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Frequently Asked Questions and their answers. If you have any additional questions please call or visit our showroom 

What’s the Difference between Porcelain Ceramic Tile and Non-Porcelain Ceramic Tile?

First things first: the word “ceramic” is an umbrella term for any “earthen-ware” product that is fired (baked) in a kiln. Porcelain tile is a type of ceramic. “Red Body” glazed floor tile is a type of ceramic. Terracotta flower pots are a type of ceramic. China dishes are a type of ceramic. With this understanding, let’s review the most important differences between Porcelain Ceramic Tile and Non-Porcelain Ceramic Tile. 

Porcelain Floor Tile is vitreous; this means it has very low water absorption, less than .5% - almost “glass-like” in its molecular structure. It is fundamentally non-absorbent. Porcelain tile is composed of 3 basic ingredients; kaolin (high quality clay) acts as the binding agent, feldspar (mineral) provides vitreosity and quartz (sand) reduces shrinkage in the firing process. Porcelain tile is more dense, durable and harder than non-porcelain floor tile.  It is ideal for heavy traffic areas of the home - for example; kitchens, entries and walking patterns. And, it is the best choice for all commercial applications. It is frost resistant and can be used in exterior applications. Because of its density and hardness, it has higher impact resistance than most non-porcelain tiles.  Commercial and institutional settings are best suited to porcelain tile floors because of its strength and stability. 

Non-Porcelain Ceramic Floor Tile is composed of clay, sand and water. This type of ceramic tile does not include the added minerals that are in porcelain tile. Often the raw clay is not highly refined. Organic content in this type of clay burns off during the firing process and leaves vacancies in the body of the tile making it sponge-like in its structure. Due to this characteristic, the water absorption rate of non-porcelain tiles is greater the 0.5%, in other words, this type of tile is often highly absorbent. A quick way to determine if tile is porcelain or non-porcelain: pour a little water on the back of the tile. If water soaks into the back of the tile, it’s not porcelain.  This type of floor tile is not as dense and durable and is more prone to chipping in high traffic areas. While many of the most beautiful hand-made floor tiles are not porcelain, they can be used successfully on floors when installed properly and in appropriate settings. They are better suited for light duty floors like bedrooms, bathrooms and other floors that are not exposed to heavy use and foot traffic. Use common sense and follow manufacturers guidelines.

What is Through-Body and Color-Body Porcelain Tile?

Through-Body is a term for porcelain tile that has pigment mixed throughout the body of the tile. The color on the surface of the tile is homogenous throughout the tile; from the top to the underside. It is also referred to as “Un-Glazed Porcelain Tile”, as it does not have a glazed surface.  It is extremely durable, has a very high abrasion resistance and is the best type of porcelain to be used in airports, shopping malls, hospitals and other heavy commercial sites. For most homes, this type of porcelain tile is an overkill and often has a commercial or institutional look that doesn’t suit residential settings.
Color-Body is porcelain tile that has pigments mixed throughout the body to coordinate with the colors of the glazed surface of the tile. The glazed surface is the part of the tile that provides its decoration, look and style. If the glazed surface is chipped, the “color body” matches the overall color of the surface; thereby making a chip less noticeable.

What is the PEI rating for floor tiles ?

The term P.E.I. rating is associated with the Porcelain Enamel Institute and not the tile industry. The appropriate term is Visible Abrasion Classification. As stated in ASTM C1027-19, it is the “Standard Test Method for Determining Visible Abrasion Resistance of Glazed Ceramic Tile”…
…“The abrasion resistance of tile surfaces is determined by rotation of an abrasive load on the surface and the assessment of the resultant wear by means of visual comparison of the abraded test specimens and non-abraded tiles. A staining agent in light oil may be used to help determine whether abrasion surface is likely to result in mechanical entrapment of dirt particles.”
Tile manufacturers submit samples of tiles to the Porcelain Enamel Institute for testing. The results are typically published in product catalogs and brochures.

