tiling a bathroom floor

8/10/2019 Tiling a Bathroom Floor

1/6

BY DENNIS HOURANY

st ofs in the

forminge layout.

help.

T iling a Bathroom

FloorCementitious backerboard speeds up the job,but start with a subfloor that is firm and flat

f anything can beat ceramic tile fora bathroom floor, I'd like to know

what it is. Durable and nearly im-pervio us to water damage, tile also is adaptable to just about any architectural style. The

ceramic-tile industry now offers an incredi-

ble variety of tile, as well as reliable materialsfor setting it. If tile is more expensive thansome other floor coverings, it can last as long

as the house with little upkeep.True enough, but a tile floor can be a

nightmare if it is not laid out and installed

carefully on a well-prepared subfloor. One othe key early considerations is the substrate

on which the tile will be installed. Floating amortar bed at least in. thick used to be

the only choice. Now we can use quick-to-

install cementitious backerboard.As for the tile itself, durability and smo oth -

ness are of major concern. Most tile manu-

facturers rate their tiles for durability by clas-

Is the floor stiff

enough?A dial indi-cator attached to a

length of iron pipe is

one way to check

whether there is too

much deflection in

the subfloor. A

bouncy subfloor willresult in cracked tileor grout.

1

I

Set full tiles wherethey are most visibleA diagonal tile layout in this small bathroom lookbest with full tiles or complete half-tiles in fronthe tub and the vanity, the two most visual arearoom. Using these references, two control linesa 90 angle are the starting point for an attractivGrid lines taken from the control lines also can


2/6

sifying them as either residential, commer-

cial, light industrial or industrial. For a bath-

room at home, the residential grade is justfine. Smoothness is rated on a numerical

scale measuring the coefficient of friction, or

COF. Even though the roughness scale goes

all the way to 9, I've found that a rating of0.6 provides good slip resistance. Just keep inmind, though, that the COF goes down

wh en the tile is we t. If you don 't find the

COF specified on the tile box, you can call

the manufacturer for the information.

Make sure the subfloor is flat

Setting tile on an inadeq uate subfloo r is beg-

ging for trouble. The subfloor should meetdeflection criteria set by the Tile Council of

Am erica (P. O. Box 1787, Cle mso n, SC29633; 864-646 -8453; www.tileusa.com)in other words, it can't have too much

bounce. If it does, chances are good the tile

will los e its bond with the bac kerb oard , o r at

least that grout joints between the tiles will

crack. The Tile Council allows a maximumdeflection of of the span, or the span in

inches divided by 360. For example, if you

have a span of 48 in., the most sag the sub-

floor can show under a load is 0.13 in., orroughly in. Although the Tile Councilcalls for a minim um -in. exterior-grade

plywood subfloor, houses where we set tile

often have subfloors of -in. oriented strandboard, and we haven't had any problems.Minimum joist spacing is 16 in. o. c.

I can sense whether there is too much

bounce simply by walking around on a floor.

That's after setting hundreds of tile floors.Wh en I sta rte d, tho ugh, I me asure d the de-

flection with a length of iron pipe and a dial

indicator just to make sure (photo 1). If

there's too much deflection, don't go any far-ther without fixing the problem.

The subfloor also must be flat. Here, themaximum amount of leeway is in. in 10 ft.

That means if you were to lay a straightedgeon the subfloor, you should not be able to see

a hump or a dip that exceed s in. A wavy

floor can be corrected. One way is to use a

leveling compound over the wood subfloorbefore the backerboard is installed. You can

also put the backerboard down first and then

use a leveling compound that bonds to it.

In either case, the application is the same.Using a straightedge,pull some levelingcompound across

the low spots to

fill them in.You may

need to

use morethan oneapplica-

Clean-cutting backerboard.The authoruses HardiBacker, a -in. cementitiousbackerboard, as a tile substrate. Scoredon one side with a carbide tool, the boardwill snap cleanly with no back cut.

Glue for the backerboard.Theauthor uses a type-I mastic tobond the backerboard to theoriented strand board subfloor.An acrylic-modified thinsetmortar also could be used.

