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TB87

GROUT JOINT WIDTH: WHAT IS THE RIGHT SIZE?

Technical Bulletin

Technical Services 800-282-8786

custombuildingproducts.com

All ceramic and natural stone tiles are installed with a

gap or space between each tile in the assembly. This

is generally referred to as the grout joint. However, the

required width of a grout joint is not always

understood. ANSI defines the requirement for grout

joints in ceramic and natural stone tile installations in

A108.02 Section 4.3.8. This section states that under no

circumstances should the grout joint be less than 1/16"

(1.6 mm).

Due to the amount of size variation in the tile, the

actual grout joint width may need to vary from what is

requested or specified. The actual grout joint size

should be equal to three times the variance in actual

tile facial dimensions. This means that if the variance in

facial dimensions of the tile is 1/8", the actual grout

joint will need to be 3/16". The wider spacing will help

to accommodate placement of tile and maintaining

straight lines.

TCNA recommends a minimum 1/8" grout joint for

rectified tile and minimum 3/16" grout joint for

calibrated tile. They also suggest adding to this width

the amount of edge warping on the longest edge. For

example, if the edge warping of a rectified tile is 1/32",

the minimum grout joint is 1/8" + 1/32" = 5/32".

To minimize lippage, TCNA also recommends no more

than a 33% offset for tile greater than 18". Large format

tiles (those with one or more sides longer than 15")

should be installed in a running bond or brick pattern,

especially if the tile is plank-shaped.

Where is the right place to measure the width of the

grout joint? With cushion edge and beveled edge

tiles, some will argue that the measurement is at the

surface of the tile or the widest point of the bevel. This

may minimize the grout joint appearance, but the joint

between the tiles is now too narrow to accommodate

proper filling and curing of the grout. The grout joint

width measurement should be taken at the base of the

bevel or at the body of the tile. ANSI states in A108.10

Section 5.3 that grout joints between cushion edge

(beveled) tiles should be finished evenly at the depth

of the cushion (bevel). This implies that the minimum

1/16" joint width is measured at the base of the cushion

or bevel.

Some tiles have lugs or tabs built into the edge of the

tile to assist in even spacing. If these lugs do not

produce a grout joint in compliance with TCNA

recommendation, additional separation may be

needed. Also, the space between the lugs and over

the lugs may not be sufficient for proper curing of the

grout and can result in powdery or discolored grout.

Extra care must be exercised when installing tiles with

spacing lugs on the edge.

Why is adequate grout joint width so important? First

and foremost, it will prevent tripping and breaking the

edge of the tile. By increasing the spacing between

the tiles, it reduces the slope of the transition from one

tile to the next tile. The wheels of carts roll freely over

the tile surface and shoes are less likely to catch on a

tile edge. Wider grout joints allow the installer to force

the grout deeper into the joint between tiles,

completely filling the grout joint. The larger mass of

grout will cure more completely and result in a harder

grout joint. Grout that is placed in joints that are too

narrow will be powdery and generally discolored.

Before the tiles are set, the required grout joints should

be discussed with the customer and agreed upon.

Properly spacing the tiles and selecting the correct

grouting material will assure an attractive, safe tile

installation that will last for years.

The information in this bulletin is presented in good faith, but no

warranty,

express or implied, is given nor is freedom from any

patent in as much as

any assistance furnished by CUSTOM with

reference to the safe use and disposal of its products provided

without charge. Custom Building Products assumes no obligation or

liability therefore, except to the extent that any such assistance shall

be given in good faith.

Summary of content (2 pages)

PAGE 1
TB87 GROUT JOINT WIDTH: WHAT IS THE RIGHT SIZE? All ceramic and natural stone tiles are installed with a gap or space between each tile in the assembly. This is generally referred to as the grout joint. However, the required width of a grout joint is not always understood. ANSI defines the requirement for grout joints in ceramic and natural stone tile installations in A108.02 Section 4.3.8. This section states that under no circumstances should the grout joint be less than 1/16" (1.6 mm).
PAGE 2
TB86 TILE INSTALLATIONS WITH GROUT JOINTS LESS THAN 1/8-INCH WIDE Traditionally, tile or stone grout joints measuring more than 1/8" wide were filled with a grout including an aggregate – sand. Grout joints less than 1/8" were filled with a “non-sanded” grout and 1/16" was the smallest joint recommended for tile installations.