PEI Class 0. - WALLS ONLY; Not recommended for floor application.
PEI Class 1. - LIGHT DUTY RESIDENTIAL FLOORS; Rooms receiving bare feet and light foot wear
PEI Class 2. - RESIDENTIAL FLOORS - Residential light duty floors
PEI Class 3. - HEAVY RESIDENTIAL / LIGHT COMMERCIAL – All residential and light commercial floors
PEI Class 4. - COMMERCIAL – All residential and medium duty commercial floors
PEI Class 5. - HEAVY COMMERCIAL; All residential and heavy commercial floors

What is rectified tile?

Tiles, like other earthen-ware products that are fired in a kiln, will vary in size from one production run to the next and also vary slightly within a production run. This is a characteristic (not a flaw) of tile and other fired ceramic products. The variation is due mostly to environmental factors; fluctuations in kiln temperature, humidity level, weather & barometric pressure, operator differences, etc.


These small variations dictate grout joint width. The more variation in size, the larger the grout joint needs to be. If each tile is exactly the same size, a very small grout joint can be used.
To “rectify” this characteristic, the perimeter edges of tiles can be cut (machined) to produce tiles that are all exactly the same size & dimension. Rectified tiles can be set with the smallest grout joint width because every tile is exactly the same dimension.

This is an added step in the manufacturing process that increases cost. Generally, you can expect rectified tiles to cost more than “factory-edge” un-rectified tiles.

Can you tile on top of other tiled surfaces; floors and shower walls?

The Tile Council of North America allows “tile-over-tile” floor & wall installations as described in the TCNA Handbook Detail TR712 and TR713. An on-site inspection is necessary to determine if this method is suitable. 

Not all thin-sets are capable of bonding directly to tile surfaces. Consult setting materials manufacturers for recommended thin-set mortars. In some cases, the surface of the tile to be bonded to must have the surface abraded to ensure a good bond. This should be confirmed with a “bond test”. 


Caution: Mechanical and chemical abrasion can release fine particles into the air. Appropriate safety equipment should be worn during this process.
While a tile-over-tile installation will minimize or eliminate removal & disposal, the new floor level will be ¾” to 1 ¼” higher. Kitchen cabinets, appliances and doorways to the exterior are affected and must be taken into consideration. 

Can tile be installed without grout joints, also called “butt-jointed” tiles ?

It’s technically possible to do a grout-less tile installation, but tiles should NOT be installed without grout joints.
The primary reason to avoid grout-less tile installations is Expansion & Contraction.
Normal expansion & contraction that occurs within assembled buildings causes movement. This movement is accommodated by grout joints that compress and expand during movement. Tile does not have the flexibility to move and if grout joints are not present, tiles are prone to “tent” or lift off the substrate due to movement associated with expansion & contraction. 
The ANSI specification regarding the minimum grout joint size (A108.02-4.3.8): 
“To accommodate the range in facial dimensions of the tile supplied for a specific project, the actual grout joint size may, of necessity, vary from the grout joint size specified. The actual grout joint size shall be at least three times the actual variation of the facial dimensions of the tile supplied. Example: for tile having a total variation of 1/16″ in facial dimensions, a minimum of 3/16″ grout joint shall be used. Nominal centerline of all joints shall be straight with due allowances for hand-molded or rustic tiles. In no circumstance shall the grout joint be less than 1/16″. 
If one of your clients insists on skipping the grout, keep this in mind: the tile industry does not support grout-less tile installations. If you end up in court due to a failure caused by the lack of grout joints, you will not find any support from tile industry experts that may be hired as expert witnesses. Talk the client out of grout-less installations or decline the project. 

Is there a standard that addresses color variation in grout?

There are no ANSI standards that address color variation in grout.
In part, this is because some colors are more prone to uneven color than others due to pigments and the water used to mix grout. Water conditions vary widely throughout communities and there is no way to regulate this. 
Another factor that influences grout color is the tile itself. It may be impossible to allow grout to cure for best color uniformity and still remove it from the surface of the tile. In other words, grout must be removed from the tile surface before the color has a chance to set. 
It is important to manage your clients expectations regarding grout color. Most grout sample chips are plastic, while the most commonly used grouts are cementitious. It’s not possible for two entirely different materials to be exactly the same color. Plastic grout samples are indicative of the end result. They are not exactly like the plastic sample. Explain this to home owners during the estimating and sales process to avoid misunderstandings. 
If color uniformity is vital, epoxy grouts are often the solution. In existing grout installations, the color can be modified with the use of grout colorants. This is most effective with grout that has not been sealed. Grout that has been washed with oil-based soaps can be very difficult or impossible to re-color. In addition to modifying the color of grout, many grout colorants also function as a sealer. 

