Can I Put a New Subfloor Over an Old Subfloor?

Introduction to Subfloor Installation

Installing a new subfloor over an old one is a common and practical solution in home renovations. This guide will explore the feasibility, steps, and considerations for such projects, providing valuable insights for DIY enthusiasts and professional renovators alike.

Prerequisites for Installing a New Subfloor

Before tackling the project, ensure the existing subfloor is stable and free from significant damage. A subfloor that is in good condition can support a new layer of plywood effectively.

Preparation Steps

1. Clean and Level the Old Subfloor: Thorough cleaning and ensuring the old subfloor is level is crucial. This prevents any unevenness in the newly installed subfloor. 2. Inspect the Nails and Screws: Check if the old nails or screws are reliable. If they are loose or popping out, secure them with new fasteners. 3. Use Secure Fasteners: To prevent squeaks and ensure stability over time, use screws rather than nails to attach the new plywood.

Benefits of Installing a New Subfloor Over an Old One

Adding a new subfloor can strengthen the floor and create a smoother surface for finishing work. For instance, plywood laid over an uneven subfloor can help smooth out the surface, making it easier to install hardwood or laminate flooring.

Case Studies

1. Example with Hardwood Flooring: A DIYer planned to install tg hard maple and cork flooring. The original subfloor was solid but had irregularities. To improve the surface, the old subfloor was refastened using screws and 5/16" plywood was installed with power-driven staples. This method ensured a quiet and secure installation. 2. Kitchen Remodeling: During a kitchen renovation, the old 3/4" thick 1x4 Douglas Fir flooring was removed due to its poor condition. New plywood was installed to match the original floor thickness of 1/2". This approach ensured seamless transitions and a smooth installation process. 3. DIY Subfloor Installation: Currently, a homeowner is putting 1/2" plywood over the original subfloor for a new laminated flooring project. This approach ensures the new flooring matches the original thickness and provides a stable base for laminate installation.

Challenges and Solutions

While installing a new subfloor over an old one is feasible, there are challenges that need to be addressed, particularly with door and threshold heights. Removal and reinstallation of doors, trim, and bathroom fixtures may be necessary to maintain proper levelness and safety.

Example Solutions

1. Removal and Reinstallation of Fixtures: To accommodate different heights, fixtures, and thresholds, these elements may need to be removed, adjusted, and reinstalled. For instance, if the new subfloor raises the floor level, you may need to trim doors and thresholds to ensure they fit and operate smoothly. 2. Ensuring Secure Fasteners: Cleaning the subfloor, vacuuming, and securing it with subfloor screws is essential. Adding a layer of pL400 (a moisture-resistant underlayment) and another layer of plywood can further enhance the stability and moisture resistance of the new subfloor.

Conclusion

Installing a new subfloor over an old one can be a practical and effective solution, provided that you follow the necessary preparatory steps and address potential challenges. Whether you are a professional or a DIY enthusiast, understanding these aspects will help you achieve a successful renovation project.