Laying Tile Over a Plywood Subfloor
When I started my career in the home improvement sector, laying a tile floor was a heavy and messy business, but fortunately, today it is a lot much simpler and straightforward. New materials and techniques now allow for the do-it-yourself home improvement enthusiast to get their hands dirty, while saving a lot of money in terms of labor.
More than that, there is always the sense of satisfaction that goes with doing a job well in your own home.
The old method for laying tile over a wooden subfloor (usually plywood but not always) was to lay down a bed of mortar as prep for laying the tile. Today, hardibacker or cement board cuts this job out and lends itself to handling and working by anyone with the ability to lift a ½ inch thick, 3×5 sheet. Cement board is simple to measure and cut, even when you have odd angles or fittings to get around (such as pipes) and it is good for almost any situation.
Here are a few tips on what to do which you are not likely to find in the manufacturers guidance notes and which are gleaned from experience.
Always remove the old flooring covering because this will allow you to get a good look at the condition of the subfloor. Years of water seeping through cracked grouting or sealant will create damp conditions and lead to rot – if you don’t look and check, you are not going to know you have a problem until your new floor starts cracking! Repairing the subfloor is usually as simple as cutting out old wood and refitting with ply – a simple and inexpensive repair which can save your entire installation.
I always set new screws into the subfloor to ensure it is firmly fixed to the underlying joists. Again, a simple and cheap task which can be done in a few minutes but by ensuring you have a firm subfloor, you will avoid movement which will lead to your new tile cracking or lifting. Make sure you sink the screw heads into the ply so they do not “sit up” above the level of the subfloor and make sure you use corrosion resistant screws (never use drywall screws for this job).
Use a leveling compound (lightweight gypsum) to make sure you have no voids or gaps, and this is also useful for any low spots you have in the subfloor. Take extra care if you don’t have a level subfloor, as sometimes it’s better to simply take it up and use shims to get a level surface rather than apply layers of leveling compound.
You’re now ready to start laying tile, or at least you are once you’ve cleaned the area so it is free of dust and unwanted objects such as loose screws. You can lay a tile floor over an existing one, but I don’t recommend this – the subfloor and old tile must be in excellent condition and you have to scuff up the old tile so the tile adhesive can stick to it. Best to remove the old tile and lay cement board as above and make sure you have the proper foundation.