> > > >

1950-51 Theatre Catalog, 9th Edition, Page 135 (115)

1950-51 Theatre Catalog, 9th Edition
1950-51 Theatre Catalog
1950-51 Theatre Catalog, 9th Edition, Page 135
Page 135

1950-51 Theatre Catalog, 9th Edition, Page 135

of 1 part of portland cement and 2 parts of coarse, clean sand is dusted on the unhardened concrete in a uniform layer not over 1A;" thick. When the dry materials have absorbed moisture from the slab and the concrete has hardened enough to allow finishing, it is doated and troweled to unite the dust coat with the base and give an even surface free from air holes, depressions, and other blemishes. The door should be protected and cured as recommended for other types. This dust-coat method of finishing should not be used for uncovered doors Where the finish would be directly subjected to traffic.

Wood. Linoleum, Rubber. and Cork Tile

When wood, linoleum, rubber or cork tile is to be used, the concrete must be thoroughly dry before cementing the surfacing material into place. Moisture, even in very small quantities, will eventually lead to the decomposition of the adhesive. A simple test to determine Whether or not the concrete is dry may be made by laying pieces of linoleum at several places on the door, weighting them down so they will have uniform contact with the surface. If, after 24 hours, moisture appears on the underside of the linoleum, it will be necessary to let the concrete dry further before cementing the covering to it. The direc< tions of the manufacturer of the materials being used should be followed.


Floors to be covered with carpet require wood nailing strips, usually around the border of the area. These should be well seasoned lumber, dressed to 1"x2" and embedded in the unhardened concrete. Special snap inserts are sometimes embedded in the concrete instead of nailing strips. In this case fastening devices are attached to the underside of the carpet.

The surface of the concrete door should be screeded, troweled dush with the tops of the wood strips, and should present a smooth, even surface. It should be cured and allowed to dry before placing the carpet. Pads or cushions under the carpet prolong the life of the carpet and assist in producing soundproofness.


Concrete doors should be accorded their rightful share of attention in any theatre maintenance program to insure their continued high quality of service and durability. Although relatively little expenditure of time, effort, and money is required to keep concrete doors in first-class shape, it is vital to give them whatever repairs, cleaning, and treatments are needed.


Floors are sometimes so poorly built as to be wholly inadequate for the service intended. In such cases it is advisable to remove the defective top surface and replace it with a new one in accordance with the suggestions given previously. Failure to observe some fundamental requirement in construction may result in certain defects which often can be corrected by proper treatment or repairs.


LINOLEUM OR SIMILAR FLOOR COVERINGS may be easily applied to concrete subiloors, but they must he finished to a true. even surface and should be thoroughly clean and dry before application.

Dusting # Floor finishes that dust under service may usually be improved by a hardener treatment. Whether a hardener treatment will entirely stop dusting will depend on the construction methods used and the resulting condition of the surface.

Where there is a thin layer of soft, chalky material at the surface, this may often be removed with pads of steel wool attached to a scrubbing machine. After removal of this material, the surface should be thoroughly cleaned, allowed to dry, and one of the hardener treatments applied. In other cases, it is necessary to grind the surface. before treatment.

CrackingeCracks in concrete doors may be classified as (1) structural cracks originating in the base and extending through the finish, and (2) cracks confined to the wearing course. The latter may extend through the wearing course, or may be of a superficial nature, ordinarily called tthair cracks" or ticrazing."

Structural cracks may be caused by shrinkage, temperature changes or settlement. If there is recurrent movement, there is little that can be done other than to keep them filled with a mastic material. Crazing cracks may be removed by grinding if they are not too deep. The only other method of removing them is to remove the affected area and replace it with new material.

In many cases cracks may be filled with varnish or resin. Although they will remain visible, accumulations of dirt and leakage will be prevented, Artificial resins such as Cumar (available through paint and varnish manufacturers) may be used. This should be powdered and dissolved in a suitable solvent such as xylol, in the approximate proportions of 6 lb. of resin per gallon of solvent. A varnish-like material is produced which can be run into the cracks. Cement may be added to make a thicker solution for wider cracks.

In patching concrete doors, the old wearing surface should be chipped off to a depth of at least 1". The roughened surface should be thoroughly cleaned of loose particles and should be saturated with water for several hours before placing new concrete. The area surrounding the patch should be wetted also.

Roughened Floors-Floors that have been improperly constructed may become roughened under service, or pitting may occur due to heavy impacts. Often such doors may be put into satisfactory condition by grinding off the roughened surface and will give good service for many years. On the other hand, if the concrete is of such poor quality that the surface will soon become roughened or pitted again, it would be more economical to resurface it with the proper quality of concrete.

Equipment Attachment-Theatre seats may be rigidly fastened to concrete doors with expansion bolts. For satisfactory results the concrete must be of such quality that it will resist the stresses developed by the equipment to be attached. The wearing course should be constructed as recommended previously. If large bolts extending into the base course are used, the base course should be well proportioned with not over 6 gal. of water per sack of cement to provide a good grade of concrete.

The usual procedure is to mark the location of bolts on the door after it has hardened and cured, then drill the holes to the proper depth for insertion of the expansion shells.


Properly constructed concrete doors will require little maintenance other than cleaning. Periodic cleaning is essential to durability, as grit and dirt on doors subjected to considerable tradic will be ground into the finish and accelerate the rate of wear.

1950-51 Theatre Catalog, 9th Edition, Page 135