allen RS844, Operations & Parts Manual, Page: 30 / 130

057625 - 10/2012
SECTION 2
OPERATIONS
Page 2-4
2.1 General Information (continued)
Wood forms are not a preferred method of screed support. Because of the concentrated bearing loads
by the screed, wood is not a good support material. Nominal 2 X 1-1/2 No. 2 Douglas Fir is calculated
to support a maximum of 1000 lbs. (453 kg.). The grain could crush and splinter causing level variations
and potential failure. 4 X 3-1/2 lumber for edge form shoud be acceptable.
Check with city and state civil engineering regulations regarding the type and size of lumber used for
edge forms.
Screed rails and supports, independent of slab edge forming is the perferred method. Due to strength,
deflection and traction considerations, 2.5” X 2.5” X.1875 (3/16-inch) wall structural steel tubing with
adjustable support spacing is recommended.
Standard deflection with 3/16-inch wall tubing thickness for the above reference configuration is 1/16-
inch for every 3 ft. (1.2 meters). Refer to standard material charts for other configurations.
Paving forms with 90° lip-edge at bottom with stake pockets is preferred. If soft or unleveled subgrade is
encountered, a 2X bearing pad and/or shims should be used under the steel forms for additional bear-
ing support. Depending on slab thickness and subgrade, forms may require diagonal bracing.
These recommended form and rail specifications are provided to illustrate the application and are not
intended to superceed or replace any city or state civil engineering procedures and or specifications.
AEC will not be responsible for the improper application of the RS-Series Roller Screeds.