Apex Multi Underlayment
Apex Multi is a UL approved Limestone based Cementitious underlayment designed for use on both new and existing subfloors, providing a durable, high-strength surface ideal for various flooring systems.
This versatile underlayment is perfect for both residential and commercial applications, offering superior performance in terms of compressive strength and sound attenuation. With a high strength formula, it achieves a compressive strength range of 2750 – 3600 psi (19 – 25 MPa) and is highly resistant to surface abrasion, making it suitable for areas with high foot traffic. The underlayment’s crack-resistance ensures a stable base for all types of floor coverings, including tile, carpet, vinyl, and hardwood.
Apex Multi Cement-Based Underlayment is especially effective in multifamily housing, commercial environments, and renovation projects, offering both enhanced soundproofing and fire-resistant properties. Its quick drying time minimizes downtime, allowing flooring installations to proceed quickly after application. Whether used in new construction or renovations, this product provides a reliable, long-lasting base for all flooring systems.
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- High compressive strength and impact resistance
- Suitable for use in wet areas and high-moisture environments
- Provides improved sound attenuation properties
- Ideal for multi family wood frame and concrete construction
- Recommended installation thickness of 3/8” to 3” in a single pour
Installation
Apex Multi Floor Underlayment is mixed with approved sand and potable water at the job site to yield a lightweight underlayment that weighs approximately 7.5 lbs./sq. ft. at 3/4 in. (19 mm) thickness and has an approximate dry density of 120 lbs./cu. ft. Apex Multi must only be installed by a trained and licensed Apex Multi applicator.
The structural subfloor should be adequate to withstand designed loads with a minimum deflection criterion of L/360.
During the entire installation process, ensure the building is fully enclosed, with the temperature maintained at a minimum of 50 °F (10 °C) for optimal curing conditions. Adequate ventilation is essential to ensure even drying of the applied underlayment, which typically occurs within 5–7 days when applied at a 3/4 in. (19 mm) thickness.
Protect the underlayment from excessive trade traffic (e.g., equipment, heavy tools, carts) by placing plywood or other protective materials over it. Exposure to heavy weight during the curing process can delay drying in those areas, so ensure these sections are thoroughly dry before installing flooring materials.
Concrete Subfloor Preparation
Mechanically prepare the substrate to remove surface contamination and laitance including any concrete sealers or curing compounds and provide an open textured surface. Substrate must be dry, clean and free from loose materials, dirt, oil, grease and all forms of contamination.
Use a suitable bonding agent to ensure solid bonding of the underlayment to the substrate. If the substrate is >85%RH, then a Moisture Mitigation Product will be required.
* If the substrate is <85%RH, then an acrylic primer will be required.
*Always comply with the Moisture Mitigation manufacturer’s guidelines. Respect existing expansion and control joints, and ensure they are properly accommodated during installation.
Wood Subfloor Preparation
Wood subfloors must be structurally sound, clean, and free of dust and contaminants. Wood subfloors must be primed with an acrylic primer prior to Apex Multi underlayment application.
Note: This underlayment is not a structural material and will not resist building movement. Any structural movement in the building can cause stress that may result in cracking of the underlayment.
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