QUESTION

Substrate and Movement Joints - I'm installing 18"x18" tile to a very large area of floor, the floor starts over a heated basement,continues over a unheated crawl space and finishes over a concrete slab. what would the correct method in installing this tile over different areas, would i need to install expansion joints, if so, what type?

ANSWER

ANSWER - If I understand your question, you are saying that you are installing 18x18 ceramic tiles over 3 floor areas.  I assume one is a concrete slab, and the other two are wood sub-floors with one of the lower areas heated and one not.

First keep in mind that expansion joints (movement joints) should be placed in the floor around all perimeters, transition of planes, every 24 feet in the floor areas in both directions, and continued up from any existing joints in the slab.

Second keep in mind that the floor can not exceed a deflection of L/360 for ceramic tile and L/720 for natural stone.

I would treat the 3 areas as three separate installations separated by full movement joints down to the sub-floor.  You can build up each floor to be level with each other or you can step down or up.  The ideal system is a full wire reinforced mortar bed that gives you best system and most flexibility other than if there are height limitations.  Next best is to apply a cementitious backer unit, an uncoupling system or self-leveling underlayment to flatten the surfaces and give a good surface to bond to.

Movement joints should continue up from slab joints and be filled with a backer-rod and an appropriate sealant with a shore hardness of 35 or greater.

Good Luck!