Let’s get straight to the point: luan (the plywood-based product) should only be used as a subfloor for tiles if you love tiling and can’t wait to redo your entire project again soon! Although it is often used as an underlayment when putting down material such as vinyl sheets, it is not suitable for use under tiling. Here’s why:
Luan is unsuitable as a subfloor for tile because it is too thin to meet tile industry standards. Equally, luan is a plywood material that contains ingredients that adversely affect the effectiveness of thinset or adhesives. Its low compressive strength means that it can dip in high traffic areas.
If you already have an existing luan underlayment that was set under a different surface, you may be wondering if you can use it for tiles. Let’s find out more about this material so you can make an informed decision.
What Is Luan?
Luan, or lauan as it is sometimes called, is a plywood product made from tropical trees. The name luan comes from a specific type of tree that grows in some Southeast Asian countries, including the Philippines.
A soft plywood material is made by gluing together various layers of red or white luan, sometimes known as Philippine mahogany or meranti. The resulting plywood panels are usually ¼ inch or 1/8 thick.
Because the end product is made from thin strips of veneer that have been glued and pressed together, the surface appears smooth and perfect. However, this is where many tilers become unstuck. One should never just a book by its cover, and in this case, luan must not be regarded as a proper plywood subfloor even if it looks like one from the outside.
Luan is a great product. It is light and easy to cut. This makes it ideal for small crafts and toymakers. In particular, it is the perfect thing to use if you are making a dollhouse or theatre sets. It is absolutely not the right thing to put below a bed of tile.
Why Is Luan Unsuitable To Use Under Tiles?
Just because luan looks like a perfect plywood subfloor for your project, there are multiple reasons why a tiling project over this material is a really bad idea. Let’s go through the main ones:
- The additives in luan plywood will affect the cure of any adhesives like thinset or mastic laid over it.
- It contains resins and chemicals that can leach out and stain grout between tiles over time.
- It is too thin to use as a subfloor. The thickest luan is only ¼ inch thick.
- Luan is not made to hold weight. It compresses easily and inconsistently. Soft parts may get squashed flat in one spot and be fine in another.
- Luan is made of thin, soft layers, so when it gets wet, the layers can start dissolving. Plywood used for subfloor purposes should be thick exterior grade plywood topped with cement backer board. Luan is not suitable.
- Luan is not made with approved exterior quality adhesive, so the moment it gets wet, it will start delaminating. Grout is seldom entirely waterproof, so sooner or later, water may get through, and the luan will quickly rot or swell. Neither will be good for your tiled surface.
- Luan is not an approved substrate for any thinset. It buckles easily and may crumble on contact with the thinset.
Should You Remove Existing Luan Before Tiling?
There is no workaround if you have a layer of existing luan if you are dead set on tiling. Sure, some people might have been lucky and had luan under their tiles for years without issues, but the chances of something going wrong is simply too high to take the chance if you are laying new tiles.
Each time you move a heavy appliance or drop a mug of coffee on your tiled floor, the last thing you need to be thinking about is whether your subfloor may buckle. It is undoubtedly worth the extra work and expense of ripping out whatever luan you already have installed and starting with something you know will last.
According to the University Of Massachusetts article about underlayments for resilient flooring, although luan is a popular choice for builders when laying thin, flexible surfaces like vinyl, it is not always a great choice even then. They include a warning that no manufacturing specifications support its use even as an underlayment.
Besides the moisture problem, luan doesn’t handle compression well, and if you have a weighty object placed on it, the surface may start to dip slightly. While this is not as terrible if it is topped with a resilient floor surface like linoleum, vinyl, or cork, any dip or compressed spots below a tiled surface will almost certainly result in unsightly surface cracks.
Besides the compression issue, luan is made using adhesive ingredients and may also contain various wood oils. There are two types of luan:
- Type 1 – made with exterior glue.
- Type 2 – made with water-resistant glue.
The type of plywood board is stamped on the edge of each panel.
There is no luan in existence that doesn’t contain some type of additives. That may not seem like an issue, but the moment you add a layer of thinset or mastic, the substances holding the layers of luan together get wet, which is not ideal for the layers of luan veneer. Your adhesive will not be able to effectively adhere tiles to the damp layer of soft spongy wood.
The American Plywood Association (APA) does not provide any assurance about compliance in products that contain luan. The Tile Council of North America has set specific approved plywood standards which they deem suitable to receive tiled surfaces, and of course, those standards must be APA approved. Therefore, popping a layer of tiles over a luan surface will quickly cancel out any warranties.
You may read that luan can be used as an underlayment – but remember that it is not the same as a subfloor for tile. In fact, luan isn’t even a good underlayment material, but it is easy to work with and cheap, so if you plan to roll out a couple of sheets of vinyl and it doesn’t have to last forever, it’s not an altogether bad choice.
However, for tiles, it’s not suitable. If it’s already in, it’s a good idea to rip it out and use something durable.
Can You Put Peel & Stick Tile On Luan?
Luan plywood is made by gluing thin layers of light, tropical wood together to form a flexible, easy to work with surface. Putting peel and stick tile on luan is not recommended because it contains oil resin that will prevent proper adhesion of your tiles.
If you go ahead and stick your peel and stick tiles onto the luan surface, it may look great at first, but as the oils leach out of the plywood surface, the sections of tile will slowly start lifting from the wall. Worse still, it won’t be easy to run a film of mastic behind the lifting area and glue it back down. Luan doesn’t do well being added to other adhesives, and it can affect the properties of the glue.
The success of a peel and stick tile application depends on its ability to stick and remain adhered to the surface that it is applied to. Sticking it onto a potentially oily layer of luan is not a good idea. Using peel and stick tiles over luan is also likely to void any manufacturer warranties.
Endnote About Luan and Tile
When it comes to using luan as a subfloor for tile, there is no middle ground. Although it is light, inexpensive, and easy to work with, it should never be considered as a subfloor for tiles. It is just a bad idea because it is too soft and thin, and it will begin to disintegrate the moment any moisture gets into it.
If you still need some convincing, check this rather amusing thread on the Popular Contractor Talk forum. It seems that the only time that luan comes out on top of a list when tile is concerned is on the materials NOT to use!