If you are working on a big project, it may be necessary to join two pieces of timber
together to gain a longer length. Smaller projects also often require a section of wood
grafting. There are several methods of joining timber, dependent on the strength and
finish required.
Bolted joint
For a strong face to face joint use coach bolts in conjunction with timber connectors (metal
washers with toothed edges). Drill three holes along the centre of the sides of both timbers,
aligning with the adjoining timber. Use the timber connectors between the two pieces of
timber to be joined. Insert the bolts making sure the timber connectors are on the bolts
when pushed between the two timbers. Use washers and nuts at the other end to tighten the
joint. The timber connectors bite into the wood as the joint is tightened, increasing the
strength of the union.
Joining plates
If the two timbers to be joined are meeting end on end, use two wooden plates to hold the
union together like a sandwich. The two wooden plates must be strong enough to support the
join. Measure the width of the timber to be joined. Use timber plates that are 4 times
longer than that width. The timber plates should be the same width as the timber but half
its thickness. Glue all the surfaces together before drilling holes in the construction and
either screw or coach bolt the whole section together in strategic points staggered across
the surface of the plates.
Lapped joint
This type of joint is more suitable for lengthening lighter structures and is the easiest
method of joining two timbers. Measure the timbers and mark the halfway positions on each.
The laps should be cut to half the thickness of the timber, one cut reflecting the other in
the second timber. The two shoulders made must butt exactly against the end of the joining
pieces. Glue all the surfaces together before drilling holes in the construction and screw
the sections together in strategic points staggered across the surface grain to avoid
splitting.
Scarf joint
This type of joint is only suitable for lengthening lighter structures such as in cabinet
making. For the greatest strength, make the scarf length 8 times longer than the width of
the timber. Measure the timbers and mark the scarf positions on each. The splayed faces
must be measured, cut and planed accurately to perfect the bond. The faces must butt exactly
together. Glue all the surfaces together and screw the sections together for added strength.
Splayed lap joint
This type of joint is a variation on the lapped joint. The difference is that the lap is
cut in the thickness of the timber instead of the width of the timber. The splayed lap
joint is suitable for joining timber directly onto a joist or timber wall, giving it extra
support. It is suitable for use when the timbers need to keep a straight edge in order to
be used to support hardboard or chipboard sheeting. The length of the joint should be equal
to the width of the timber. To help resist the chance of the joint being pulled apart,
cut the splays along the grain of the wood. Check that they butt together exactly before
securing. Nail the lower section of timber diagonally through to the joist or timber wall.
Butt the joining length of timber into position and nail it diagonally through the top.
Spliced joint
This type of joint is used when appearance is of prime importance, particularly in furniture
repairs. Use a fine tooth saw to cut a 'V' shape in one section of wood. The joining
section must be cut and planed to make a perfect fit if the repair is to be successful.
It is worth spending time getting the exact fit before fixing the two pieces together.
When ready glue and clamp the pieces together until the glue sets. If the join is in a
vulnerable location, screws can be used to add extra strength.