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1950-51 Theatre Catalog, 9th Edition, Page 131 (111)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 131
Page 131

1950-51 Theatre Catalog, 9th Edition, Page 131

temperature is favorable. Through this curing process, the internal structure of the concrete is built up to provide strength, resistance to wear and watertightness. Floor finishes present such a large surface area that loss of moisture through evaporation takes place rapidly unless measures are taken to prevent such evaporation. Rapid drying not only stops the chemical reactions, but may cause dusting and also cracking of the surface due to shrinkage taking place at a time when the concrete has little strength.

To prevent drying out, water for curing should be applied to the new concrete as soon as this can be done without marring the surface. It should then be kept wet with sand or burlap or the moisture should be sealed in by covering the floor with waterproof paper or a membrane curing compound. The longer this curing period can be extended, the stronger, harder and more impervious will be the concrete. The curing period should run one or two weeks at least. , Special attention should be given areas near radiators or other sources of heat, to prevent evaporation during the curing period.

Construction Methods

Floor finish may be placed after the base has hardened or while the base is plastic. The first method is preferred, as the finish is then put on after other building operations have been completed and, therefore, is less likely to be damaged. Better control of the water content is also obtained. Good results can be secured in either case if the base is properly prepared.

It is essential that the base be of good quality to prevent the finish from pulling away from it. The quality in iioors above ground is usually governed by structural requirements.

Preparation of Hardened Base-In two-course construction, a good bond between the base course and wearing surface is essential. It is readily accomplished by attention to the preparation of the base to receive the topping. The wearing course for heavy-duty fioors such as are needed in theatres should be placed after the base has hardened.

The base course in new construction should be brought to grade not less than 1 in. below the finish grade. When it has partially hardened so that it will retain the impression of a broom, it should be brushed with a stiff-bristled broom, removing all laitance and scum. The brooming should expose some of the aggregate and score the surface to provide mechanical bond for the wearing course. The base should be wet-cured for at least 5 days, unless high earlystrength portland cement or concrete is used; this should be cured at least 2 days and protected from grease, plaster, paint, or other substances which would interfere with the bond.

Immediately prior to placing the finished topping, the base course should be thoroughly cleaned by scrubbing with clean water and a stiff brush. Foreign substances not removed by the scrubbing should be chipped off. If the base has been allowed to dry out, it should be thoroughly wetted; preferably kept wet overnight.


A NEARLY COMPLETE AUDITORIUM FLOOR shows the concrete slab in place with the proper depression for aisle carpeting. Careful grading has resulted in a sloped floor that will assure a good view from every seat. Choirs will shoglly be installed securely with expansion bolts.

There should be no pools of water on the surface, however, during the next operation. Thoroughly broom into the wet surface a slush coat of cement and water mixed to the consistency of thick paint, brushing out well to avoid too heavy a layer, The topping should then be placed immediately to avoid drying of the slush coat.

Resurfacing a BaseeAlthough properly proportioned concrete, carefully laid and cured, gives a floor surface maximum wear resistance, some theatre

floors are occasionally improperly built.,

These may become so badly pitted and worn that it becomes necessary to provide an entirely new surface.

On resurfacing jobs where the old fioor level must be preserved, the old concrete must be cut away to a depth of 1". Where a new topping is to be placed directly over an old one without chipping off the old surface when the iioor will stand the added load and raising the floor level is not objectionable, the new topping should be at least 2" thick and reinforced with wire mesh, weighing not less than 30 lb. per 100 sq. ft. and placed approximately in the middle of the concrete. The surface of the old floor should be roughened with a pick or grinding tool. All loose particles: grease, oil, paint or other materials must be removed. Grease and oil may be removed by scrubbing with gasoline. Paint must be chipped of'f. Sandblasting is sometimes helpful, and scrubbing with a 10 per cent muriatic acid solution or with strong washing soda solution is helpful in removing dirt and other substances.

After the slab has been cleaned, it should be saturated overnight. A slush coat of cement and water should then be broomed into the surface just prior to placing the concrete for the topping.

Integral Finish PreparationeWhen the finish is to be placed on the base before the latter has hardened, it is important to use a mix in the base

which will not permit water to collect in puddles on the surface. If this occurs, the wearing course will absorb the excess water, greatly reducing the durability and strength of the finish.

The mix for the base, therefore, should be adjusted if necessary to prevent water gain on the surface. Any water that collects on the surface of the base should be removed before the wearing course is applied. The base course should have stiffened sufficiently so that footprints will not be made by the workmen when they are placing the topping.

Placing and Compacting ToppingeThe exact procedure to be followed in placing and compacting the topping will depend on whether or not a mechanical doat is to be used. The concrete may be spread with shovels and ordinary garden rakes to a fairly uniform level, slightly above the finished grade, and compacted with tampers or rollers or both. It should then be struck off to grade, floated with mechanical or wood floats and finally troweled to the desired finish.

Tamping or RollingeThe concrete should be compacted throughout its depth by tamping with iron tampers or rolling with weighted rollers. This gives a hard, compact topping essential for a durable floor. When rollers are used, particular attention should be given the areas around columns and at walls where it is difficult to make rolling effective. Any areas that are not reached by the roller should be thoroughly tamped.

ScreedingeScreeding is the operation of striking off the concrete to the proper level. When using the mechanical float some contractors place small precast concrete blocks in mortar at intervals of 8 to 10 ft. in both directions on the base. A surveyorls level or straightedge and spirit levels may be used to place these at the proper level.

After the concrete has been spread and tamped or rolled, a straightedge is

1950-51 Theatre Catalog, 9th Edition, Page 131