Preblended Cement Based Stucco Basecoat
Standard (SU-01)


SPEC MIX® Scratch and Brown Preblended Stucco is a dry, preblended cement-based product designed to be used as the scratch and/or brown coat in a three-coat stucco application. This product also can be used as the first coat in a two-coat application for exterior stucco applications. The final wall system will produce a nonload-bearing, aesthetically pleasing exterior veneer or interior finish on concrete or masonry walls, stud walls or metal buildings.

SPEC MIX Scratch and Brown Preblended Stucco is produced under strict manufacturing standards, and complete quality control measures are implemented with each batch. A digital printout displaying the proper proportions per batch may be kept as a permanent record. Each SPEC MIX® manufacturer certifies that SPEC MIX® stucco products are designed to meet the project specifications and applicable ASTM standards.

SPEC MIX Scratch and Brown Stucco can be installed over framed wall construction that includes a solid backing: including Fiberboard, Gypsum Sheathing and Wood Based Sheathing. SPEC MIX Scratch and Brown Stucco can also be applied over Concrete and Masonry.

Product Features

• Custom blended sand gradation that increases the walls flexural strength while reducing cracking and crazing
• Computer batched for consistency and performance that is unmatched by traditional field mixed stucco
• Provides excellent workability and finishing properties for the applicator over a traditional field-mixed source
• Can be applied over framed wall construction that includes a solid backing such as fiberboard, gypsum sheathing and wood based sheathing.
• Can also be applied over concrete and masonry substrates

Scratch and Brown Estimated Yields
Package WeightFBC ThicknessCoverage
80 lb (36.2 kg)3/8" (9.5 mm)20 - 24 ft² (1.8 to 2.2 m²)
80 lb (36.2 kg)1/2" (13 mm)15 - 18 ft² (1.4 to 1.7 m²)
80 lb (36.2 kg)3/4" (19 mm)10 - 12 ft² (0.9 to 1.1 m²)
3,000 lb (1,360.7 kg)3/8" (9.5 mm)750 - 900 ft² (to to 84 m²)
3,000 lb (1,360.7 kg)1/2" (13 mm)560 - 675 ft² (52 to 63 m²)
3,000 lb (1,360.7 kg)3/4" (19 mm)375 - 450 (35 to 42 m²)
Depending upon surface conditions, workmanship and technique as as waste, square foot coverage may vary. Above are only estimates for 80 lb (35.2 Kg) and 3,000 lb (1,360.7 kg) coverage rates.

Scratch and Brown Fiber Base Coat Installation/Application

SPEC MIX Scratch and Brown Preblended Stucco is designed for use over galvanized, expanded metal lath or solid base surfaces such as masonry or precast concrete. The material can be hand applied or machine sprayed. Installation of stucco over these surfaces shall be in accordance with ASTM C 926, and all applicable building codes. Dampen all surfaces to receive stucco prior to application. An expansion joint should be installed at dissimilar materials. Stucco shall be used and placed in final position within one hour after initial mixing. Variation of water content and retempering will affect strength, consistency and uniformity. SPEC MIX products must be kept dry, covered and protected from weather and other damage.

Sizes and Equipment

SPEC MIX Scratch & Brown Preblended Stucco is available in 80 lb (36.2 kg) packages for easy hand loading or in 3,000 lb (1,360.7 kg) reusable bulk bags to be used with the various SPEC MIX silo systems. When using the silo system, once the bulk bags of stucco are delivered to the project site, the portable silo is loaded with a jobsite forklift and the product is dispensed into a mechanical batch mixer.


WEAR IMPERVIOUS GLOVES, such as nitrile.
1. Add approximately 1.2 to 1.5 gallons (4.5 to 5.7 liters) of clean water into the mixer for each 80 lb (36.2 kg) bag.
2. Slowly pour the contents of the bag(s) into the mixer.
3. Mix for 5 minutes until a firm, workable consistency is achieved. Avoid over mixing as this may affect the integrity of the finished product.
4. If more water is needed, add small amounts at a time and continue to mix until the desired consistency is achieved. Do not exceed a total volume of 1.75 gallons (6.6 liters) of water for each 80 lb (36.2 kg) bag.
5. Keep mixing times and procedures the same every batch. Over mixing may entrain air, which can adversely affect plastic and hardened stucco properties. Prepare only as much mix as can be applied in one hour.

Stucco must be water cured with a fine mist once it has achieved final set. Care must be exercised when moist curing to avoid erosion damage to plaster surfaces. Spray the wall periodically for 48 hours. During hot and dry conditions, additional precautions may be necessary, including more frequent spraying or the erection of barriers to deflect sunlight and wind.