Nail it down.Galvanized roof-ing nails in. long should bedriven 6 in. o. c. to install thebackerboard. Set nail headsflush with the surface.

2

3

4


3/6

tion. Leveling com pound s are typically avail-

able from tile suppliers.

When installing backerboard, don'tforget to leave an expansion gap

Cementitious backerboard is made by sever-al manufacturers, and it is readily available.

We us e -in . HardiBac ker (J am es Har dieInterior Products; 800-942-7343). Sheetscome in several sizes. I like this product a lot

more than the backerboard with fiberglassmesh on each side. HardiBacker cuts cleanly

and easily (photo 2, p. 87), and it's simple to

fasten to the subfloor. The -in. thickness

makes it easy to keep the tile at the rightheight, without framing a recess into thefloor or having an awkward lip where the tile

meets a nother floor surface. However, if you

need to raise the level of the floor to meet an

adjoining surface, you could use -in. ce-

ment board.

I cut and lay out all the floor's backerboardbefore nailing any down. When it's laid out,

joints should be staggered, and edges shouldoverlap subfloor joints. It is imperative that

yo u le av e a -in . ex p an si o n ga p be tw ee nsheets and a -in. gap at perim eter walls orother restraining surfaces, such as cabinets.

Most manufacturers require that thebackerboard be bonded to the subfloor with

an adhesive, and we use type-I mastic. You

can use thinset adhesive. But the masticworks ju st as well in this application, and it'sfaster and easier to apply (check with the

backerboard manufacturer before decidingwhat to u se) . Whatever the adhesive, putit down evenly with the notched trowelrecommended by the manufacturer,

and don't apply any more adhesivethan can be covered withbackerboard before it skinsover (photo 3, p. 87). I use

-in. galvanized roofing nails driven intothe backerboard every 6 in. (photo 4, p. 87).Nail heads sho uld be flush with the backer-board, and if the floor is anything but tiny

you 'll find a pn eu mat ic naile r is a big helpWe don't use screws because Hard iBacker

does not require them and because they aremuch slower to install.

Set control lines for laying the tile,

and cut the odd ducks nowWhen beginning a layout, I start by

checking that walls are square andparallel. If you find things are seri-ously out of whack and will causemany small tiles or unsightly cuts

you may con sid er insta lling th e tile

on a diagonal. That's what I did

here, although the reason was to

add a little interest to the floor, notbecause the room was out of

Cut crucial tileswhile the floor isdry.Before apply-ing thinset to thebackerboard, theauthor lays out thefloor and cuts tilesto go around ob-structions, such asthis closet flange.

A wet saw worksbest.A tile saw isthe most versatiletool for cutting tile.Curved cuts startwith a series ofstraight cuts to thelayout line.

Nippers finish thejob.After the authormakes a rough curvedcut with a wet saw, heremoves the wastewith tile nippers.

Stir the thinset with a slow-speed p addle.A mixing paddleturning at between 300 rpm and400 rpm does a good job of stir

ring up a batch of thinset. Itneeds to be allowed to

slake, or rest, for 15 min-utes before it can be

used to lay tile.

5

6

7

8


4/6

square. Diagonal layouts also have the effectof making a narrow room appear wider.

Most every room has obvious focal pointswh ere ful l tiles sho uld go. I esta blis h two

control lines, 90 to each other, and orientthem so that they correspond with theroom's focal points. For example, in the smallbathroom I'm tiling here, the two critical

points are in front of the vanity and in front

of the bathtub; I plan on using full tiles (or

complete half-tiles) in these areas (drawingp. 86). Cut tiles will go where they are less

obvious. In general, I try to avoid cuttingtiles to less than half their original size

they just look unsightly.Aft er you've determi ned the bas ic layout

and the control lines, you can snap grid lines

that will guide you as you set the tile. Plastic

spacers will keep your grout lines a consis-tent width. But don't count on them entirelyto keep the layout straight because tiles vary

somewhat in size. Follow the layout lines, no

matter what, for straight grout lines.

