Over the years, we have fielded literally thousands of questions regarding tiles and tile products. NHD has put together a collection of some of the most frequently asked questions about porcelain and ceramic tiles, various types of grout, in-floor heating systems as well as Schluter Systems Products and more.

  1. What are rectified tiles?

When a tile is "rectified" its edges are cut at the factory after it is baked. The natural, pressed and somewhat rounded edges of the tile are cut and machined to produce a fairly sharp, precise edge with a micro-bevel and a flat surface at the perimeter. This procedure is common for porcelain floor tile but is also sometimes performed on large format ceramic wall tiles. With this precision the tiles can be set with a 2 mm to 3 mm grout joint and due to the flatness at the edges the joints are less visible.

  1. Can a wall tile be used on a floor?

No. Wall tiles have a weaker glaze and body and will wear prematurely. It is also not as resistant to impact and stress when used as a floor finish and may spall, chip and crack. However, a floor tile can definitely be used on walls.

  1. What is the difference between a porcelain floor tile and a ceramic floor tile?

Today, most floor tiles on the market are porcelain. A porcelain tile is essentially a ceramic tile in the architectural world, that is, there are two classifications of ceramic tiles, porcelain and non-porcelain. The latest styles and designs are only manufactured as porcelain products. Porcelain floor tiles have a denser body and, typically, harder glazes than ceramic floor tiles. In its manufacture, higher temperatures and finer clays are used and an extra mineral component is added to make it a porcelain tile.

  1. What is a "glazed and polished porcelain tile"?

This is a highly polished porcelain tile, usually rectified, that is produced by applying a thick glaze, machining it smooth and polishing it. Glazes are necessary for printing broad digital inkjet designs onto the tile. Unglazed porcelain, which can also be highly polished, is not suitable for most digital inkjet designs.

  1. What is a "lappato or semi-polished porcelain tile"?

The finish on different semi-polished tiles can vary from a very slight polish on the high spots of a textured glaze to an almost fully polished surface that reveals some pits or dull areas. Often it is done to more authentically duplicate stone tile which have some natural fissures. It is also less slippery and less susceptible to visible scratches than fully polished tiles.

  1. What is an "unglazed and polished porcelain tile"?

Unglazed porcelain tiles are highly polished and have rectified edges. They are usually through-body porcelain and suitable for commercial traffic. Some of them are treated with an impregnating sealer at the factory whereas others may have a label on the carton that states that a solvent-based impregnator needs to be applied during installation.

  1. What does "digital technology" mean?

This term refers to the tile's design that is printed onto the surface. "High Definition" is another industry marketing term to describe the process. Today, images that are created from photographs by a computer program are then applied to the tile by inkjets, much like modern office printers. With this technology the designs are more exciting and attractive than ever.

  1. What size grout joint should I use?

The tile type often dictates what size joint space to use. It is desirable to have small joints in most cases. If a tile is rectified a 2 mm or 3 mm space is possible. For many floor tiles a 3 mm, 4 mm or 5 mm joint is good. It often depends on the calibration of the tiles. Unless a tile has been rectified, most tiles are not 100% perfectly sized from one to the next, therefore a bigger joint than 2 mm is required to enable a proper installation. They can sometimes vary in size from tile to tile by a half millimetre or 1/64" or so due to baking and drying factors during production, which is normal.

  1. What is a shade variation scale?

Some manufacturers use the V scale for grading the shade or tone variations of a particular tile product from piece to piece. The tone variations are intentional and part of the design. Many porcelain floor tiles that emulate natural stone benefit from changes in tone from tile to tile and more closely resemble the real thing. Substantial variation (V4) can also be quite attractive for certain tile designs.
V1 = little or no shade variation
V2 = slight variation
V3 = moderate variation
V4 = substantial variation

  1. Should I use sanded or non-sanded grout?

The rule used to be to use non-sanded grout for joints 1/8" or less and to use sanded grout for joints bigger than 1/8". However, today there are universal grouts available that are produced with finer sand particles and will work for most joints. These "New Generation" grouts are so fine that they can be used with glass mosaics, wall tiles and many polished stone tiles without scratching the surfaces.

