If the metal braces are not available, mark a 1 x 3 or 2 x 4 for the trusses at 24 inches on center and nail to the top of the trusses.

Attic access
If applicable, an attic access should be framed at the end of the hall. 2 2 x 4's should be cut to 22 ½". These should be nailed between 2 adjacent trusses forming a square.

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