How to Install Roof Trusses

How to Install Roof Trusses

on 09/16/2006

Installing roof trusses can be a tricky business. One person with lots of experience, building know-how, strength, dexterity and a dose of good luck might could pull off the job, but otherwise, plan on having at least one other helper, preferably more.

As you learn how to install roof trusses, one of the first things youll realize is that it is important to get the roof closed and protected against rain and other types of damaging weather as soon as possible. However, you also dont want to get in such a hurry as to make mistakes that could result in terrible consequences (such as roof truss failure ) on down the road from not properly mounting, positioning, and fastening the truss to the house.

Handling and Marking Anchor Points

Another critical part of how to install roof trusses is learning from the very beginning about their strengths, and their weaknesses. The strength in a truss lies in its vertical pressure resistance, not in any horizontal pressure. This means you dont want to lay the truss on its side against a wall or handle it any other way except from the top or bottom.

For homes higher than one story, you will almost certainly need a crane or levered ropes to get the truss to the top and in the correct position to avoid damaging it.

Mark anchor points every two feet (61 centimeters) to serve as guides as to where to affix the truss to the outside house walls. This important part of how to install roof trusses can save lots of work and help prevent you from having to measure once youre up in the air, where too much movement could be dangerous.

Measurements taken from the ground are also more likely to be accurate those taken up on top of a roof. Start installation at the end of the roof where the gable will be and continue from there.

Nailing Bracing and Installing Plywood for Fascia and Roof

Most pre-fab roof trusses come with one-by-fours used to separate them and hold the bracing of the truss in place. After youve finished anchoring the truss to the outside walls of the house, as part of knowing hot to install roof trusses, you need to know that these should be nailed permanently into place. The manufacturer providing the trusses should have these instructions included with the truss as part of the installation.

Although trusses provide the structure for eaves, you will still need to install the fascia. How to install roof trusses includes knowing this to help close off the roof and prevent rain, hail, or high winds from damaging the roof and house. Plywood roof panels should be installed at right angles to the trusses with joints offset.

Nail plywood-roofing panels every two feet (61 centimeters) between the trusses and use H-clips to attach the panels one to another. And with that youve learned some basic knowledge about how to install roof trusses. Remember though, that installing roof trusses, a fundamental part of building your house, needs to be done correctly, so even if it doesnt seem to make sense, take your time to do it right.

Tips for Installation

1) Since trusses come in various sizes and shapes, you should choose the kind that works best for your project. If your roof has an offset area, you will have to install two perpendicular sets of trusses next to each other. When those are set up, the inner trusses will be a ledge for the rest of the trusses to sit on and be installed.

2) As you start, the goal is to place a truss every two feet on center. Before you can do this however, you need to prepare the roof’s top plate. Place two-inch block spaces along the top so that the inner wall and the top plate are flush, which will then allow for the truss ends and the outer wall to sit flush. The trusses will also be able to be secured to the spacers, which can function as nailer blocks.

3) Reference marks should be made every two feet on center, placed around the edge of the top plate. This shows where each truss’s edge will align – use a clear marking scheme such as an ‘x’, because then each truss can sit directly over an ‘x’ without confusion as to which end of the mark the truss should be placed.

Positioning the Trusses

4) If you’re working with an irregular shape, lift the first alcove truss into place upside-down, using a long brace to turn it over and place it into the right position. When this has been secured to the top plate, it will be in place temporarily – later on, it will need to be secured down permanently. This should be continued for all the rest of the trusses along the alcove.

5) The first main truss can be secured to the back wall of the building, getting it in place on the vertical bracing. When carrying the trusses into the building, they should be held upside-down and then lifted up with a long brace. From here they can be turned up the right way and placed easily on top of each wall.

6) Once each truss is positioned in its place, it should be fastened to the top plate using toe-nailing to hold it together securely. After several trusses have been lifted and placed, they should be temporarily secured together using a horizontal brace. This will ensure that they don’t move, and continue to keep their correct alignment.

After the Trusses Are Placed

7) Following the same steps for the rest of the trusses, the roof construction can then be completed when they’re all in place. Plywood sheathing can be attached to all the gable ends – this should be the same kind of sheathing that was used on the walls earlier in the project.

8) Ladder-design structures can then be rigged up to get the necessary roof overhang over each gable. One should be made for each gable section and then fastened into place.

