New flooring hinges on condition of subfloor

Hey there, time traveller!
This article was published 06/01/2002 (8874 days ago), so information in it may no longer be current.

QUESTION:

Since considering changing our flooring we’re facing numerous questions. We have vinyl tiles installed on 3/8-inch-thick particleboard in the kitchen and washroom, and carpet everywhere else. The subfloor is 3/4-inch OSB nailed in 2×8 joists. Our 15-year-old house did not seem to shift, at all, in the 10 years we’ve been here.

We would like to change from vinyl to ceramic tiles and replace the carpet with 3/4-inch solid, 2-inch-wide pre-finished hardwood strip flooring. We did some reading on this subject, narrowed down the material and colour selection, reviewed recommend installation methods and obtained quotes and details for the work.

For the hardwood floor: Is nailing the h/w directly into OSB accepted practice? Are there any potential problems with this? If plywood is required, how many layers and in what thickness? Should it be screwed, nailed, glued?

Secondly, should the vinyl tiles be removed before installing the metal mesh & mortar base for the ceramic tile? Should a layer of plywood be installed first? What is the best, most cost-effective way to proceed for both new floor coverings?

— Rasvan Dragne

ANSWER:

The reason there have been many opinions on the proper method of floor preparation, is that many different approaches will give a satisfactory result. The choice will depend largely on the condition of the existing subfloor and floor coverings.

The first thing the homeowner should look at is the condition of the vinyl tile floor covering and carpeted areas. Are there any areas of extreme wear or very high-traffic areas? Are any of the floors noisy or squeaky when walked on? Are the floors bouncy or do they have large amounts of deflection when jumped on? Do objects on the floor shake or rattle when someone walks by?

In an ideal situation, the new carpeting could be put over the existing subfloor, and the mortar bed and ceramic tile could be installed directly over the vinyl tile. But this is rarely the case, especially if the original OSB sheathing has been nailed. There probably are areas that are noisy due to loosening of nails and shrinkage of materials. The existing subfloor should be secured and often another layer of sheathing added before installation of new coverings.

For the carpeted areas, screwing down the existing sheathing, after removal of the old carpets, may be sufficient to hold the new hardwood. The proper flooring screws should be used along with a screw-gun or drill and adapter to refasten the subfloor to all the joists. Loose nails may be hammered down or removed after the entire floor is newly fastened. The need for any additional layers of plywood will depend on the condition of the old floor, the hardwood installer’s preference, and the finished height of the new flooring in relation to the ceramic tile floor.

Ceramic floor tiles and the mortar bed beneath will add significant thickness to the existing floor, and may leave a bump up to the kitchen and bathroom. It is for this reason the existing particleboard and tile floor may be removed, if desired. It is often easier to tear up an entire subfloor of particleboard than to remove the vinyl on top. This is only practical if this sheathing was not glued to the original subfloor, which would make removal much more difficult.

If height difference is not an issue, the metal lath and mortar bed may be installed directly over the old flooring, if it is not loose or uneven. In this case, longer screws should be used to fasten through all the layers of sheathing to secure them to the floor joists, before installing the mesh.

The metal lath normally will be stapled down to the material beneath, and will provide an even and sturdy base for the ceramic tile. This will help with adhesion of the tiles and prevent cracking due to shifting.

The most cost-effective way of doing the job often is not the best, but may be sufficient in many cases. The ideal situation is to remove all the sheathing and floor covering down to the original OSB, then screw it tight and add additional layers of sheathing to provide a smooth and even transition from the hardwood to the tile.

This likely will be the most expensive method. Consultation with installers beforehand will provide the best advice.

The most important thing is to secure any floor sheathing as well as possible, with proper screws, before the new flooring is installed. This is the ideal time to get rid of old squeaks, as it will be very difficult afterward.

Ari Marantz is owner/inspector of Trained Eye Home Inspection and is PR rep for the Canadian Association of Home Inspectors — Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, PO Box 69021, Unit 110, 2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at 291-5358.