THE PRINCIPLE OF LIFTING THE LOAD Main components of machine are the cylinders and two threaded winches between two steel beams. Winches are connected with screw bundle concreted into the ceilings, lower bridge of the machines is underpinned by steel pipes. Cylinders lift up the upper bridge together with winches, so the ceiling's bundle is lifted up. Cylinder's length of stroke is 10 cm(clearence). Lifting winches lean against lower and upper bridges with nuts (female screws). When piston reaches the clearence, weight of lifted bundle is loaded over from upper bridge to lower bridge and upper bridge is let back to zero setting. (Nuts on winches are driven by cog-wheels, so that the winch gets into lifting position again.) Lifting is carried out in 10 cm steps so, that this way is also done in controlled parts. Controll Vertical motion on threaded winches is regulated by a controll unit mounted to a rotary motion axle so, that it stops the oil supply of cylinders by 5 mm through microrelays. When all the machines did the 5 mm way it switches the valves for the next pace. With this syncronization one can reach +/- 5 mm clearence on the whole surface of the ceiling. This is necessary to avoid oversizing ceilings for state of lifting. It is also easy to see that syncronization is needed because the loads on lifting achines are different. The load of outer pillars can be one third or one half of inner pillars. The machines lift with different speed and therefore the deformation of ceilings would be very different. To build skeleton-structures in Hungary by Lift-slab technology is permitted by Application Permission nr. ÉMI G-104/89. Lifting machines safety suitability by Hungarian Standard (MSZ 63-3/185) is included in ÉMI-TÜV Protocol/21.05.2004. Structural formation In case of Lift-Slab consruction method the ceilings are usually made as monolith steel-concrete structures at spot. In general 4.5-6.0 m pillar's span is optimal to build living houses of individual appearence. In this case it is unnecessary to lighten the structural concrete ceilings because in 18-20 cm thickness they meet statical and physical requirements, too. In case of buildings with bigger span (hospitals, office and commercial buildings etc.) it can be reasonable to make lightened ceilings for decreasing self-weight and inclination. In time-honoured solutions we often applied lightened elements and granulate moulding. This made possible that the weight of a 30-35 cm thick ceiling (necessary for 9.-12.0 m span) equials the weight of a 15-20 cm thick solid concrete ceiling. For assembling ceiling's steel structures we generally use ribbed reinforcing steel and distributing ironwork in welded reticulated make-up. By this way we