- INTRODUCTION
- In 1966, Ceramic Tile Institute issued Field Report CTI 66-2-5, "Waterproof
Membranes for Shower Floors", and still has it on the Table of Field Report
List. CTI 66-2-5 outlines the hot mop method, which has proven to perform well
when used for shower floors, and roman tubs. CTI 66-2-5 is for the hot mop membrane
only, but this does not preclude the use of other adequate membranes being used
in shower areas.
- In 1977 Ceramic Tile Institute issued Field Report CTI 77-2-2, "Thin
Water Proof Membranes", and it is still on the Table of Field Report List.
This report covers the trowel-on thin membranes and their use as both a waterproof
membrane and cleavage membrane for use over cracked concrete.
- A review of CTI 66-2-5 and CTI 77-2-2 revealed that although both of these
reports covered their subjects quite well, additional information was needed
on three items:
- Waterproof membranes for use on roof decks where tile is installed over
the membrane in a wire reinforced mortar bed.
- Manufacturers information on underlayments used to level out the concrete,
both prior to the application of tile in the thin-set method, and where a thin
trowel-on membrane is to be applied to which the tile will be bonded.
- Manufacturers information to evaluate the various kinds of thin membranes
where the tile is going to be bonded directly to them.
- DISCUSSION: Waterproof Membranes for Roof Decks
- The tile trade relies on the roofing trade and the manufacturers of waterproof
membranes for technical information on waterproof membranes for roof decks.
- roblems with this type of membrane have been minimal and CTI is only looking
for technical data on good membranes that can be given to the architect
and specifier when they request it.
- UNDERLAYMENTS FOR THIN-SET MORTAR INSTALLATION
- There are some good underlayments, but the ceramic tile trade has experienced
considerable trouble with underlayments. One problem has been a lack of bond
between the underlayment and the concrete. Another problem has been where the
underlayment is soft and chalky instead of being cured out firm and hard.
- There are a number of different types of underlayments;
directions on some say to just add water and some say to add a white latex liquid
instead of water.
- Some underlayments are trowel on materials and some are self-leveling materials.
- Some manufacturers of thin-set bonding mortars recommend their bonding mortar
as the underlayment.
- THIN MEMBRANES TO WHICH TILE IS TO BE BONDED
- There has been good job site installation experiences with some of the thin
membranes on the market that have been specifically designed to have tile bonded
directly to them. They have been installed and have performed for long periods
of time.
- It is important to have this performance installation experience rating because
of the difficulty of proving the membranes out through a testing program.
- There have also been some tragic failures where the
membranes and the bonding mortar are not compatible and the tile have lost bond.
- When these failures are studied, it is usually revealed that there is no
bond between the bonding mortar and the membrane. It is also revealed that there
is no experience in the use of the membrane in successful installations. Finally,
it is found that the membrane used was not designed to be used in a thin-set
installation system.
- CONCLUSION
- When tile is going to be installed on exterior decks, the waterproof membrane
becomes the insurance policy that makes the entire installation perform. Under
many of these exterior decks are rooms containing files, vital records, books,
and also expensive office equipment, including computers. Therefore, no compromise
should be accepted for installing the best and most durable waterproof membrane
possible.
- When ceramic tile is to be installed in the thin-set method, over a concrete
slab, and underlayments are needed, only the best should be used. Correct concrete
slab preparation, underlayment mixing, placing of the underlayment and curing
of the underlayment are of vital importance. It must be realized that the bonding
mortar is going to be bonded to the underlayment and not to the concrete. If
the underlayment is not bonded to the concrete, or if the underlayment is soft
and uncured, the entire installation is lost.
- When thin membranes are used over concrete slabs, a membrane should be selected
that is part of a total system. The system should be one that has an excellent
experience rating. To the best of our knowledge, failures have occurred where
urethane membranes have been installed that are not part of a total system.
There is also a lack of successful experiences where the urethane membrane and
a different manufacturers bonding mortar were used and failed. Use a total system
with a proven successful experience rating.
- Hot mop asphalt membrane for roof deck over which tile is to
be installed in the wire reinforced mortar method.
- Membrane shall be built-up on-site and shall consist of not less than three
(3) layers of standard grade fifteen (15) pound asphalt impregnated roofing
felt, ASTM D226. The bottom layer shall be spot mopped to the rough deck with
hot asphalt and each succeeding layer thoroughly hot mopped to that below, on
the basis of twenty (20) pounds of asphalt per layer per square. Asphalt designation
ASTM D312: All base flashing shall be carefully fitted and shall be made strong
and water tight by folding or lapping and shall be reinforced with suitable
woven glass fiber webbing producing a tear strength of not less than fifty (50)
pounds per square inch in either direction, ASTM D2178, and shall be hot mopped
into place. A cap sheet of fifteen (15) pound or greater felt shall be loosely
laid over the membrane as a protection sheet.
- Uniform plumbing code requirements for shower floor and roman
tub membranes.
- Installation
- Drains - An approved type drain with sub-drain
shall be installed with every such shower membrane. Flange of each
sub-drain shall be accurately set exactly level with sloping sub-floor
and shall be equipped with a clamping ring or other approved device
to make a tight connection between the membrane and the sub-drain.
The sub-drain shall have weep holes into the waste line. The drain
shall be of such design that there will be not less than 2" depth
from the top of the sub-drain flange to top of the strainer. A ring
of absorbent material must be placed around the weep holes to keep
them open when the finish materials are installed.
- Sloping Sub-Floor and Membrane - All lining materials
shall be pitched on quarter (1/4) inch per foot to weep holes in the sub-drain
by means of a smooth and solidly formed sloping sub-base. All such lining materials
shall extend upward on the side walls of the tub to a point not less than (4)
inches above the top of the finished dam or threshold and shall extend outward
over the top of the rough threshold and be turned over and fastened on the outside
face of the rough threshold. All ledge tops within four inches above the rough
threshold shall be covered with the lining material. Non-metallic sub-pans or
linings shall be built-up on the job site and shall consist of not less than
three (3) layers of standard grade fifteen (15) pound type asphalt impregnated
roofing felt. The bottom layer shall be mopped to the formed sub-base with hot
asphalt and each succeeding layer thoroughly hot mopped to that below, on the
basis of twenty pounds of asphalt per layer per square. All corners shall be
carefully fitted and shall be made strong and watertight by folding or lapping,
and each corner shall be reinforced with suitable woven glass fiber webbing
hot-mopped in place. All folds, laps and reinforcing webbing shall extend at
least four (4) inches in all directions from the corner and all glass fiber
webbing shall be of approved type and mesh, producing tear strength of not less
than fifty (50) pounds per square inch in either direction. Non-metallic shower
sub-pans or linings may also consist of multi-layers of other approved equivalent
materials suitably reinforced with glass fibers and having each layer carefully
fitted and hot mopped in place on the job site as elsewhere required in this
section, according to manufacturer's recommended installation procedures. Linings
shall not be nailed or perforated at any point, which will be less than one
(1) inch above the finished dam or threshold.
Where lead and copper pans are used as membranes, the installation shall be
made in similar manner as required for felt membranes except the asphalt mopping,
and in addition the pans shall be insulated from all concrete and mortar surfaces
and from all conducting substances other than their connecting drain by 15 Ib.
asphalt saturated felt or an approved equivalent, hot mopped to the lead or
copper pans. Joints in lead and copper pans shall not be soldered, but shall
be burned or silver blazed respectively.
- Tests - Upon installation, all waterproofing shall
be tested for water tightness by being filled to the top of the rough
threshold with water for 24-hours to establish their water tightness
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