Module 9 of 10 200m 200 min 10 exam Qs 10 exam questions covered
Mortar Bed Installation
Mud beds, dry pack mortar, float coats, metal lath reinforcement, thin-bed vs medium-bed methods.
- Construct a mortar bed using dry pack technique with proper reinforcement
- Apply a float coat for a smooth, flat tile substrate
- Compare thin-bed, medium-bed, and mortar bed installation methods
- Install in-floor heating systems under tile
Lesson 1
Mortar Bed Construction
The Traditional Mud Bed
A mortar bed (mud bed or mud job) is a layer of sand-cement mortar that creates a flat, stable substrate for tile. It is the most versatile method because it can be shaped to any slope or level.
20-38 mm
Standard Floor Bed Thickness (3/4" - 1-1/2")
4:1
Sand to Cement Mix Ratio
Metal Lath
Reinforcement Required on Walls
Mortar Bed Components
- Sand - clean, sharp sand (not play sand or beach sand)
- Portland cement - standard Type I or II portland cement
- Water - just enough to achieve a "dry pack" consistency
- Metal lath - expanded metal mesh for reinforcement (required on walls, optional on floors over membranes)
Floor Mortar Bed Procedure
- Install vapor barrier or membrane if required
- Set screeds (guide strips) at the desired finished height
- Mix mortar to dry pack consistency (holds shape when squeezed, crumbles slightly)
- Pack mortar between screeds, compact firmly
- Screed flat using a straightedge riding on the guide strips
- Float smooth with a flat steel or wood trowel
Dry Pack Test
Squeeze a handful of mortar. It should hold its shape but crumble slightly when poked. Too wet and it sags; too dry and it will not compact properly. Think of damp sand for a sandcastle.
Key Takeaway
Mortar beds use dry pack mortar (4:1 sand to cement ratio) that holds its shape when squeezed. Standard floor bed thickness is 20-38 mm. Wall mortar beds require metal lath reinforcement. The mortar must be compacted firmly and screeded flat.