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Frequently Asked Questions
What does a post cap do?
It transfers the beam's load down into the post, concentrically.
Without one, the beam relies on toe-nails or on nothing.
Any eccentricity tries to push the beam sideways off its support.
A cap locates the beam over the centre of the post.
Load then travels straight down the post's axis.
It also ties the two members together against uplift and lateral movement.
Why does concentric bearing matter?
Because off-centre load puts bending into a member designed for compression.
Posts are considerably weaker in bending than in axial load.
Eccentric loading therefore reduces capacity substantially.
It can also split the post at the top.
The cap holds the beam where the post can carry it.
That is a structural function rather than a locating convenience.
Which configuration do I need?
Whichever matches the geometry of the actual joint.
A single beam landing on a post takes one form.
Two beams meeting over a post take another.
A beam continuing across a post takes a third.
Ordering by member size alone can produce a cap that will not suit.
Identifying the arrangement first narrows the choice quickly.
Can I pack out a loose fit?
No - the bearing area and fastener positions assume the stated dimensions.
A cap is made for a specific post and beam width.
Packing with offcuts is not an equivalent connection.
It changes how load reaches the timber.
It also moves fasteners away from their designed positions.
Ordering the correct size, including for dressed rather than nominal timber, avoids it.
Where does uplift resistance matter most?
In exposed structures where gravity is not doing much holding.
Pergolas, carports, verandas and open frames are the typical cases.
Wind can lift a beam off a post it was only resting on.
The cap ties the two together against that.
Uplift requirements come from the site's wind loading.
In exposed and coastal locations the figures are substantially higher.
Do caps have to be visible?
In exposed structures they usually are, which is why decorative patterns exist.
Appearance frequently matters alongside capacity.
Concealed patterns hide within the joint where the look matters more.
Those carry the same machining and inspection trade-offs as any concealed connector.
Powder-coated and architectural finishes are available.
Corrosion specification still follows the exposure rather than the finish.
Does the fastener rule apply here too?
Fully - the schedule carries the rating on both the post and the beam side.
Every specified hole takes the specified fastener.
Filling only the accessible side gives that side's capacity.
Fixing sequence matters once the beam is in place.
Planning access before lifting the beam makes it achievable.
A cap fitted with half its fasteners has no published capacity at all.