LATICRETE 3701 vs a Basic Sand-Mix Mortar Bed: Why Your Shower Floor Mud Matters

The short answer: a shower floor bed is a stiff, packed mortar. A basic bagged sand mix can work when it’s mixed and packed right, but get the water or the packing wrong and it can stay crumbly and weak under the tile. LATICRETE 3701 Fortified Mortar Bed is polymer-fortified and premixed: you just add water.

What “dry pack” should be

Shower floor mud is mixed much drier than concrete: damp enough to hold together when you squeeze a handful, not so wet it slumps. It’s then packed hard and screeded to slope. The packing is what makes it solid.

Mixed right vs mixed wrong

We don’t publish mix ratios here: follow the bag. Ratios for site-blended sand and cement vary by product and standard. I DON’T KNOW the right ratio for a mix I haven’t seen.

The numbers: 3701 vs a basic sand mix

From LATICRETE’s current North American 3701 data sheet (DS-100-1026). A basic bagged sand mix usually doesn’t publish these tile-bed numbers, so there’s nothing to compare against.

Why we use LATICRETE 3701

From the same data sheet:

• Polymer fortified: no separate latex additive needed.
• Premixed: no job-site blending of powders, so every batch is the same.
• Approved for bonded and unbonded thick-bed work, wet and dry areas.
• Can be pitched down to a feather edge when bonded with a 254 Platinum slurry bond coat.

Mike’s method

• Always a custom-sloped mortar bed, never a foam pre-slope.
• 2x2 welded wire mesh in the floor bed, at mid-depth.
• Rebar only in the curb, not the floor.
• Over wood: slip sheet, two lifts, 2 inches minimum, the way LATICRETE describes an unbonded bed.

Ahh ahh ahh! Beware of crumbly floor mud. A basic bagged sand mix that’s mixed too dry or too wet can crumble under the tile. We use LATICRETE 3701 Fortified Mortar Bed, mixed right. Why it matters. Best way? Do your research and hire a pro.

Basic sand mix: when it’s fine

A basic sand mix isn’t a bad product. Plenty of good showers sit on one. The risk is the mixing and packing. If you use one, follow the bag exactly and pack it hard.

Frequently asked questions

Why is my shower floor mortar crumbling?

Usually it was mixed too dry, not packed hard enough, or not cured before the next layer.

What is LATICRETE 3701?

A polymer-fortified, premixed thick-bed mortar from LATICRETE with high flexural strength (1,100 to 1,200 psi at 28 days per its data sheet). You add water only.

Can I use regular sand mix for a shower pan?

Many showers do. Mix it to the bag’s instructions, pack it firm and let it cure before waterproofing.

How thick should a shower mortar bed be?

For an unbonded bed over wood, LATICRETE describes 2 inches minimum with wire mesh at mid-depth.

Every custom bathroom renovation we build starts with a floor bed like this.

By Mike Bourdages, Burlington Tile. Last reviewed Mike to confirm review date.