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How to Build a Simple

Wood Truss Trusses are often used to build a structurally sound roof

system in a variety of buildings. Often, in simple projects like

small sheds, storage buildings, or other structures not

governed by specific engineering requirements or building

codes, it's possible to build your own trusses from ordinary

lumber. See Step 1 below to get started.

1 Determine if homemade trusses are suitable for the

project you're building.Since your truss will support

the roof of your building, it should not violate local building

codes and must be designed to meet wind load, snow load,

and other structural requirements.

2 Design your truss. You will need to know at least the basic

following design elements for your project.

3 Select the appropriate lumber for the truss you'll

construct. High density softwoods like southern

yellow pine or fir are preferred over lumbers like spruce, lodge

pole pine, and white pine. Other things to look at when

selecting individual boards include the following:

Size of the lumber. 2X4 inch (5cm x 10cm) nominal boards

are suitable for lightweight trusses if the bracing and member

connections are well designed and fabricated.

Quality of the lumber. Straight grained, dense boards with few

knots are preferred for this project. Try to select lumber with

no obvious splitting or barked edges.

Straightness of lumber. Twisted, warped, or crooked boards

do not lend themselves well for building trusses. Lumber with

a slight curve, or crown may be used, as long as the crown is

facing up when it is installed.

Lumber should be kiln dried or seasoned, as green lumber

may shrink and/or warp after the truss is assembled and

installed.

4 Set up sawhorses or another flat, stable work place to

build your trusses. If possible, draw out a full size truss on a

floor to help you establish the lengths of each member and

the angles of the various cuts required. If you cannot do this,

use sawhorses and set the bottom chord board on them to

begin the process of marking pattern pieces.

5 Place the bottom chord board with the crown up, then

place the boards the top chords will be cut from over it,

so each member laps where they will intersect when the

truss is built. Scribe lines for the cuts at these overlapping

places, cutting the bottom chord ends first if required.

6 Mark the top cuts on the top chords where they will meet

at the roof peak. The angle of this cut can be determined

with a speed square if you know the roof pitch. Mark

a common rafter pitch cut on each top chord, or use

a string to make a mark from the center point of the bottom

chord perpendicular to that member across the two top chords

where they overlap each other.

7 Determine whether the top chord or bottom chord will

overhang the eave of your building, and then choose the

appropriate bottom cut of the top chord. For a plumb eave

line, you should be able to use the same angle you

established to the top cut of the top chord. If you want the

fascia board (if you anticipate installing one) to slope inward,

use a sharper angle.

8 Locate the position of the intermediate diagonal bracing

members you'll need to complete the truss. There are

specific engineering guidelines and even online resources you

can use to determine load bearing and span applications for

your project, but this article only applies to simple trusses

where the general rule of thumb is one brace from the one

third points of the bottom chords to the center of the top

chords.

Divide the length of the bottom chord by three, then measure

the resulting distance across the chord, marking the two

locations where these braces will intersect the chord.

Mark the center point of each top chord, then place a board

long enough to overlap each chord so the angles of the

intersection can be scribed on each end.

9 Use one of each unique member you have marked and

cut as a pattern to mark subsequent members for each

truss you plan to build. Be careful to make sure top and

bottom chords are placed so their crowns are up when the

trusses are built, and take care to be as precise as possible

when marking and cutting each piece, as fitting them in the

truss will be difficult if the lengths or angles are not correct.

10 Determine if toe-nailing the members will create a strong

enough truss for you project. Likely, you will want to use

reinforcing plates, gang-nailers, or gussets for all the

connecting points of the frame members. The illustrations

included here show 16 gauge galvanized steel plates, cut

from salvages scrap metal being used, but if weathering isn't

a consideration, 1/2 inch (12.7mm) plywood plates can be

used.

11

Nail each member of the first truss together, supporting it

at intersections with additional boards or posts to keep

the assembly flat while it is laying on it's side. Use clamps

to hold the fitted pieces tightly together while fastening them,

and to work out any twists that are present in the lumber

you're using.

For metal or plywood reinforcing plates, use plenty of nails of

a length that will not penetrate through the member you're

fastening, or you will have to bend the protruding ends of

these nails over before putting the plates on the opposite side

of the truss.

12 Use the first truss you assembled as a template to

assemble the remaining trusses. Make sure all the joints

are supported by temporary legs if you're working on a

sawhorse or a table that is not large enough for the complete

truss to set upon.

13 Stack the completed trusses on dunnage so they lay as

flat as possible, and in the best alignment you can

achieve to prevent them from warping prior to

installation. Placing the trusses stacked in this manner will

also allow you to observe how well the trusses match each

other. Keep in mind that unless you have perfectly sized and

straight material, you can expect minor variations from one

truss to the next.

14

Install your trusses on the project you're building. Attach

them to the top plate securely, and in accordance with

applicable building codes.

Ez Wood Project Designer -

Just Use A Pencil

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