There is a curved about 2.5 inch crack on top of second step that I patched with A+B Epoxy Putty. However, two weeks later, hardened epoxy start pealing and coming off the place I patched and crack is now open and leaks again. I think the reason is that the step is not firm and bends a little under press when somebody steps on it, it may be because some of the dirt (or whatever it is) was washed out from underneath of the step so hardened epoxy finally cracked as well and came off. Do you think Flexible Sealer will help to resolve this problem or I really need to fill washed out space first and then seal the crack? Crack is really small and I’m not sure what is the best way to fill the gap and make the step steadier. Thanks for any suggestions or information.

I have used the flexible sealer to get to the end of the season on small cracks as a temporary fix, on larger cracks i have sealed the crack with the butyl rubber conduit sealer and then covered over the butlyl with a layer of flex sealer. After the season ends I then lower the water for a fiberglass repair with fiberglass sheets and gel coat from a boat store
Bruce
poolrepairdiver.com

To fix the problem right.....you'll have to "flush" a vermiculite and portland cement mixture under the stairs to fill the void. To do this.....I drill two 1" holes in the lip on each side of the stairs.....you may then have to take a hilti hammer and break any concrete under the hole from when the deck was poured. Once the concrete is removed.....you should be able to pour the mixture under the stairs. Take a 100 lb. empty chlorine bucket....use a hole saw to drill a hole in the bottom....and then screw in a standard aboveground fitting in the bucket. Put the fitting into the hole so the bucket acts as a funnel.......mix up you mixture on the wet side so that it will flow easily.....and pour it under the stairs. Use a rubber hammer the tap the steps as you pour to help the mixture spread around. You should see the "spring" in each step go away as the void is filled. Once finished....use white plastic caps to cover up the holes.....then use Anderson's epoxy or flexible sealer to repair the crack. Hope this helps.

Talk with Lance.Used prototype foam with great success.Repaired quarter inch crack width of bottom step and heighth of riser up to secound step using Jake gun.Void was one inch under bottom step with no backfill under secound step.Foam filled void completely. covered crack with plast-aid.Two weeks and no leaks.

We have been using builder's expansion foam to fill voids under steps for 2-3 years with good results.

I've been using a product that's at beauty supply stores for far longer than plast-aid has been around. It's the stuff they use for building finger nails. Just like plast-aid it's a powder and liquid mixed together. I like using the small glass, thimble sized cup for mixing in. They also have some "all plastic droppers" for dispensing the liquid into the powder. It's also a good idea to have some bamboo skewers to mix with. I can't believe people bond this stuff to their finger nails.... It smells harsh.
hap