Prep for Swimming Pools & Hot Tubs

Here’s everything you need to know about preparing Swimming Pool and Hot Tub surfaces for microcement:

MicroRock Base is used for Swimming Pools and Hot Tubs, to ensure ground water won’t affect the microcement system. It is a very strong epoxy based products so has some special requirements:

Strength of Substrate
MicroRock can only be installed on a substrate with a minimum compressive strength of 25N/mm2 (aka MPa) and a Tensile strength of 1.5N/mm2 (aka MPa)

Completely Flat
Surfaces must be completely flat before microcement is applied. It will follow the contours of the substrate and can’t be used to fill large voids. Blocks and bricks will need to be rendered with concrete before microcement is applied.

Generally, the following surfaces meet the necessary critera, but please check with the manufaturer to be sure:

CONCRETE

SCREEDS

CONCRETE RENDER

Cured to less then 10% moisture content
If there is still moisture in the substrate, the microcement could blister or de-laminate as moisture is trapped under the surface. Surfaces that aren’t fully cured are also more likely to crack as they do so whilst curing. The moisture content can be tested with a moisture meter or by checking with the manufacture of the screed. The drying time will depend on the depth & the type of product used.

Repair cracks under 3mm wide
Use a 5” grinder to open up the crack (take care not to cut into any underfloor heating), hoover out any dust then mix Epoxy with Epoxy Hardener (Ratio 5:2) and pour into the crack. Leave to cure fully this will take for at least 12 hours. It may need topping up depending on how deep the crack is.

Repair cracks over 3mm wide
Use a 5” grinder to open up the crack and grind approx 100mm “stitches” horizontally across the length of the crack around 40mm apart (take care not to cut into any underfloor heating), hoover out any dust then insert steel helical stitching bars into the stitches. Mix Epoxy with Epoxy Hardener (Ratio 5:2) and pour into the crack. Leave to cure fully this will take for at least 12 hours. It may need topping up depending on how deep the crack is.

Do not Prime the Surface
It is best to go directly onto the surface with MicroRock Base, no primer or mesh. However if there are a lot of cracks &/or joins in the substrate. It may be appropriate to use epoxy, mesh & sand blind.

Epoxy, Mesh & Sand Blind
This is the more advanced priming process, which we highly recommend for floors with joins

The products required to Epoxy, Mesh & Sand Blind are included in the Floor Strengthening Kit or by choosing High Performance Primer when you buy a kit from Relentless Microcement.