King-post truss (standing post)

What is a king-post truss (stojatá stolica)?

A king-post truss, known in Slovak carpentry as stojatá stolica, is a timber support frame built around a single vertical post. The post stands under the roof, carries a horizontal purlin, and that purlin supports the rafters partway up the slope. In Slovak usage the term names one support unit inside a larger roof, not a complete roof on its own.

The English name is an approximate equivalent only. In English practice a king-post truss is normally a complete triangular truss, with a central post rising from a tie beam to the apex. The Slovak stojatá stolica is a post, purlin and brace assembly that sits within a purlin roof system. Both share a central post, but their scope differs, so a Slovak drawing should be read as the post-and-brace frame that holds up the intermediate purlins.

How does a king-post frame carry the roof load?

The load follows a short path. The roof covering loads the rafters, the rafters press on the purlin, and the purlin presses down on the post. The post passes that load to the structure below, while diagonal braces keep the frame from leaning as the roof is loaded.

Member	Where it sits	What it does
Post (stojka)	Vertical, under the purlin	Carries the purlin down to a bearing point
Purlin (väznica)	Horizontal, running along the roof	Receives the rafters and transfers their load to the post
Brace (vzpera)	Diagonal, between the post and the purlin	Keeps the post stable and stops the frame from racking
Foot bearing	At the bottom of the post	Spreads the load into a wall or beam

Each member has a narrow job. None of them can be removed or moved without changing how the rest of the frame behaves, so any change to one member is really a change to the whole frame.

Where must the posts stand?

A post must stand on something that can take its load, which in practice means a load-bearing wall or a beam running in the right direction. A post set on a partition, on an unsupported floor, or in the middle of a room with nothing beneath it has no real support, and the purlin it carries will sag or move. The post position therefore comes from the structural design, not from where the room layout happens to leave space.

The wall plate closes the chain at the other end. The lower ends of the rafters bear on the wall plate along the top of the external wall, and the posts below must line up with walls or beams that can receive their load. A post that lands between supports cannot be fixed with stronger timber. The load has to be moved to a supporting line, which usually means redesigning the frame.

How is a king-post frame different from a queen-post truss?

Both frames support purlins, but their posts sit differently. The king-post frame uses a vertical post, which occupies the centre of the attic. The queen-post truss, known in Slovak as ležatá stolica, uses raking posts that lean toward the roof slope and leave more of the central attic free. That difference is often the deciding factor when the attic is to be used.

Feature	King-post (stojatá stolica)	Queen-post (ležatá stolica)
Post orientation	Vertical	Raking, leaning toward the roof slope
Space in the attic centre	Taken up by the post	Freer, because the posts sit close to the roof planes
Typical fit	Attic kept as storage, or a post position over solid support	Attic to be used, or a layout that needs a clearer centre
Detailing	Simpler, with a vertical load path	More careful joints, because the raking posts carry load at an angle

Neither frame is better in every case. The choice depends on how the attic will be used and where the supports can land.

Why does a king-post frame limit attic conversions?

The post and its braces occupy the space a finished room needs. Headroom, the line of partition walls, and the view across the attic all suffer where the post stands. A designer planning a loft room has to route the living space around the frame, and the post is often a fixed point that cannot be removed without redesigning the roof.

Attic conversion therefore starts with the roof frame, not the finishes. If the room is meant to feel open, a king-post frame is a poor starting point, and the choice is better made while the roof is being designed. The same concern applies to any purlin roof, since its posts and braces are exactly the elements that intrude on the room.

When is a king-post frame a sensible choice?

It suits a roof where the following conditions hold:

• the attic remains storage or service space
• the post position falls directly over a load-bearing wall or beam
• the timber is built and later maintained by experienced carpenters

It is a poor fit where the attic is to become living space, or where no supporting line exists under the intended post position.

Can a king-post truss be removed or altered?

Not without a structural engineer. The post carries roof load, so removing or moving it changes how the purlin and rafters are supported. The engineer checks the existing frame, decides whether a new beam or a relocated post can take the load, and specifies any temporary support needed during the work. A contractor who removes a post on their own judgment can cause the roof to sag, crack the walls below, or fail.

The change may also fall under the notification or permit procedures of Act 25/2025, depending on its scope, so the paperwork should be settled before work starts. If the post sits on a wall that is also being opened, the wall and the post have to be assessed together.

What are the common misconceptions about king-post frames?

• The post is not decorative. It carries load, and removing it is a structural change.
• Strong timber does not make a misplaced post safe. The load path to the foundation still has to exist.
• The English king-post truss and the Slovak stojatá stolica are not interchangeable without checking the design.
• A post that looks lightly loaded may still carry a significant part of the roof.