"a practical hands-on
   guide to bathroom


Flooring Installation

Most important:  Never ever rush a floor installation.

Now that you have removed the old flooring, you must be certain that the subfloor is structurally sound - ugly is o.k. but it must be sound.  Never rush the prep because it may reflect in the final quality of the floor.

Be certain the floor joists are structurally sound.  If they are not, they may need to be replaced or, more commonly, new structural members can sandwich the old joists.  If you do sandwiching, I suggest you use the same size joist material (for example - 2" x 10"s) and then bolt them together with 3/8" carriage bolts (for example - 5" long) with washers and nuts. 

It is best that floor joists be on 16" centers.  If they are not or if the joists are not structurally sound, you should consider building a ladder between the joists.  A ladder is nothing more than the same size joist material cut to fit perpendicular between the existing floor joists and held in place by metal joist hangers and screws.  I like screws because they hold much better and if you make a mistake you can easily remove them. 

The subfloor material should be 5/8" exterior grade plywood - 3/4" would be even better.  If

the old floor is 1/2" plywood with only a small portion requiring replacement, use 1/2"
plywood instead of removing the entire floor.  A judgement call is required here, keeping in
mind that if the floor has any flexing, it will eventually cause the tile floor to fail.  The subfloor
must be structurally sound, even if it means adding a second layer of plywood. 

Next you need to install a 1/4" or 1/2" cement backer board.  See what is available in your market before deciding on which cement backer you use.  Please be aware this will increase or decrease the transition from the new tile floor to the adjacent floor.  Metal floor profiles (threshholds) are used most frequently at the point where the tile ends and the adjacent floor begins.  Do not use cultured marble or natural marble threshholds (if possible) because they scuff and are subject to cracking.  Fasten your backer board to the subfloor with corrosion resistant 1-1/4" or 1-1/2" screws (depending on the thickness of your backer board).

Next think about what pattern you want in the floor tile design. The basic crossword puzzle pattern is fine, but also consider a staggered brick pattern or a 45 degree angle design (this will require much more work as well as additional tile waste).  Determine where the longest
straight wall is located and where the line of sight goes when looking at the floor.  I don't

suggest starting with a center line in the floor because if the wall is grossly out of square it
will be evident as one looks at the floor (it is not as evident if the tile is laid on a 45 degree angle which is why a lot of contractors like to lay tile in that pattern).  The staggered brick pattern is now a popular choice that many people like and is somewhat timeless.

Lay out the entire floor dry with appropriate plastic tile spacers which are a must for even tile spacing (spacers must be removed after the tile floor has dried for a least 24 hrs and BEFORE GROUTING).  Some types of tile require cutting with a wet diamond saw while other types may be cut with a hand cutter (this depends on the hardness of the tile).  Diamond drills may be needed for unique cuts, but this is seldom the case.  Use safety glasses when cutting tile with a saw or drill.  Most of the needed tools may be purchased or rented from your tile supplier and some suppliers will even loan you the tools.

Always use good quality "fresh" latex fortified mortar (a little more expensive but a MUST to
avoid tile failure).  Do not use old mortar from a special price sale - it may be bad and will

possibly cause significant tile failure.  The temperature in the work area should be between
50-100 degrees F and out
of sunlight if possible (since this will cause premature skinning or drying of the mortar).  Spraying the mortar with a mister may be acceptable, but check with the mortar manufacturer first.  The mortar should be mixed with a low rmp mixer for about five minutes - add water slowly (you can always add more but you can't remove it and you don't want watery mortar).  Let the mortar slack (sit) for about 10 minutes and then remix for a few minutes (not much more).  For 12" x 12" tile - the most popular as of this writing - use a 1/4" x 1/4" x 1/4" square notched trowel.  Use the smooth side to spread the first application to the backer board and then the notched side for the application to the tile.  Lay the piece of tile and then remove it to make certain you are getting a good bond of mortar to the tile (otherwise the tile may fail/crack).  If you are not getting good contact, change the angle of your trowel to get a higher mortar bed. 

As you lay the tile, keep the spacers in place and use a beating block to set the tile in the mortar bed.  If some mortar oozes between the tile, remove if immediately since it is difficult

 to remove once the mortar sets up.  Also, you may damage the tile in attempting to remove
the ooze once it sets up.

I don't like to reuse wood trim if possible - I prefer to use 3" x 12" tile trim caps (to match the floor) which are available in most (not all) tiles made.  Another alternative is to cut the field tile and make your own trim, but it will have an unfinished edge on the top.  It is best to install the tile trim after the floor has set up (overnight) using 100% silicone caulking to "glue" the trim to the wall.  This makes for a professional look.  Tile trim is also a LOT easier to clean than wood trim.

Next you are ready to grout the floor.  Always use good quality fresh sanded grout - unless you are installing highly polished tiles or natural marble - then use unsanded grout with narrow grout joints.  Sanded grout will scratch polished tile.  Latex additive is sometimes added to grout to give it additional strength, but care must be taken since the open time and set up time can be quite short.  If the latex grout is not wiped clean in a short period of time, it may be almost impossible to remove.  I do not recommend the latex additive for the nonprofessional - the advantages are not worth the potential trouble.  Force the grout in between the joints with a rubber float held on a 45 degree angle.  Wipe away the excess
grout with a damp but NOT WET sponge and strike the grout joints with a striking tool or
an old metal spoon (be certain the metal spoon doesn't etch the tile).  Striking (smoothing
out the grout joint) makes the grout look more attractive and gives it a more durable finish.  DO NOT introduce too much water into the grout with the wiping sponge since this will cause the grout to shrink and give the appearance of cracking.

Once the floor grouting is complete, you may grout the wall trim/baseboard.  Then wipe down the entire floor with clean water.  Final washing with water and cheap vinegar (cup of vinegar to two gallons of water) will remove grout film from the tile.  Several washings may be necessary to get the film off some types of tile.

You are then ready to reinstall the toilet, vanity, pedestal sink, floor registers, etc.  Normally,  clear 100% silicone caulk is used where tile meets the floor.  A judgement call needs to be made on the color - either clear or white silicone caulk is acceptable. 

Leave the new floor undisturbed for a couple of days to allow the grout to cure.  Heavy traffic areas should cure for a week or more.