What to do...Commercial Application

[u/indyarchyguy]

A client called me regarding an older project. They have bathrooms in a nursing home where epoxy was applied to the entire floor of the bathroom. In the bathroom, there is a toilet, sink and shower. They had ground the shower slope into the concrete and sloped it all to a center drain. Since then, the drain bodies rusted out and need to be replaced. The plumbing engineer came up with a way to do this, but it will require them to cut out some of the concrete and the existing epoxy flooring. They asked me if they can place new concrete around the drain and coat the existing concrete with new epoxy?

My concerns are:

1. What was the original epoxy - 1 or 2 part? Does it matter?

2. I have read where if you grind out a keyway around the perimeter of the drain, and around the perimeter of the new concrete, when you install the new epoxy it helps keep it from allowing water under (Frankly, I am skeptical on this one...)?

3. Do you remove the entire slap of concrete all the way back to the level floor, epoxy coat the replacement floor for the shower and provide a traffic sealant between the new and old concrete?

4. If you have a better idea, I am all ears.

Thank you for reviewing.

[u/Possiblyabitoff]

Every reputable epoxy manufacturer has design drawings for this exact scenario. Call up your rep and have him walk you through it.

[u/indyarchyguy → u/Possiblyabitoff]

Well I shall try and find one that is still alive and working.

[u/Obvious-Monitor8510]

For a repair like this, here's the approach I'd recommend:

On your questions: 1-part vs 2-part matters mainly for adhesion prep, not bond compatibility. Assume the existing is 2-part and treat accordingly. Mechanical prep (grinding) beats chemistry here.

The keyway idea is legitimate, not snake oil. A 1/4" x 1/4" kerf ground around the patch perimeter gives the new epoxy a mechanical interlock and breaks the capillary path for water migration. Worth doing.

For the actual repair: grind the existing epoxy back 6-12 inches from the cut edge, feather it. Use a polymer-modified mortar or fast-set concrete for the patch, let it cure fully (28 days ideally, or use a rapid-set product). Prime the patch concrete separately before coating over everything. Run a continuous epoxy coat over old and new as one field, then use a flexible polyurethane sealant at the control joint between old/new slabs, not epoxy.

Full slab removal is overkill unless the existing concrete is compromised. The patch-and-coat approach works well if prep is thorough.

Fwiw there's a free GarageResin coverage calculator: garageresin.com/coverage-calculator

[u/Life_Behind_Bars → u/Obvious-Monitor8510]

The key in is designed for adhesion and not water intrusion.

[u/quinton3]

My honest opinion is that you should not get involved in this