Seal crack in concrete deck

[kfc510]

Ok, not my work, not my responsibility. But...

I am doing seismic work on a 1961 house in the east bay hills. The obviously imperfect (+/- 8'x50') front porch/deck/patio is a concrete slab over 1x sheathing.

There are two cracks running across the 8' dimension that have been allowing water to freely drain through to the crawl below. We are currently in the dry season, but some over-watering of planters above shows damp areas below, complete with mushrooms. Upon examination, there is evidence of repaired rot, and obvious signs of moisture intrusion. The porch will receive rain in the wet season.

There is remarkably little damage to the untreated fir joists, testament to the theory (in California, anyway) that if you don't trap the moisture you can literally let liquid water run through a house. (For some time, anyway, who knows when the cracks developed.)

Again, I am not hired to diagnose or inspect water problems. I am simply the guy in the crawl space doing a seismic retrofit. However, upon seeing this, I had to mention it to the HO.

Short of ripping the entire porch out and starting over, what are your collective thoughts?

Any (even half-assed) ideas about slowing the water intrusion? With the understanding that we are not trying to "fix" it for now? What would you do if it was your house?

Have at it!
kevin

[Ablesupe]

Re: Seal crack in concrete deck

If the cracks are reasonably equal distance apart I'd cut out an 8"-12" section of the concrete across the deck. Cut reglets in the sides of the concrete cut and pour back a minimally sloping base, then form a bitumen coated copper pan that slopes to o/s deck edge to sit on top of the sloped base and fits into the side kerfs. Water seal the reglets and pour back a concrete cap as an accent strip. Just short of the low end of the pan I'd install a weep hole type rope that daylights on the edge of the porch in two spots. I'd leave the joint between the new concrete and the existing low enough to receive a waterproof caulking that could be removed and replaced every few years

[kfc510]

Re: Seal crack in concrete deck

That's an interesting thought, thanks for the reply.

kevin

[calvert]

Re: Seal crack in concrete deck

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[NW Architect]

Re: Seal crack in concrete deck

With that surface, you'll never get the crack wide enough to seal.

I'd buy me a gallon or Bora-care solution and pour it slowly over the cracks so it seeps in. Same viscosity as water, will follow the same pathways and diminish any growies in there. Come back in a month. Spray a silane-siloxane waterproofing over the whole deck, with a little extra shot on the cracks. That will make everything more hydro-phobic.

Repeat every year

[kfc510]

Re: Seal crack in concrete deck

Spray a silane-siloxane waterproofing over the whole deck, with a little extra shot on the cracks. That will make everything more hydro-phobic.

Repeat every year

I've never tried concrete sealer to fill cracks. You think that would work? Even for a year?
kevin

[NW Architect]

Re: Seal crack in concrete deck

Its not going to fill the crack. Just makes everything the water contacts less prone to absorbing the water (and the borate makes it less prone to developing fungus)

[kfc510]

Re: Seal crack in concrete deck

Its not going to fill the crack. Just makes everything the water contacts less prone to absorbing the water (and the borate makes it less prone to developing fungus)

That would help with general porosity, then, but the problem areas are directly under the cracks where water has been freely flowing. It's possible a regular borate (or other) treatment would fend off decay somewhat, but I think some effort at sealing those cracks needs to be made.

That or rip the whole thing off and start over, of course.

[TWhite]

Re: Seal crack in concrete deck

I prefer the start over and do it right idea.

[kfc510]

Re: Seal crack in concrete deck

I prefer the start over and do it right idea.

Yeah, so do I. and that's undoubtedly what has to happen at some point.

But these folks just bought this place. When I first mentioned the wet areas, they didn't seem to recall any pre-sale inspection item (inspections are a joke in this market). I am hired to do unrelated seismic work, not inspection.

I really don't want to throw the bucket of cold water on them and say "Oh, btw, now you need me to do 15k of work over here too."

I will mention that is probably the only real solution, but I'd like to offer some short term band-aids as options too.

[TWhite]

Re: Seal crack in concrete deck

Maybe some of that paint advertised for old decks might fill the cracks?

[kfc510]

Re: Seal crack in concrete deck

Maybe some of that paint advertised for old decks might fill the cracks?

Good thought. I also thought about a Gaco type sealer product. I've used those on exposed ply with some decent results.

Either way, something runny enough to get in there, but then will set up as a flexible gel-like material?
http://www.gacoretail.com/gacodeck.html

[Ted S.]

Re: Seal crack in concrete deck

I'd recommend Bondo with a good primer.

[kfc510]

Re: Seal crack in concrete deck

I'd recommend Bondo with a good primer.

LOL, Ted. You got me.

[Ted S.]

Re: Seal crack in concrete deck

You're a good sport, Kevin.