Rain ruined my patio!
October 7, 2009 5:58 PM   Subscribe

DIY-Disaster Filter: I sealed my new (expensive) concrete patio with water based sealant. Followed the directions by cleaning it the day prior and waiting 24 hours for it to dry completely. Just as I was finishing my first coat it started to rain unexpectedly. Help me fix it!

I stopped applying any sealant once it started to rain and hoped it would be dry enough (it was dry to the touch) to be 'ok'. Well, two days later, I cleaned it and am noticing that the water is still seeping through in areas and making it dark (indicating absorption and a bad seal). I also have one or two areas that appear to have moisture trapped under the sealant as they are dark and splotchy (near the downspout where the water was running just after it was sealed).

Is there anything I can do to make this better? I think it needs a second coat of sealant but am unsure of how to proceed now that the first coat has failed. Am I destined to stripping it and starting over? If so, what is the best recommendation for that procedure?

Here are some photos of it right after I wet it down:


The stamp color was a light tan and a cream colored release (the cream in the photo is the release color, not over-application of sealant).
posted by shew to Home & Garden (5 answers total)
Given the amount of effort it would take to strip your current sealer coat, I'd give it a few more days to dry, in sunshine, if the weather permits. Sun warmth and UV radiation may still cure your sealer a bit more. Also, your results are going to be influenced by how "new" your patio really is; most residential concrete mixes contain excess water (called "water of hydration") to aid the curing process, and keep slabs from having to be kept wet by the homeowner, as early curing proceeds. And most mixes for outside patios, walkways, and slabs also contain crack-resistance additives, that entrain air, inhibit rusting of any rebar reinforcement, and slow development of gypsum crystals, but that also make the mix a bit slower to release water of hydration. So, normally, you want an outdoor patio slab completely cured for a few weeks, and then allowed to thoroughly dry, before putting on any kind of external sealer.

If the project still looks bad, and is obviously letting surface water through the sealer in a couple of weeks of additional drying, I think you're going to have to mechanically abrade the surface down to fresh concrete, acid etch the fresh surface, and re-seal it, again. But do be sure your slab is properly cured, and that you have above minimum temperature conditions to seal it, then.
posted by paulsc at 8:46 PM on October 7, 2009

Response by poster: To clarify, the patio was poured 48 days ago. I waited the recommended days for curing before sealing...
posted by shew at 8:56 PM on October 7, 2009

48 days isn't very old, particularly if your patio is patially shaded by the house during the day, or if you've had any rain in the interim, and didn't cover the patio and surrounding ground with a tarp, to keep the site dry. It may be the minimum recommendation, but 90 days is usually a more reasonable length of time to wait before sealing new outdoor concrete, in most temperate climates.

At any rate, you've applied this sealer, now. I'd really wait for a couple more weeks, hope you have some warm days, and see what happens. If the appearance situation improves with time, I might even put another top coat of sealer on while the weather is still warm, before going to all the work of stripping the existing sealer. If the weather turns cold on you in the meantime, I'd wait until spring to strip and reseal, rather than do it in cold or wet fall weather.
posted by paulsc at 9:24 PM on October 7, 2009

What kind of sealer was it? For an exposed slab like that, you probably want a silane/siloxane sealer, as opposed to a membrane type sealer. Silane sealants allow moisture to escape the slab, but shed liquid water.
posted by electroboy at 6:37 AM on October 8, 2009

Have you given the manufacturer of the sealant a call? I've found customer support lines for products like this to be helpful and knowledgeable.
posted by Mitheral at 7:07 AM on October 8, 2009

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