Queen-post truss

What is a queen-post truss (ležatá stolica)?

A queen-post truss, known in Slovak carpentry as ležatá stolica, is a timber roof frame in which inclined posts run roughly parallel to the rafters and carry the purlins from below. The lower ends of the posts are tied together by a horizontal straining beam, which holds the frame in shape and takes the outward push of the roof. Because the posts lean along the roof slope rather than standing upright in the middle, the centre of the attic stays free.

The English label needs a caveat. In British and older English-language texts, a queen-post truss normally has two vertical posts standing on a tie beam, so the English term is only an approximate equivalent of ležatá stolica. The Slovak form is closer to a raking-post frame. When a designer or carpenter uses the Slovak term, check the section drawing for inclined members rather than relying on the English name.

How does a queen-post truss carry the roof load?

The load follows a short chain. The roof covering loads the rafters, the rafters bear on the purlins, the purlins rest on the raking posts, and the posts pass their load down to the straining beam. The straining beam then carries the frame to the supporting walls. No single timber has to span the full width of the building, which is the same principle as the wider purlin roof system: each link covers a shorter distance than the whole roof would.

Three members do most of the work:

• Purlins, horizontal members that catch the rafters partway up the slope. The purlin entry covers their types.
• Raking posts, inclined members parallel to the rafters that carry the purlins down.
• Straining beam, the horizontal tie at the foot of the posts that resists the outward thrust and stops the walls from being pushed apart.

Joints do much of the real work in a timber frame, so the condition of the joints is the first thing to inspect in an existing roof. The wider family of frames that uses purlins is described in the purlin roof system article.

How does the raking-post form differ from a vertical queen-post?

The table sets the Slovak form beside the vertical queen-post often described in English texts. Both leave the middle of the attic clear, but the geometry differs.

Feature	Vertical queen-post (English texts)	Raking-post queen-post (ležatá stolica)
Post direction	Vertical	Inclined, parallel to the rafters
Where the posts stand	On the tie beam	Feet tied by the straining beam, heads carry the purlin
Clear space in the attic	Open between the two posts	Open across the centre, with the posts along the sloping sides
How it reads on a drawing	Upright members	Inclined members that follow the roof pitch

The drawing decides which frame you have. Two inclined members do not by themselves make a ležatá stolica, and the joint geometry matters as much as the angle.

When is a queen-post truss the right choice?

It is most often found in historic roofs and in larger roofs, where a central frame of upright posts would take up too much of the attic. It is also a common choice when an attic conversion is planned, because the clear centre gives usable headroom under the ridge.

The posts still take up space along the sloping sides, so the gain is a clear centre rather than a clear space at the eaves. Headroom near the walls stays limited, and the layout of any room, wall or dormer has to allow for that.

A queen-post frame is not automatically the cheaper option. It needs skilled carpentry, and a designer has to check it for the site's snow and wind loads before the timber sizes are fixed.

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

The king-post truss (stojatá stolica) is the other classic timber frame in Slovak practice. The two are easy to confuse because both sit in the same roof, but the central arrangement is what sets them apart.

Feature	Queen-post truss (ležatá stolica)	King-post truss (stojatá stolica)
Main support	Inclined posts carrying the purlins	One vertical post on the centre of the tie beam
Centre of the attic	Free	Occupied by the central post
Typical use	Historic and larger roofs, attic rooms	Smaller spans and simpler roofs
Bracing	The straining beam ties the feet of the posts	Braces hold the central post steady

The king-post truss has its own entry, king-post truss. Choosing between the two is a design decision about attic use, span and loads, and it should be settled before the roof is drawn.

How does a queen-post truss compare with a prefabricated roof truss?

A prefabricated roof truss is a factory-made triangulated frame, usually of nail-plated timber, delivered and lifted into place. Its web members sit inside the roof void, which is why it suits roofs without a usable attic. A queen-post truss is usually framed from individual timber members, often on site.

Feature	Queen-post truss	Prefabricated roof truss
How it is made	Framed from timber members, often on site	Factory-made, delivered and lifted into place
Attic space	Clear centre for use	Web members fill the void, so the attic is not usable
Labour on site	Skilled carpentry	Erection crew, with fewer joints cut on site
Changes during the job	Can be adjusted while framing	Fixed to the factory design

The types of traditional and prefabricated roof structures are compared in the roof truss article.

What are the common misconceptions about the queen-post truss?

• "Any roof with posts in the attic is a queen-post truss." The name depends on the geometry. Vertical posts, inclined posts and the king-post arrangement are different frames, and a check of the drawing settles the question.
• "The open centre means the frame is light." The open centre changes where the members sit, not how much load the roof carries. The straining beam and the posts still have to be sized for the loads.
• "It can be altered freely." Removing or cutting a post or the straining beam changes how the frame carries load, so any change should be checked by a structural engineer first.