Brick Jack Arch Flooring

This technical notes is an introduction to brick masonry arches.

Brick jack arch flooring.

The masonry arch is one of the oldest structural elements. The reaction passes through the lower 1 a point of the arch at the skewback. Figure 1 illustrates jack and segmental arches. Many of the different types of brick masonry arches are discussed and a glossary of arch terms is provided.

Unlike regular arches jack arches are not semicircular in form. These floors are formed through constructing brick or concrete arches called jack arches on the lower flanges of mild steel joists. A jack arch is a structural element in masonry construction that provides support at openings in the masonry. The joists are spaced 1 to 1 5 m centre to centre and are supported at their ends either on the walls or on longitudinal girders.

The victorian jack arch floors had larger brick arches around 1 5 m wide with a maximum rise of 20 cm. Brick masonry arches have been used for hundreds of years. Only first class bricks should be used. Major arches are those with spans in excess of 6 ft or rise to span ratios greater than 0 15.

The floor slabs constructed using the steel i beam jack arch system are stable under normal static conditions as the brick arches transfer the gravity loads mainly in compression along the arch. The equilibrium polygon lies completely within the middle of the arch. Used throughout the 19th century for its incombustibility and strength the jack arch was a widespread form of floor construction. Alternate names are flat arch and straight arch.

The construction on jack needs centering of 30 to 40 mm thick segmental piece of timber along with chord length equivalent to the span of the arch and conforming to the soffit. After that centering board is cut slightly at the ends and is made to rest on the lower flange of rsj along with the curved surface upwards. Key brick should be properly and tightly secured in rich mortar. The later 20th century floors however were constructed using smaller brick arches 80 cm 1 0 m wide with an average rise of 5 cm so that a flat surface could also be created for the ceiling by direct plastering.

It was not a flat arch in the us sense of the term rather the jack arch consisted of shallow brick or concrete vaults spanning between iron or steel joists. Before starting the work the rsj should be properly secured in position. Brick jack arch flooring. Instead they are flat in profile and are used under the same circumstances as lintels unlike lintels which are subject to bending stress jack arches are composed of.