WARPAGE AND LIPPAGE OF STONES

Before we start, let see some of the site images regarding the warpage – lippage of stones:

Some type of stones after installation and when get contacted to moisture OR heat they expand, and when they get dry OR cool they contract. Due to this volumetric expansion & contraction, the stones tend to WARP.

It is not necessary that the whole body of the stone needs to be get contact with moisture OR heated to warp. Say, if the bottom of the stone gets in contact to the moisture, and the top surface get contact with the heat, stone tends to warp. And sometimes, if the whole body gets moisture and in the process of drying, the top surface get dries before the bottom dries, then stones may tend to warp.

Here we need to notice, that what happens to the stones still not installed but to be installed? Stones stored at places where temperature variation / moisture attack is possible, stones tend to warp.

Moisture present in the substrate and installation materials plays major role in warping of stones. Warping is the biggest problem with a moisture sensitive stones that too when rate of expansion and contraction between the bonded, wet side of the stone, is lower than that of the exposed top surface. Warping can be seen in green marbles, slate stones and artificial stones.

Two are effects shall be considered in this scenario are the efflorescence and water borne mineral staining in the moisture sensitive stones.

There are many standards which classifies the stone and tile as per the moisture sensitivity.

EN 14617-12 - measure and determine this dimensional instability or warping in three classes and are as follows: Class A: <0.3mm, Class B: 0.3mm < / < 0.6mm and Class C: > 0.6mm.

IS 4457, explains the quality requirement of the stones to be maintained in terms of surface flatness i.e. Centre curvature, edge curvatures and the warpage. Refer to the below table:

Let see the how to test the warpage of the stone as IS 4457:

There is one more factor which may create the confusion in deciding the warpage of the installed stone, without removing it, i.e. LIPPAGE.

As per ANSI (American National Standards Institute) standard A108.02, Section 4.3.7, Lippage means the differences in elevation between edges of adjacent stone / tiles. Lippage is the results of bad workmanship, warpage of the stone, spacing width of the stones, reflectance of the surface and expansion & contraction of the substrate on which stones / tile has been installed. 

So, to conclude the warpage of the stone, stone needs to removed, thickness at the edges shall be measured including the flatness of the stone.

The stones which are of Class B and C requires special type of adhesives. i.e.

1.  Cementitious adhesive with moisture sealer coat applied on all surface of the stone expect the top surface.

OR

2.  Cementitious fast setting deformable adhesive.

OR

      3.  Epoxy based adhesive.

But, ANSI A 108:19-2017 says:

Lippage shall be mentioned 

Maximum allowable lippage is 1/32 in. (0.8mm). When installing multiple gauged porcelain tiles or gauged porcelain tile panels/slabs with any side greater than or equal to 39 in. (1 m), lippage control systems are required.

FEW POINTS ON LARGE FORMAT TILE / STONE INSTALLATION

From 2000, trend of using of large format tile / stone has become very popular in interior decoration and external aesthetic. There are many advantages in using large format tile / stone for customer as well as installer.

a. Large format tile / stones provide the feeling more spacious room.

b. Speed in the installation rate.

c. Less joints – easy to maintain cleanliness.

d. No of tile / stone requirement will be less in terms of numbers.

e. Versatile and stylish look - high-definition digital printing technology provides look of hardwood, natural stone, or some other architectural material in large format tile, etc.

As per some of the standards like, IS / ANSI / ISO / BS-EN defines the tile / stone as large format, if they have size of one side at least 400mm OR 400mm x 400mm OR 400 x 100mm OR 600 x 150mm. Some standards describe as per the weight of the tile/ stone i.e. more than 32Kg/Smtr. Some stone used at facade cladding which are of length 400mm / 600mm / with width of 100mm / 150mm with thickness of 15 to 30mm thick, were also considered as large format stones. But in market, tile of size 1.2Mtr X 1.2MTr vitrified tiles, 1.2Mtr X 2.4Mtr slim tiles and 1.2Mtr X 1.83Mtr stone of natural / artificial stones are easily available.

Something when comes with advantageous, dis-advantages will be there as another face, as follows:

1. Large tiles when needs to be installed, the substrate shall be prepared in level at tolerance of 3-6mm per 3Mtr length. If surface is undulated it needs to be re-surface or wet on wet system of installation to be followed which results in increase in the floor level.

2. Handling of the large tile / stone needs more man power and mess the job site.

3. Large tile / stones need more time to place in position and needs more effort to fix them 100% bonded.

4. Large stones, needs to be applied with epoxy mesh on it back to avoid cracking while transportation and installation. But this mesh installed with epoxy creates weak in bonding.

5. Substrate needs to be good, strong and shall have more than 1.5 MPa surface tensile strength.

6. Large format tile / stones shall be of non-porous material, if not they may increase the weight by absorption of water / dampness / moisture and may cause falling from the wall.

7. OH&S AND PUBLIC SAFETY shall be considered as important because of the size and load depending on where to be installed. Ex, at wall after 3Mtr height, use clamps. Do not install at against gravity situation. 
Some of the clamps available in the market are:

8. Large tile / stones of moisture sensitive are tends to fail by warp. So, they need special made adhesives.

9. Provision of providing tile / stone joints will be less which easily create more chances of lippage problem while installation and pop-up of tile / stone at later stages due to movement in the substrate.

Let us see how to adopt the best installation procedure for Large tile / stone as per their nature and categorization. Large tile / stone formats can be divided as follows:

1. Large format stones – Marbles / granites and other natural stones which are porous in nature and cut in to large size.

2. Large agglomerated format stones – Manufactured by the processing the marble / quartz stone + resin + hardeners. 
Many manufacturers of quartz tile recommend preconditioning of their tile before installation. They recommend storing the tiles for a given time period in the location where they will be installed so they become acclimated to temperature and humidity of the environment. Be sure to fully read the quartz tile manufacturer’s instructions before beginning the project and keep in mind that you may be required to precondition the tile for several days before installation.3. Thin large format tiles – Modern technology invented light weight, semi / fully vitrified lesser thick tiles.

The area of the large format tile / stone shall not be more than 1.2 Smtr. Stones which are porous in nature shall be treated with under tile / stone primer at all surface expect the top surface to avoid the wet patches, chemicals and efflorescence from the substrate which causes permanent bad patches in stone. Along with the under tile / stone primer, if we apply sealer on the top surface, natural and artificial stones will be protected from the moisture from the substrate and top which can causes the warping. Always maintain min 2mm spacing around large format tile / stone to accommodate the substrate movement.

Mesh is provided for the large format stones and slim tiles as they are weak in tension and may cracks while transportation and handling. But, mesh is also provided to small tiles and stones to unite them to form specific group of style / passion. Mesh will be pasted to the back of the tile with epoxy glue. This glue and the mesh shall be water resistant and shall not be of bio-degradable. Mesh should not cover the 25% of the tile or stone. To avoid these problems, some tile were placed with paper on the front Ex glass mosaics with paper fleece.

Adhesive selection for the installation is the very important in the installation of large format tile / stone.  Natural large format tiles shall be installed using high polymer modified cementitious non-slip adhesives. Large format tile / stone of artificial and natural stones which are not applied with epoxy mesh, requires highly polymer modified cementitious extended open time deformable adhesive. The same stone are installed with epoxy mesh, then use epoxy based adhesive. Thin large format tile requires, thin layer of epoxy adhesive or highly polymer modified cementitious extended open time high deformable with non-slip property adhesive.