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Frequently Asked Questions
Why use a concealed hanger?
Because nothing is visible once the joint is closed.
The connector sits in recesses machined into both members.
That suits exposed timber frames, joinery and architectural work.
A galvanised bracket would be unacceptable in those settings.
It is chosen for appearance rather than for capacity.
The structural performance is a requirement to be met, not the reason for the choice.
What does it cost in return?
Machining accuracy, inspectability and, often, disassembly.
Recesses must be accurate in position and depth in both members.
That generally means a jig or CNC preparation rather than site work.
Once assembled nobody can see whether it is seated correctly.
Some systems are demountable and many are not.
Taking apart a joint not designed for it usually damages the timber.
How is a concealed connection inspected?
It largely cannot be, once closed - which changes how it must be recorded.
Whether every fastener went in is invisible afterwards.
So is corrosion, seating and any damage during assembly.
Photographic records during assembly are worth taking on anything structural.
Some schemes require inspection before closing.
Conventional hangers can be checked at any time, and that is a real advantage they hold.
Do they perform better in fire?
Frequently yes, and it is a genuine reason to specify them.
Steel loses strength quickly when heated.
A connector buried in timber is insulated by the char layer forming around it.
Surface brackets are exposed directly to the fire.
That makes concealed connectors attractive in exposed structural timber.
Fire resistance requirements and how they are demonstrated differ between markets.
Does the timber species matter?
More than with surface-fixed hangers.
The load transfers into a small area of the timber's interior.
Density and species therefore govern what the joint can develop.
Published tables are species-specific for that reason.
Engineered products such as glulam and LVL have their own figures.
Applying a softwood figure to a different species is not a safe substitution.
Can they be installed on site?
Assembly can be, but the machining generally cannot.
Recesses are prepared in the shop with a jig or CNC.
Site routing rarely achieves the accuracy required.
Members then arrive prepared and are brought together.
That makes setting-out errors expensive to correct.
Trial assembly before delivery is common on complex frames.
Are the fasteners still critical?
Yes, and their inaccessibility makes getting them right first time more important.
Published capacity assumes the specified fastener in every position.
Many systems use proprietary screws or dowels rather than nails.
Substitution is not permitted without invalidating the rating.
Nothing can be corrected once the joint is closed.
That is the practical difference from a surface hanger, where a missed nail can be added.