Lipping is not something most of us have heard of, but you have probably noticed it before without knowing the correct name or why it happens. Lipping, or lippage, is the term used to describe the difference in height of the installed tiles. This can be particularly unsightly if measures are not taken to avoid it, and can even cause damage to the tiles or become a tripping hazard.
How does lipping occur? The main cause is actually bowed tiles – most tiles will have a slight bend thanks to the way they are produced. The heating and cooling processes cause the edges of the tiles to bend slightly, and no matter how much care is taken this will happen to most tiles. On smaller and square tiles this is less noticeable, however this becomes more obvious in larger oblong and plank tiles.
There are standards throughout Europe for bowing; the centre curvature for porcelain B1 is +/- 0.5% of the diagonal size and for porous tiles (ceramic, stone, slate, etc.) B111 it is +0.5%/-0.3% of the diagonal size. This means that on a large format 900x300mm tile the bowing could amount to 4.74mm and still conform to European standards. If this tile was laid in a broken bond pattern that would result in lipping of nearly 5mm and look very unsightly. The larger the joint, the less obvious the lipping will be. However with more large format tiles being finished with a rectified edge (a very precise square profiled ground edge) and a narrow joint the problem becomes more apparent.
Tips for Avoiding Lipping
- Make sure the sub-floor is level and even before tiling – you can use a self-levelling compound.
- Before fixing lay the tiles out on a flat surface and butt joint in the pattern you will be using.
- Use the right joint thickness, a narrow gap will accentuate any difference between the tiles.
- When installing use a levelling clip system to ensure you are creating a level tiled surface.
- Check your lighting, some extra bright or incorrectly positioned lights can make even the slightest irregularities stand out.
- If lipping looks excessive try laying the tiles out in a 1/4 or 1/3 broken bond pattern, or use a square bond.
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