Tools & Materials
Which Tile Backer is Best?
In this article we’ll explain the pros and cons of various tile substrate products, so it will be easy to decide which tile backer to pick for your next project.
In this slideshow, we’ll explain the pros and cons of various tile substrate products, so the next time you visit your local home center or tile shop, you’ll have a better understanding of which products to pick for your project.
This is the traditional tile backer. Felt paper is stapled to the floor and covered with expanded metal lath. Then cement, sand and water are mixed together to a crumbly consistency and floated over the lath to form a flat surface. Given the complexity, it’s easy to see why even experienced tile setters use backer board when they can.
But a mortar bed does have advantages. There’s no cutting or fitting of boards. And a mortar bed is good for leveling and flattening uneven or out-of-level floors, which are common in old houses. If you’re handy with a trowel and understand how to set up and use screeds as a guide for leveling or forming the mortar, pouring a traditional mortar bed may be a good alternative to tile backer board, especially on uneven or sloping floors. An 80-lb. bag ($8) will cover about 10 sq. ft.
If you have floors that are wavy or out of level, self-leveling underlayment is a great solution. It has many of the same advantages as a dry-pack mortar bed but doesn’t require as much skill to install. You still use metal lath, but then mix bags of powder and pour the soupy mix onto the floor. It’s also fast.
But there are downsides. Using self-leveling underlayment takes careful prep work. You have to seal every little hole in the floor so the underlayment doesn’t seep into spaces below. And most formulas harden very fast, so you have to plan carefully to mix and pour quickly. Self-leveling underlayment is also expensive. At home centers, a bag of self-leveling underlayment costs about $32. For more on how to use self-leveling underlayment, check out our story here.
Cement board is the most common and well-known backer board. It’s readily available and relatively inexpensive (about $10 for a 3 x 5-ft. sheet). The 30-in. x 5-ft. and 3 x 5-ft. sheets are sized for efficient use around bathtubs and showers. The core isn’t waterproof, but it can withstand getting wet without falling apart, so even if your waterproofing system leaks, the board will stay intact. On the downside, the boards are heavy, somewhat difficult to cut and can leave abrasive sandy crumbs that can damage tubs and shower bases if you’re not careful.
Cement board is a good, reliable backer board that works well on both floors and walls. But most tile setters err on the side of caution and brush on a waterproofing membrane when the cement board is in wet areas like showers or tub surrounds.
Fiber cement board
Fiber cement board (HardieBacker is one brand) is a variation of cement board that’s made from compressed cement and sand, reinforced with wood fibers throughout. Like cement board, the boards are heavy and hard to cut. And it’s even more brittle than cement board, so you have to be extra careful to keep screws at least an inch from the edge to avoid breaking the board. Fiber cement board is available in 1/4-in. and 1/2-in. thicknesses. The 1/4-in.-thick board is typically used on floors and countertops. A 3 x 5-ft. sheet costs about $12. Since fiber cement board is similar to regular cement board, it makes sense to choose the one that’s cheaper or more readily available.
Foam-core tile backing board has two big advantages over other backer boards. First, it’s super lightweight compared with the rest. A 1/2-in.-thick, 3 x 5-ft. sheet weighs just 7-1/2 lbs. compared with 45 lbs. for a similar size sheet of cement board. And second, since it’s foam, the board is super easy to cut with just a utility knife. Another advantage is that the polyisocyanurate foam core is waterproof. You don’t have to rely on a surface membrane or worry about the board failing if the core is exposed to water. However, you do still have to take care to waterproof the seams and the fastener penetrations to create a waterproof assembly.
The main drawback to foam-core board is the high cost (about $22 per sheet), twice that of other backer board. But considering the light weight, ease of installation and waterproof core, this backer board is a perfect fit for most DIY applications. GoBoard and Kerdi-Board are two common brands of foam-core backer board.
Glass mat gypsum
Water-resistant gypsum board, or “green board,” was used in the past as a tile backer but is no longer recommended, mainly because better products are available. Glass mat gypsum board is a better choice. The sheets are made from water-resistant silicone-treated gypsum, reinforced on both sides by fiberglass mats. DensShield is one common brand. It’s easier to cut than cement board, and it’s mold resistant and has a built-in moisture barrier. Dean, our tile consultant, says glass mat backer board is his first choice for ease of installation and cost and because his helpers like it. DensShield costs about $10 for a 2.7 x 5-ft. sheet.
If you’re looking for a way to minimize height buildup and eliminate a large level difference at thresholds, a mat product is a good solution. Ditra is a 1/8-in.-thick polyethylene membrane with a layer of anchoring fleece on the underside and a grid of square cavities on top. Installation is simple. You trowel a layer of thin-set adhesive on the floor and embed the mat in it. Then you fill the cavities with thin-set to create a strong, waterproof tile backer that also functions as an uncoupling membrane. The completed assembly takes the place of more traditional backer board when installed over 3/4-in. wood subfloors. A 3 x 3 x 16.4-ft. roll costs about $110. SpiderWeb II uncoupling mat is a similar product.
Shower floors have always been one of the trickiest tile bases to install because they have to slope toward the drain and be completely waterproof. Traditionally, a waterproof membrane was placed under a sloping mortar bed, a process that required a lot of skill and experience. But thanks to new products, installing a shower floor is a job DIYers can tackle.
Schluter makes a system that includes a preformed foam floor, drain, curbs and waterproof membrane. Starting at about $500, it’s expensive, but it allows you to create a perfect, waterproof shower floor without having to pour a sloping mortar bed. Or for a similar price, you can buy a rigid plastic shower base with a surface that’s designed to tile over. Finally, if you would prefer to pour a traditional dry-pack mortar bed, Mark E Industries sells a Quick-Pitch Kit (photo right; starting at about $40), which contains tapered plastic shims that act as screeds, allowing you to easily get just the right slope on the floor.
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