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Flooring and Carpeting/flattening cement slab for tiling


I frequently tile small jobs but this time I have a large area to tile which is approximately 900 sqft. I have not checked the slab yet for flatness. It is a chapel in a large church complex and I am donating my time but I want it to look well done. Can you explain to me how I can accomplish the  correct preparation before tiling. Thank you very much. Also any suggestions as to type of tile to use and spacing would be helpful.

Forgive me for being tardy Bob...I was out of town for a few days.

    Ok first, looking for humps is more important than discovering dips. Dips can be filled as you go when you encounter one (or several) but humps are the ones that can really mess with your install. It can run off your joints in both directions at once and is impossible to recover from until rendered flat. So lets take a long piece of aluminum and tape a four foot level to it. I have a couple cabinet levels that are 8' long that I typically employ for this and I also have a 10' piece of 5" aluminum "L" angle which I can tape my cabinet level to. You can also do the old two block with a string line to check much longer lengths like hallways or walkways inside a Chapel. You just set them up (weighted with the string tied around them (I used to use a couple old weights I used to have) so that the string is held a little taught and suspended above the slap a couple inches and then you can easily use a tape measure to check the space between the string and the floor. Only takes a few minutes and also helps visually as you can usually "see" any humps or "dips" readily. These are the two time tested and proven methods I have employed over the decades when faced with this scenario. So if you discover a hump then you are going to want to "bush" it down which you may already know is a "bushing head" attachment for a Chipping hammer which if you don't have one can easily be rented for about $45.00 a day at your local Rental Center. It will crush the surface of the hump down and you just keep your straight edge handy and check it as you remove material. Once you have it down you can simply flat skim it with thinset and let dry before you begin the install. Of course you will discover a few dips as well so those can be filled the same way by skimming over it with 1/8" layers at a time with the thinset and let dry...I mention all of these details with the assumption that you are going over a cement slab as you mentioned....

   Now as for material suggestions I have long ago moved over into the "large format" tile society...but let me add a small caveat to that. Bigger is better as long as you can eliminate the problems I have discussed above. A large tile can balance "above" the surrounding tiles if not discovered beforehand and with the other jobs you have already done I'm sure you have an understanding about what all that means. I am not a fan of grout joints and if there is a maintenance crew that cares for things I bet they don't like them much either therefore I try to eliminate as much as I can when possible. I did the same thing you are doing for my own local church many years ago and I installed a serpentine Marble with a cross insert. Folks walked over it for two plus decades before they remodeled the church. No one slipped of fell even though it was a polished stone. Most folks do not run in or out of church (safe to say) so I think the selection platter is wide open to you. Joint spacing for me is always as small as possible typically 1/8" on average wholly depending upon how well you are able to prep the sub-strate. With so many people in or out perhaps you might consider a Porcelain tile for the durability factor and many new examples have some texture with it if you are concerned with anyone slipping. I recently did a couple installs using the wood plank Porcelain copy that was 4" x 33" and the other was 6" x 24" both turned out great though the 33" example was more challenging when running into suspect portions of the sub-strate. I ran them "jamb joint" tightly together and grouted with a "non-sanded" grout. So there you go Bob, I hope this helps you with your project and cudo's to you for "giving as onto the Lord" with your heartfelt donation with the work of your hands. Forgive me being late again and please feel free to return anytime...

Perry V.

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Perry Vellenga


Ceramic Tile/Marble. I can answer questions about floor preparation, tile selection, layout questions, performance of products, expectations of finish, compatabilities, questions about grout and epoxies, evaluating an installer, asking the right questions to check competence...more? 33 years this August 2012/ many years in commercial application from exterior finishes to Mall store fronts/ interior finishes like floor packages in stores inside Malls examples: The Limited, Lerner/NY, Lane Bryants, Bombay Co., Now involved in Residential new construction covering all types of interior finishes and designs.


I worked in an exclusive field of floorcovering called "Tenant Development" which is by invitational bid only, by way of a National bid list. These are large floor packages usually over 3500 sq. ft. of 18" x 18" Marble and Granite and many other types of Marble and sizes. They are specialty stores where the floor package can cost upwards of $50,000 for one store. I have also done "Structure" stores and J. Riggins stores, Lane Bryant,Express and Body Shop stores where wood flooring is used. Presently work for a National Flooring Company in the Residential new construction arena that covers most interior design elements..Granite Slab tops/wood flooring both job finished and prefinished ect..

My response's are published all across the Internet and picked up by multiple Interior Design sites and Industry related web sites where people have questions...

too many most of which don't count...

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