I think it's a good idea to cut some tile inadvance while the floor is still free of adhe-sive. I don't cut all of them, just those aroundthe closet flange or other oddly shapedspaces (photo 5, facing page). Once you getto a point where full field tiles (or cut tiles of

a uniform size) will be used, cutting and fit-

ting them in advance isn't necessary. To cut

tile, I use a tile saw and a pair of nippers(photos 6 and 7, facing page). You could usea tile board, which works by scoring andsnapping tile much as you would cut a piece

of glass (thes e tools also are called snap cut-ters). One disadvantage of a tile board,though, is that it can't cutL and Ushapes.

You can use a grin der w ith a dia mo nd bla de

or a jigsaw with a Carborundum blade tocut tile. However, it 's more difficult, andthe cuts are not as clean.

You can't go any f urt he r witho ut m ixi ng up

a batch of thinset mortar, which is used tobridge the seams in the backerboard and toglue down the tile. I use acrylic-modified

thinset no matter what the substrate. It pro-

vid es a bette r bo nd , of fers more flex ibil ity

and stays usable in the bucket longer. Som ekinds of tile require different thinset

additives, so

be sure

Tape seams now toavoid cracks later.Fiberglass-mesh tapebedded in a thin lay-er of thinset spansthe gap between ad-joining sheets ofbackerboard. Skip-ping the tape cancause cracks to de-velop later.

Apply an even layer of thin-

set.The author uses anotched trowel to spreadacrylic-modified thinset forthe tile, taking care not to ob-scure layout lines.

Bed the tile in thinset mortar.Whenyou're setting tile, plastic spacers willkeep grout joints uniform in width, butfollowing control lines is a better guaran-tee that grout lines will be straight.

Check the thinset.After set-ting a few tiles, lift one up tomake sure they have enoughthinset. Large tiles such asthis one may need to be back-buttered to get full coverage.

9

11

10

12


5/6

to consult your supplier to make sure that

you have the rig ht kin d.

Preparing thinset requires precision

Wh en mixin g thin se t, follow the dir ect ion s

on the bag to the letter. One requirement isthat the mixture slake, or rest, in the bucket

for 15 minutes after the initial mix. Thenmix it again before use. Occasional stirring

may help to keep the thinset workable, but

don't add any more acrylic admix or water

much after the second mixing. We use a-in. drill to turn a mixing paddle at be-

tween 300 rpm and 400 rpm (photo 8, p. 88).

Taping the joints between pieces of backer-board helps to prevent cracks later. We usefiberglass mesh tape 2 in. wide, bedding it in

a layer of thinset (photo 9, p. 89). Make sure

that seams between sheets are completely

filled. After you apply the first layer of adhe-

sive and tape, you'll need to put down anoth-

er layer of thinset over the tape with the flat

side of a margin trowel, holding it at a 45

angle and pressing the tape firmly into thethinset. If you tile the floor in the same day,

you can tape as you go so that you won't walkor kneel in wet adhesive. But if you wait

overnight, make sure no t to leave any lumpsof thinset at the seams.

When applying the thinset to the backer-

board for the tile, use the notched side andhold the trowel at 45 to the floor so that an

even amount of adhesive is applied and noair is trapped (photo 10, p. 89). What you

wa nt is 100 % cov era ge of both the backer-

board and the back of the tile, with about

in. of thinset between the two surfaces.Large tiles may have uneven backs, which

wil l requ ire you to ba ck -b utte r the su rfac e

with the flat side of a tro wel. Place the tile on

the thinset with a slight twisting mov ement

to help embed the tile fully (photo 11, p. 89).

It's also a good idea to pull a tile off the floornear the start of the job to make sure you're

using enough thinset. If the back of the tileis not fully covered, you'll know to adjus

you r techn iqu e or trowel or b oth (ph oto 12

p. 89), assuming the thinset has been mixed

properly. Look on the label of the bag thethinset comes in for the proper notch size.

If, after a while, the thinset becomes too

stiff or if tile doesn't readily s tick to it, throw

it away and mix a fresh batch. Before the

thinset dries completely, you should cleanthe excess from the joints (photo 13, below)

If you don't, the grout may be too thin, or iwill hyd rate une ven ly, two con dit ion s tha

make a weak grout line.

