Prepare a Subfloor for Hardwood
Installing hardwood floors has many advantages: it has a pleasant appearance, an impressive durability, and adds value to your home. After removing your old flooring, you will be left with a plywood or concrete subfloor. Prepping the subfloor correctly is essential before installing the hardwood. A properly prepared subfloor will be clean, dry, level, and structurally sound - all characteristics that will help ensure a lasting, worry-free floor installation. Follow the steps below to learn how to prepare a subfloor for hardwood.
Steps
- Clean the subfloor as necessary. Before installing the hardwood flooring, the subfloor must be as clean as possible. Spilled paint, adhesives, or other coatings, as well as dust and debris, can mar the flooring installation if not cleaned away.
- If you will glue your hardwood flooring down, the subfloor must be completely clean. Any coatings of paint or adhesive should be sanded away with an electric sander. Extra care should be taken to vacuum away dust created from the sanding.
- If you will be installing nail-down, floating, or locking hardwood, you do not need to sand away spills and coatings. Simply use a vacuum to remove all dust and dirt.
- Ensure that the subfloor is as level as possible. A level subfloor will ensure that your hardwoods fit together neatly and do not creak or sag.
- Use a long spirit level to check the levelness of the subfloor in multiple areas and in multiple directions. A good guideline is that only 3/16 inch (4.7 mm) of height variation is permissible per 10 feet (3 m) of floor length.
- High spots can be sanded down with an electric sander. For especially difficult or large areas, a special floor sander will be more suited to the task.
- Low spots should be filled in with cementitious leveling compound. However, this compound is not appropriate for nail-down applications, as the nails can cause the compound to crack and crumble. Consult the flooring manufacturer's directions for filling low spots in this case.
- Check the moisture level of the subfloor. Excess moisture in the subfloor can cause hardwood floors to warp, while excessively dry subfloors can lead to cracked, creaky floors. You should assess the moisture level of the subfloor before installing the hardwood.
- This process is best done with a moisture test kit, which can be purchased in the flooring section of a home improvement store. These kits usually consist of a test strip that you place on the floor and cover with a plastic enclosure. The test strip will change color depending on the subfloor's moisture content.
- If the subfloor's moisture content is not within the acceptable range, consult the flooring manufacturer's instructions for possible solutions. The safest route in this case is to install a different type of flooring with a higher tolerance for moisture levels.
- Assess the subfloor's structural integrity. The subfloor's job is to spread the load of everything in the room (including the flooring, furnishings, and people) evenly across the floor joists. It should be structurally sound before the hardwood flooring is installed.
- Check to make sure none of the plywood sheets are loose or squeaky. If they are, screw them into the floor joists until they are firmly secured.
- Determine the thickness of the plywood subfloor. A thicker subfloor will be more stable; your flooring manufacturer will have recommendations for subfloor thickness. Typically, plywood subfloors should be 3/4 inch (2 cm) or thicker. You can check this thickness easily by drilling a small hole through the subfloor.
- Proceed with the flooring installation. Once your subfloor is clean, dry, level, and structurally stable, you can install the hardwood floors. Make sure to install a moisture barrier underneath the flooring if specified by the manufacturer.
Tips
- You will likely need to remove your baseboards in order to install the flooring with the proper clearance for expansion gaps.
- Before installing the hardwood, allow it to sit in the room for at least 72 hours. This will acclimate the flooring to the moisture level and temperature of the room, which will reduce problems involving expansion and contraction.
Things You'll Need
- Sander
- Vacuum
- Spirit level
- Tape measure
- Leveling compound
- Moisture test kit
- Drill
- Screws
