Table of Contents
This bridge was constructed entirely on the back lawn, showing that you do not always need an elaborate workshop or shed to undertake such a project.
Lumber sizes
The measurements throughout this project are given in both Metric (mm) and Standard/Imperial inches.
The metric measurements (mm) are given first followed by the imperial measurements (inch) in brackets ().
There are only two stock sizes required for this project, both being common stock sizes.
They are…
90mm x 45mm (1 1/2″ x 3 1/2″) and 90mm x 19mm (3/4″ x 3 1/2″).
90mm x 45mm means wood that is 90 millimeters wide by 45 millimeters thick.
That is called the actual size. The nominal size of the wood relates to its size prior to being dressed (planed, surfaced, smoothed). For example, wood that is 100mm x 50mm (nominal size), becomes 90mm x 45mm (actual size) once it has been dressed (planed, surfaced, smoothed).
And the equivalent in standard…
1 1/2″ x 3 1/2″ means wood that is 1 1/2 (one and a half) inches thick by 3 1/2 (three and a half) inches wide.
That is called the actual size. The nominal size of the wood relates to its size prior to being dressed (planed, surfaced, smoothed). For example, wood that is 2″ x 4″ (nominal size), becomes 1 1/2″ x 3 1/2″ (actual size) once it has been dressed (planed, surfaced, smoothed).
Note: The 90mm x 19mm (3/4″ x 3 1/2″) boards used for making the arches must be premium and knot free. If there are any deformities in the boards, then they may snap when bending pressure is applied.
Many thanks for the article on the laminated bridge. My daughter had asked me to build her a bridge to go over her pond, and after looking at many plans I decided that I could cope with your plan. I had been given a lot of mahogany by a friend who lives near by from a conservatory they had pulled down…
Harry from England
I need a arched bridge that would span a creek that is 12 feet wide with sloped banks
How do you cut the arch in two with a circular saw? (4) 1×4 beams laminated together will be 3 inches thick, but most circular saws can only cut to a depth of 2.5 inches. Also, that’s a long cut – how do you keep it straight?