For a high-strength job, don'toverwater the grout

Grouting can make or break the tile job. Acommon mistake is adding too much water

Clean out the excessthinset. A margintrowel is a perfecttool for removingthinset that hasoozed into the grout

joint. If grout doesn'tget all the way intothe joint, the result-ing bond will beweak.

Grout mix shouldbe stiff.Holding agrout trowel at a45 angle, the au-thor works a stiffgrout mix into

joints betweentiles. Excess grout

should be trow-eled off as you go.

13

14

Does a tile look o ff?Take it out and reset itA day after setting the tile in this bathroom floor, I re-

turned to apply the groutand staring me right in the face

was the corner of one tile that had sunk below its neigh-

bors. Although the toilet would have camouflaged theproblem, it was better to fix it before going any further.

Pulling a tile is not a big deal, p roviding you get to it be-

fore the thinset adhesive has had a chance to cure fully. In

this case, the acrylic-modified thinset had been applied theprevious after-

noon, and it was

still green. Using

a hammer and a

steel bar, I was

able to jar thetile loose with-out too much

trouble and

without breaking

the tile. After

scraping thesemicured thin-

set off the back

of the tile and

the floor (photo

left), I appliedfresh thinset to both surfaces and rebedded the tile. Thistime, I was careful to keep the tile flush with the those

around it. This repair didn't take more than a few minutes,

and as soon as the tile was reset, I grouted the entire floor.

You never would have known anything was amiss.

D. H.


6/6

or admix when mixing the grout, which

causes discoloration and a weaker mix. An-

other is using too much water when cleaningexcess grout off the tile, which also can cause

it to discolor. A third common error is usinga high-speed mixer for the grout, which

traps air in it and makes it weak.Add only eno ugh wate r to the grout pow-

der to make it workable. Follow the manu-

facturer's recommended ratio of water togrout. Ideally, the grout should be a lit-

tle difficult to spread into the joints. Ifyou 're no t going to mix the gro ut by

hand, use a mixing paddle, the same

type you would use for m ixing thin-set, and a slow-speed drill. Aftermixing, allow the grout to slake for

15 minutes and then remix it. At

this point, you may add liquid or

powder to adjust the consistency.As you w ork, rem ixin g t he grou t

occasionally will help to keep it workable,

but do not add more liquid.Use a rubber grout trowel to spread the

grout diagonally, holding the trowel at a

45 angle (photo 14, facing page). GroutKing makes the best grout trowel I know

(Diamond Tough Tools; 888-595-5995;cost: about $13), It's worth buying oneeven if you use it only once.

Wit h all the joints

filled and excessgrout re-

moved with the trowel, let the grout sit until

it begins to firm and you see a dry film on

the tile. Then it's time to began cleaning thetile. You'll need at least two good hydro

sponges (sold at tile-supply stores) and a

large bucket of clean, cool water. After wet-

ting and wringing out the sponge, wipe thesurface to get even grout joints. Then, with a

rinsed sponge, use one side of the sponge fo r

one wipe in a diagonal direction (photo 15,

below). After using both sides of the sponge,wrin g it out (ph oto 16, below ). Chang e thewater frequently to avoid spreading dirty wa-

ter on the tile. You ma y have to make severalpasses until all the residue is gone.

After the floo r dries, you w ill s ee a fi lm onthe tile surface. This film can be polished off,

but wait a bit until the grout is firmly set.

D e n n i s H o u r a n y o w n s E l i te T i l e i n W a l n u t C r e e k ,C a l i f o r n i a . P h o t o s b y S c o t t G i b s o n .

When a film appears, startcleaning.Not long after grouthas been applied, a hazy filmappears on the tile. That's a sig-nal to start wiping the floorwith a clean, damp sponge.Keep the pressure light.

This sponge needs a dunk.Af-ter a single light pass across thefloor, this sponge has picked upplenty of excess grout. The au-thor flips the sponge over,makes another light pass andthen rinses out the sponge.

16

15

tiling a bathroom floor

Documents