  1. Is tile too slippery for exterior walkways?

Some tiles are suitable and safe for exterior entries, stairs, pool decks, etc. It depends on the texture of the tile. There is a German slip resistance classification (DIN 51130) which uses "R-ratings" that is most commonly used by residential designers. For exterior residential walkways an R10 tile or greater is recommended. There are porcelain tiles available that have R11, R12 and R13 ratings for even more safety.

  1. What is lippage?

The term "lippage" is an industry-exclusive word for unacceptable height differences between adjacent tiles. Tiles should be set so that the edges are flush with each other. Not only is lippage unacceptable aesthetically but on floors the tiles will be prone to more abrasion at the protruding edges.

  1. What is epoxy grout?

Epoxy grout is a specialty joint filler made mostly of sand, dyes, epoxy resin and an epoxy catalyst. These components are mixed together at the time of installation. The mixing, grouting and washing techniques are a bit different than cement grout applications and require some proficiency. The result is a very tough, color-fast, waterproof and stain-proof grout.

  1. What is "New Generation" grout and mortar?

These are hi-tech European installation mortars and grouts that have light-weight and anti-slump qualities among other advantages over typical products.

  1. What is the best way to cut tiles?

Almost all ceramic and porcelain tiles can be straight cut very precisely and quickly with a manual tile cutter that scores the surface and then splits it. A wet-saw or handheld grinder can be used to do L-shaped cuts and such. Many glass tiles and mosaics can also be cut with a manual score-and-snap tile cutter. Stone tiles need to be cut with a wet-saw or high speed grinder. Ceramic wall tiles are the easiest to cut and drill into. Today's dense porcelain tiles require more expensive blades and bits to efficiently cut and drill them. Visible cuts in an installation benefit from being sanded with a wet diamond hand pad to soften and smooth the edge.

  1. Should I apply silicone caulking at inside corners?

Since inside corners often experience movement that can crack grout, it is recommended to caulk them with 100% silicone sealant. Today there are color-matched silicone sealants available in the same colors as grout. A kitchen backsplash, for instance, requires silicone sealant at the countertop to wall junction to seal it against water and eliminate the problem of cracked grout due to inevitable movement. Showers and bathrooms are also enhanced when the inside corners are caulked properly with silicone. Please note that 100% silicone sealant is superior to acrylic, latex or "siliconized" caulk that is on the market. It is the correct product to use.

  1. Can electric in-floor heat systems warm the entire room?

Yes. These electric cable or mat systems generate over 40 BTU's per square foot which is more than a typical baseboard heater. Not only that, but an in-floor heat source is the most comfortable and pleasant form of heat.

  1. Can you tile over old tiles?

Yes. If the substrate is stable and the existing tiles are without failures it can be a very practical solution. Please note that this method is intended for dry, interior areas only. There is an adhesion promoting primer available, which is excellent for preparing walls or floors for this purpose.

  1. Do you have to seal grout?

No, although traditional cement grouts will certainly benefit from an application of a natural-look impregnator but it is not a necessity. "New Generation" cement grout doesn't need it at all; it is dense enough to resist staining.

  1. Do you have to seal stone tiles?

Yes, it is recommended to seal most stone tiles.

  1. What is impregnator?

Impregnator is a non-film-forming sealer that penetrates stone tiles and grout but does not leave a finish on the surface. It is very effective against oil and water based stains. It's available in natural-look, which doesn't change the appearance of the stone after it is sealed, and in a color enhancing version. Impregnator is easy to apply and long lasting.

  1. Can I use acid to clean tiles?

It is not recommended to use products such as muriatic acid to clean glazed tiles and grout. It can damage the grout and the tiles. In some cases, such as when a stubborn grout haze is left on the tile, an "acid cleaner" especially made for tiles is okay to use if the directions are followed carefully.

  1. What is the best way to maintain tiles?

Simply dry sweeping is good for floors to prevent soiling. Occasionally a good cleaning with pH-neutral tile and stone cleaner is recommended for floors and walls.