Can You Pour Cement Mix on Plywood Floors? 

Yes, you can pour cement mix onto plywood, but success hinges on critical cement mix choices and substrate prep. Using the wrong cement mix or technique risks cracks, delamination, and structural failure. This guide reveals how to leverage cement mix for durable plywood-based floors.

Why Cement Mix Selection is Non-Negotiable

Not all cement mixes work on plywood. Key factors:

• Water-Cement Ratio: High water weakens the mix and swells plywood. Use low-slump mixes (≤4") or additives like superplasticizers.

• Reinforcement: Fiber-reinforced cement mix (polypropylene/steel fibers) resists shrinkage cracks on flexible wood surfaces.

• Type of Cement Mix:

  • Standard Portland Cement Mix: Requires strict water control.

  • Polymer-Modified Mix: Bonds better to plywood (e.g., SBR latex additives).

  • Self-Leveling Cement Mix: Ideal for thin overlays but needs primer/sealed plywood.

Pro Tip: Use 3,000–4,000 psi cement mix for optimal strength-to-weight balance on plywood.

Step-by-Step: Pouring Cement Mix on Plywood

1. Plywood Prep (The Foundation)

• Seal the Wood: Apply 2 coats of polyurethane sealer or use film-faced plywood.

• Bonding Agent: Brush a cement slurry (1:1 cement mix + bonding adhesive) onto plywood 10 mins before pouring.

2. Mixing & Pouring Cement Mix

• Mix Design:

  • 1 part cement : 2 parts sand : 3 parts aggregate (<10mm)

  • Add 0.5% fibers by volume for crack resistance.

• Pouring:

  • Layer thickness: ≥2 inches (thinner layers crack easily).

  • Work in sections ≤100 sq ft to control curing.

3. Curing for Maximum Strength

• Cover with plastic sheeting for 7 days (prevents rapid moisture loss into plywood).

• Avoid foot traffic for 72 hours.

Critical Mistakes to Avoid

•  Using high-water cement mix → plywood warps and bonds fail.

•  Skipping fiber reinforcement → shrinkage cracks within 24h.

•  Pouring on unsealed/unsupported plywood → deflection causes cracks.

When to Avoid Cement Mix on Plywood

• Subfloors with >1/8" deflection under load.

• High-moisture areas (bathrooms) unless using waterproof cement mix + membrane.