Horizontal structures
The following paragraphs describe the material and technological processes of historical horizontal structures.
Vaults
The vault is an arched structure composed of brick or stone elements. The vaults were usually performed by placing the archstones to the mortar on wooden falsework so that the joint between stones directs to the center of the arch. In the joint of the vault there is only compressive stress, which allows to design vaulting of a large span. The disadvantage of the arches are oblique forces in the arch abutment.
Semi-circular (barrel) vault
Used since the Pre-Romanesque time to the early 20th century. It has a generally semicircular arc shape deposited on the longitudinal walls. Initially used for smaller spans. Later larger spans (span 10m Knížecí Palace at Prague Castle from the 12th century, span 30m at the Church of St. Peter's in Rome from the turn of the 15th and 16th centuries). The barrel vault with a full arc is often used in the Renaissance and Baroque.
Fig.: The barrel vault with lunette, 01-lunette.
Groined vault
Frequently used in medieval buildings. Groined vault is created by intersection of two barrel vaults. Made up of bricks or stone blocks, over time with salient ribs (transverse and diagonal ribs). Load stress (pressure) acting to the ribs.
Fig.: Groined vault, 01-transverze rib.
Domical vault
Domical vault is created by intersection of two barrel vaults (at the intersection are formed so called “hollow ribs”). Domical vault requires supports around the whole perimeter. Made both at a regular and irregular platform. The tension pass from ribs to supports. The ribs had to be without any joints, so there were used a modified stone ribs or modified bricks.
Fig.: Domical vault, 01- vault head, 02-transverze rib.
Trought vault
Carried out over the oblong rooms (like barrel vault), with faces of vault closed by part of the barrel vault. The contact of longitudinal and transverse layers is very important.
Fig.: Trought vault
Dome
Are formed by rotating a half-circle or half-ellipse around a rotating axis. Large domes were arching with vertical and horizontal ribs and between the ribs vaults with a small span were made. Trimming dome over a square or rectangular platform creates Segmental sail vault („česká placka“), widely used in the Czech Republic in Baroque period.
Fig.: Dome and Segmental sail vault (so called „česká placka“).
Timber intermediate floors
The advantage of timber intermediate floors is their easy feasibility and low weight, while the disadvantage can be lower fire resistance, possibility of infestation by wood decaying fungi and wood-destroying insects. Timber intermediate floors are not suitable for wet areas.
Rounded timbers
Carried out from round timber logs of smaller cross-sections, closely engaged and joint with pins. The top roof plates were made of large logs, which have a good thermal insulation and a high bearing capacity.
Fig.: Rounded ceiling, S01- wooden joists, straw with cob, 02- pin.
Girder floors
Girder floor consists of timber joists (beams, girders) for a certain axial distance at which a deck (boarded or planked) is made. Above the deck filling is made, usually for fire and acoustic reasons (80 to 120 mm thickness of the slag, coarse sand, or the construction of “rum” - waste) and wood floor on girders. Ends (gridiron) of joists were stored in pockets in the walls (save 100 to 250 mm) on a wooden sole piece (thickness 30 to 50 mm) so that between the masonry facing and joist end was an air gap (20 to 40 mm thick). To increase spatial rigidity of the building (to ensure opposite walls against collapsing from the upright position) joists were often connected with perimeter wall with so called grid clamp (steel rod). Girder clamps were made for each third or fourth joist.
Fig.: Girder floor, S01 - boarded (or planked) deck, filling (scoria), floor carrying beams, floor boarding, 02 - wooden beams (by span 160x200mm to 240x300mm approx).
To reduce the thickness of the floor, but to keep the minimum necessary layer of filling (fire and acoustic reasons), the deck of girder floors was embedded. Beams carrying the flooring were then carried out parallel to the joists.
Fig.: Girder floor, S01 - boarded (or planked) deck, filling (scoria), floor carrying beams parallel to the joists, floor boarding, 02 – bearer of the deck, 03- floor carrying beam.
To increase fire resistance girder floors were made with boards layer (thickness 18-25 mm- in Czech called “Kopinky”) and plastered reed matting. Large deflections of girder floors caused cracking of plaster ceiling. Therefore the ceiling was often carried out on a separate ceiling joists (in Czech so called “rákosníky”).
Fig.: Girder floor, S01 – girder floor with the construction of flooring, 01 – ceiling joist (so called „rákosník“), 02- plastered reed matting on boards layer.