Initially the Russian builders laying the floor used design, named "Bridge": the board according to this method of laying were placed directly on the ground, without any intermediate materials. It was the first wooden floors. But on the first floor houses a "bridge" accumulated moisture from the ground, hence, the tree relatively quickly become useless, and the floors had to be changed. Pay attention to this, the builders changed the technology of laying floors. Boards were laid on the beams, so-called "baggage" who later received another name – "lag." In order to "treasure" does not rot on contact with the ground, they were placed under the base of stone, brick, after a time lag began to lay on the metal beams. Such Laying edging board called "bridge to treasure", and design in general is called "scaffolding." If the luggage is not installed on the ground, and erected on the "stage", then this design was called the dais.
Both of these Construction began a kind of "black" sex. Laghi stretched from wall to wall. Their end parts, they were not supposed to touch the walls, thereby avoiding the destruction tree fungus. Most often lags mounted parallel to each other. At the same time drawing attention to the fact that the underground space is properly ventilated and not too wet. In intervals often poured rubble or well dried sand. Level backfill often did not reach the upper edge beams, which provide good ventilation of the underground structure. Already in ancient times was used for ventilation to prevent the development of mold.