Reality Check: Nails - Theory vs. Reality (advice for Structural Engineers)
Updated: May 30, 2022
If the tables in our design codes are to be believed, there are limitless choices of nail diameters and lengths to choose from when designing timber to timber connections, and the temptation for Engineers can be to arbitrarily pick a nail diameter/length that will achieve the desired capacity.
The reality, however, is that 99.9% of nails used in new structural timber to timber connections are fired from a nail gun, so the nails that actually get used on site will be ones that fit in a nail gun, regardless of what the Engineer has specified on a drawing. Given the productivity increase and other advantages that nail guns represent over hand nailing this is fair enough, and we Structural Engineers should make sure what we specify matches the practical reality of site methods and availability of fixings.
For structural work, a 'first fix' nail gun is used (commonly a Paslode gas powered, or battery powered, nail gun), which accept a limited selection of 'collated' round wire nails. These come as strips of nails held together (or collated) by either strips of paper or thin wire. The nails are arranged at an angle (typically 28degrees) to suit the angled magazine of a 1st fix nail gun which allows the gun to get into more spaces and nail at a wider range of angles.
Collated nails are typically available with a smooth shank, or ring shank (for improved withdrawal resistance), and finished bright (no finish) or galvanised for improved corrosion resistance. They may also have a coating that lubricates the nail to improve driving efficiency and/or holding power (withdrawal resistance).
Typical UK collated nail sizes and example uses:
Specialist and other types of nail guns:
Positive placement nail guns - these nail guns feature a special pin tip that locates into the nail holes of joist hangers so nails can be positioned accurately. When the gun fires the pin moves out of the way to allow a nail to be driven in its place. These guns only fire 3.75mm dia. square twist nails of maximum 40mm length.
Coil nail guns - these guns usually only fire nails up to 63mm in length (in the UK, at least) and are most often used for fencing and sheathing applications (the shorter nail length precluding them from general framing applications).
Brad and pin nail guns - brad nails and pin nails are non structural nails used for 2nd fix applications (fitting skirting, architrave, decorative mouldings etc.)
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