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Sample Square Dome Garage Design

To illustrate how easy it is to build a Square Dome design here is a sample garage you can build.  The design is a single layer half dome supported by stud walls.  If you build an interesting version of this design, send us a digital picture so we can include your dome on the web site.  There is no charge for using this design.  Follow the instructions carefully to create a safe structure.  The design is provided as-is and it is the responsibility of the builder to determine the suitability of the design for any intended use.

Fabricating Square Dome Wooden Structures

In wooden Square Domes elements form the sides of panels.

In Table 1 headings A, B and C refer to vertices; AREA refers to the cross sectional area of the element having vertices A and B; EE-LEN refers to the end-to-end length of the element; HGHT refers to the element height; EDGE< refers to the edge angle of the element; C is the third vertex in the panel; ATIP is the angle at the A tip of the element; ATILT is the angle of the saw blade to make the cut at tip A; likewise BTIP and BTILT are used to cut the end of the element having vertex B.  <ACB is the angle formed by the vertices A, C and B and is included for reference only.

Note that the cross sectional area listed in Table 1 is the combination of the areas of both elements in adjoining panels.  For example, if the table lists an element having an AREA of 10.5 square inches, that means the panel sides that form the element are each 5.25 square inches (2 x 4 lumber having actual dimensions of 1.5 x 3.5 inches)

1.) Element lengths are marked and cut and vertex numbers are marked per Table 1.  Underlining the vertex numbers will avoid the possible confusion of reading them upside down.  Once elements are cut, care should be taken that cut areas remain clean until glued.

2.) Bolt holes are drilled on a drill press using a simple jig.  Holes can be drilled with a hand drill, but this is more work and less accurate than with a drill press. Holes are to be located at half the panel height from the top of the element.  The panel height is given at the bottom of Table 1.   Holes should be located at 3/4 panel height from the element ends. The size of holes should be just large enough to accept bolts with a diameter approximately 10% of the panel height. See Fig.1.


3.) Edge angles are cut per Table 1 and Fig.1 giving elements a proper edge dimension.


4.) End angles are cut per Table 1 and Fig. 2.  Set angle ATIP with a miter and ATILT (tilt angle of blade) and make the cut at tip A.  Do the same for tip B using BTIP and BTILT.


5.) Elements are joined to form the triangular panel frames (Fig. 3) using appropriate high strength glue and nailed or screwed to stabilize the joint while the glue is setting.  Most of the strength of the panel and the resulting structure is derived from the strength of these glued joints, so high quality waterproof glue is essential.  Resorcinol and some phenolic resins provide high strength bonds.  A good glue will be stronger than the wood itself, ensuring that the maximum strength of the wood is utilized.

6.) The triangular panel frames can then be used to trace the panel dimensions on the inner and outer panel plywood.  Panel plywood is cut and the outer panel side is glued and fastened (using nails or screws) to the panel frame.  Insulation, such as fiberglass with a vapor barrier, should be taped to form a long, wide strip that can be cut with a utility knife using the panel frames as templates and then stapled to the inside of the panel frame.  After tracing and cutting the inner panel material and marking it for later assembly the panel itself is ready for final assembly.

Square Dome Designs with 3-D trusses are provided with additional instructions and drawings and diagrams for creating the tripods that increase the dome strength for large structures.

Final Assembly of SDI Domes

Panels should be assembled beginning in a corner of the building, proceeding toward the diagonally opposite corner.  Glue is applied to the panel sides (shown in black in Fig. 3, side view, with a full coating of glue near the bolt holes and corners) and the panels are sequentially joined and bolted together.  Again, high quality glue is essential to develop the full strength of the structure.  A glue should be used that won't be effected by moisture and has a long life strength at least as great as the wood itself.  Bolts and nuts should have large flat washers to prevent the wood panel sides from being crushed when the bolts are tightened during assembly.

The cross section of the outer perimeter of the dome will be composed of the panel side elements and an additional perimeter element to make the perimeter section area equal to the other elements in the structure.  This additional perimeter member can take the form of a "cage" resting on the structure's vertical supports at the beginning of the assembly of the structure.

The outer edges of each dome have a uniform angle from vertical (given at the end of Table 1) to mate with column or masonry walls finished with the same angle.

Care should be taken that no adverse weather conditions such as rain, high winds or snow loading will occur during construction.  After the panels are assembled the inner panel material can be fastened to the inside of the dome and your dome is complete.

If technical assistance is required contact the SDI Design Department.