When I answer questions on my site I am always telling people to backbutter their tile. It has recently been brought to my attention that normal people (the ones who don’t stand in showers all day) have no idea what that means.
Backbuttering tile simply means spreading a flat layer of thinset onto the back of the tile before installing it on your wall or floor or whatever.
First you have to ‘comb’ the thinset onto the substrate – that means it is spread with the notched side of the trowel leaving little ridges. It should look like that first photo there on the right with the ridges all combed in one direction. This allows any air to escape from beneath your tile more easily.
Then, before you install each tile, you need to spread thinset onto the backside of the tile with the flat edge of your trowel – the one without notches. This accomplishes a couple of things:
- It forces thinset into the body of the tile. It completely fills all the little open pores in the back of the tile. This allows the crystals of the cement portion of your thinset to grow more deeply into the body of the tile, leading to a stronger, more durable bond to your substrate.
- It gives the back of the tile a 100% bonding surface for the thinset on your substrate. Rather than having areas on the back of your tile which may remain open or unbonded because the thinset cannot fully bond to them, it covers the entire tile with a flat, bondable surface.
In my photos I am installing a travertine tile, which is a porous natural stone. This will exhibit the need for Backbuttering since you can actually see the open pores in the back of the tile. The same applies to porcelain or ceramic, or any other type of tile as well, just on a more microscopic level.
I am also using a tool called the back butter buddy. It’s that turquoise frisbee looking thing (although you may be able to get it in designer colors – I’ll have to ask Phil…). It’s simply a turntable of sorts that you stack tile onto so you can spin it around to spread the thinset. It makes things a lot easier with larger format tiles.
All you need to do is flip your tile over so the backside is up, throw a glob of thinset (that is a standard industry measurement – a glob…) onto the tile and spread it out, forcing it into the body of the tile. The purpose is to force thinset into the tile, so you want to apply a fair amount of pressure as you’re doing this.
The least messy way is to start with the glob in the center of the tile and pull it towards the outside edge. Always starting with the entire blade of the trowel on the tile. If you start with part of the trowel off the edge and pull it toward the tile you’ll end up with a nice bead of thinset along the vertical edge of your tile. It’s difficult to explain – until you do it once. Then you’ll know exactly what I’m typing about.
And it’ll piss you off. And you’ll have to flip the tile, clean it off, wipe it down, your dog may burst into flames…it’s a whole thing. So try not to do that.
Once it’s evenly coated you can be assured you have a 100% bondable surface on the back of your tile rather than randomly flush surfaces where thinset may or may not bond.
Backbuttering is necessary. With any tile 12 inches square or larger you need to backbutter your tile to ensure proper coverage. If you do not the thinset may not bond properly to your tile.
The photo to the right is a tile I removed from an installation that began having issues – not backbuttering led to a poor bond. While that was not the only issue here, it definitely contributed to the overall failure.
In both of those photos you can see that there is VERY little, if any, thinset actually bonded to the back of the tile. Backbuttering is necessary.
Backbuttering is only one step in the process of a proper tile installation. Every step that is done correctly increases the chances of a successful, long-lasting and durable installation. Every step you skip increases the chances of a failure. So take your time, utilize the proper technique and pay attention to detail. If you do that you and your dog will both live a long, flame-free existence.