What is causing the black mildew in my tiled shower and why can I not get rid of it?  

We field this question a couple times a week. There is no quick fix for this. If you are troubled with controlling black mildew where the shower floor meets the shower walls and in corners about 10” to 15” off the floor, this indicates trapped water. 

Over the course of time, poorly constructed shower pans become saturated with water, soap scum, organic matter & bacteria - the perfect scenario to encourage mold & mildew. The trapped water has no way to escape and becomes a perpetual resource for mildew. 

No amount of bleach will solve this problem.

If it is not addressed, it’s very possible that water will start to compromise walls in the adjoining room, often a closet that goes un-noticed. Other tell-tale signs: paint bubbling & discoloration on base boards, stains on drywall, musty odors and damp flooring in the adjacent room. Don’t wait to have this checked by a professional. 


We do not recommend removing the shower floor and replacing it: this shortcut compromises the integrity of the shower substrate. Best to bite the bullet, tear out the faulty shower and construct a properly water-proofed shower. 


Atlantic Tile stocks shower water-proofing systems. Staff can explain how they work and recommend local contractors that are familiar with water-proofing systems.

Can you find a tile that was installed in my home when it was built?

This is one of the most common problems home owners bring us. For decades, countless people have visited our showrooms with a spare tile in hand, desperately searching for the same tile; hoping we have it in stock or just a few boxes lying around our warehouse. 
These forays are typically caused by kitchen renovations. New cabinets have a different “foot print” and home owners are on the hunt for a couple extra tiles to fill in where there is no tile.


Sometimes the culprit is plumbing problems that require sections of tile & concrete slab to be removed for access to under-ground sewer pipes.

How often do we have their particular tile in stock?

Unless the tile was originally purchased from us within a few months, it’s unlikely. Sometimes we can figure out the manufacturer & collection. If we have that information, we contact the factory to find out if the tile is still in production. If it is still produced, we can get the tile. Keep in mind that shade & tone differences, even size differences must be expected. 
How often will you find a couple pieces or boxes of 5, 10, 15 or 20 year old tile lying around any tile warehouse? 
Almost never. 
Here’s why: the lifespan of a tile collection is 3 to 6 years on average. There are some very rare exceptions to this, but generally, if you are looking for a tile that was installed 5 or more years ago, this is likely an exercise in futility.  Think about it this way, when you buy an outfit at Bloomingdales, once they sell out of that season’s stock, you’ll never find that outfit again. Tile trends are a lot like fashion trends. Popular colors & styles, shapes & sizes change over time and manufacturers are constantly refining and modifying tile productions to meet current demands.
This is why we recommend purchasing & keeping extra tile when doing a flooring renovation. Having a few boxes on hand when you need it in the future will save a lot of aggravation in the long run.

We might be able to help you come up with alternative solutions. It’s best to be open minded about this very real possibility. 

What is Moh’s Hardness and how is it relative to tile?

In 1812, German mineralogist, Friedrich Mohs developed a scale to measure the hardness of minerals. This scale is also used to measure the hardness of other materials, including tile and natural stone. The Moh’s Scale uses 10 fairly common minerals of known hardness and assigns them a value from 1 (softest) through 10 (hardest).

Talc has the lowest classification and is the softest mineral on the list at number 1. Diamond is the highest on the list at number 10 and is the hardest mineral known.

Moh’s Hardness Scale






















Compared to Flooring Materials

resilient flooring (vinyl, asphalt tile)

wood flooring

polished marble, laminate flooring

black marble

glazed ceramic tile

glazed ceramic tile 

quarry tile, glazed porcelain tile

unglazed porcelain tile

no flooring is this hard

no flooring is this hard

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