9) Some of the ends of the trusses will still be exposed at this stage, and 2’ x 4’ boards should be secured to their ends to create a sub-fascia. Then the rest of the roof can be covered in plywood sheathing. starting at one corner and using a chalk line to mark on the wood where the roof trusses are located. This will help to show where the sheathing will need to be secured to the trusses after they’ve been covered.

Roof 4: How to Install Roof Trusses

You are going to build a house or add an addition to a house. The house plans are drawn up, the house foundation is about to be started. It’s time to order the roof trusses. Most roof truss factories take at least two or three weeks before they even start to make up your roof trusses, depending on their back log. Don’t leave it until the walls are framed and then decide to order the roof trusses. You want that roof on and the roofing applied before rain or the elements do harm to the sub-floor and framing.

The house plans usually give the outside measurements of the walls on the Floor Plan. Some framers have these measurements coordinate with the outside of the sheathing, others prefer to go with the outside of the framing, that is the outside of the 2×4 or 2×6 walls. Personally, I go with the outside of the framing.

Determine how the house will be laid out and order the roof trusses accordingly. The main thing is that when the roof trusses are pre-ordered, make sure the framing is accurate and according to the measurements that will coincide with the size of the roof trusses when they come on site.

With delivery of the roof trusses, you should receive a package from the roof truss plant specifying the bracing required for the roof trusses as well as their safe handling and other pertinent information for each roof truss or set of roof trusses. For example, large roof trusses require 1×4 continuous bridging every 10 feet across their span including at the center of the webs. If the webs don’t line up with each other, notice the explanation of using "L" or "T" braces nailed to each individual web. Hip girders that are doubled up will show the number and spacing of nails. Hip trusses will show 2×4 strapping required on top of them. Valley sets resting on open roof trusses will be shown. Usually each individual roof truss has a number marked on it and a matching drawing to show their engineering specs and bracing requirements.

Initially, you and a partner will either unload the roof trusses off the truck using the truck crane to place them across the top of the exterior and interior walls of the house, or set them on dunnage on the ground. The walls at this point have been properly secured, braced and laid out for the truss centers. If on top of the walls or laying on dunnage on the ground, place the roof trusses upside down at the opposite end of the building you intend to start erecting them from, if there are no interior walls. If there are interior walls, pile them up on the end of the building across the tops of the walls. Slide or carry the first roof truss, still upside down, to its position that is marked on the top of the double plate. It is handy to get a third person to help swing the roof truss into the upright position. Set the end of the bottom chord flush with the outside wall. When ordering the roof trusses you specified the particular span, whether the span included the framing or the sheathing. This point is where the roof truss bottom chord flushes up. The roof truss is toenailed into position using 3 — 3 1/4" common bright nails through the bottom chord into the double plate. See: Tables 6: Nail Table One nail on one side and two nails on the opposite side on each end. Space the nails out and not too close to the end of the chord.

The first roof truss is braced temporarily, usually to a convenient inside wall, or with the use of supports nailed to the gable end wall and attached to the roof truss top and bottom chords, as shown in the drawing.

The second roof truss is then carried over to its designated position as marked on the plate and swung upright and toenailed securely to the double wall plate. A temporary 1×4 is nailed to each roof truss near the ridge to prevent them from falling over. Set the roof truss to the correct spacing when nailing to the 1×4. Continue this procedure. Before coming too close to the end of the building it is best to stand the remaining 2 or 3 roof trusses up, while you still have the room to swing them into their upright position, if hanging upside down. Just lean them against the upright, nailed in roof trusses and start from the opposite end sliding them into position carefully. Use another length of 1×4 to secure the end roof truss to the others at the ridge, tying the entire roof together.

Hurricane clips are installed after all the roof trusses are in place, by nailing them to the face of the double plate and into the sides of the roof truss bottom chord. The continuous bridging of 1×4 is nailed to the bottom chords and webs if specified. Brace the roof trusses accurately before the sheathing is applied. After the sheathing is nailed remove any temporary bracing of the walls and roof trusses.

In most jurisdictions the inspector will require an engineer to inspect the roof trusses for correct assembly. Your roof truss plant should have a name or two of engineers that will come to your site and do this inspection. Have the spec sheets ready to present to him. He will use these to verify that they are installed correctly, with adequate bracing and nailing.


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