Consumables - Nails
A Bit About Nails
Nails are a simple and cost effective way of joing two pieces of timber or similar material. Generally for a first class joint, either joinery, a timber glue, bolts or screws would be used, but the humble nail works and will be with us for a long time to come.
For those interested in such things, the theory behind a nail entering into timber is that it first separates the tiny wood fibres, forcing them into a new formation which will then grip the nail. The nail is effectively held in this 'interference fit' which holds for the inext few hours. Soon after, the moisture in the timber fibres is squeezed out thus lubricating the nail, so for up to a day or so the nail's grip actually becomes less. Over the next day or so, this moisture dries away from the nail, the grip again becomes firmer, and there it stays for the duration.
Straight in Vs Skew & Dove Nailing
Nails can be insertered in two ways. Straight (90 degrees to the surface) or dove nailed (at an angle), dependent upon the two pieces of timber to be joined.
For both types, it is important that the most suitable type and length of nail are used. Lengthwise, generally at least half of the nail should be in the timber being nailed to. For decorative or non-structural timber, this is generally not an issue as a straight nailing approach is used and the piece being nailed is typically thin in comparison to the piece being nailed to.
For a 75mm joist being nailed to a 100mm bearer, the nail would theoretically need to be 150 mm. This is a big nail, but the solution is to skew nail through the side of the beam, at say 60 degrees, halfway up the side of the joist (see figure A below) effectively putting half through the joist and half into the bearer. Skewnailing is of course the only way to nail a vertical beam to a floor beam or bearer, and in the third example below the bearer has been slotted to ensure an even more rigid fit between the two pieces of timber. Additionally this accurately locates the vertical, because skew nailing tends to move the timber being nailed sideways. This slot is easily made with a (tenon) saw and hammer and chisel, or if you have one, a router.
Another advantage of dove and skew nailing is that whereas a piece of timber held by a straight nail can be easily pulled away, two angled nails crossing each other (see examples two, three and four above) will very effectively lock the timber pieces together.
Generally, use the straight approach for non-structural timber, and the dove or skew nail for structural work.
Plain Heads & Lost Heads
Plain heads, by virtue of their larger diameter head, should retain nailed timber better than bullet heads, which can 'pull through' due to the almost non-existent top.
Generally use a lost head where the nail is on the outer piece of timber and needs not to be seen, and a plain head where the timber to be fitted will be covered by wallpaper, plasterboard or a further trim. For instance door frames can be round head nailed to the wall structure, then covered over by the door jams. Round heads are the choice for most structural work, even though skew nailing adds much more strength than the head of almost any nail.
Lost heads can be discreetly hidden by punching them further in with a nail set (or nail punch), then applying a small amount of filler prior to painting. Nail sets are available at many hardware stores, and have a small recess in the end that fits over the nail head. Striking with the same hammer you used for the nail will push the nail in far enough to overfill. Ensure you have the correct size punch for the nails in use, as this results in the minimum size hole, and prevents the punch slipping off the nail.
Construction adhesives, often referred to as liquid nails, are applied as a continuous stream, about 3 to 5mm diameter along the piece of timber to be fitted, then nailed in place to hold until the adhesive sets. These are very useful for skirting boards and decorative panels, and well worth experimenting with.
Normal method of application is to apply a 3mm wide bead near the edges of the piece of timber to be connected, then press the timber in place, remove it again and lay it to rest.
Once the adhesive becomes tacky (sticky to touch, but starting to set) press the piece back in place again and secure with a few well placed lost head nails, which can then be immediately punched in. Full setting will occur overnight and the purpose of the nails is to retain the positioning over that period.
Subsequent removal can be difficult and will often damage one or both of the surfaces, but an alternative is to place a lever behind the board and apply steady pressure. Over a few minutes (sometimes) the afixed piece may move apart.
Below we cover the more common nail types and their general usage.