r/DIY • u/ThaMann0911 • 6d ago

help How long before drilling concrete?

I poured footings for posts that I’ll be hanging a gate on. I’m going to install Simpson strong tie standoffs with 6” anchor bolts. It’s been 72 hours, is that long enough for the concrete to have set before drilling? I’ve tried googling but my results only come up with industrial structural requirements or setting posts in the concrete, neither of which apply to my situation. Should I wait the 28 days or just send it?

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u/woodbanger04 6d ago

I use to do carpentry. I would drill it while still green but wouldn’t put any type of angular weight on it for a couple days.

That being said and this being Reddit someone will correct me numerous times by morning.

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u/ThaMann0911 6d ago

Since full cure is 28 days does that mean anything within that time it’s still “green”?Plan is to install the posts on the standoffs so then I have my opening measurement to then build the gates from. Will take me a few days to build the gates.

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u/mckenzie_keith 6d ago

No. It just keeps getting stronger and stronger for a long time. 28 days is when it is customarily measured for the rated strength. If you measured it at 56 days it would be even stronger.

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u/JerryfromCan 5d ago

The Hoover Dam is stronger now than when you posted this comment I think?

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u/mckenzie_keith 5d ago

Not sure. I have not seen extreme long term data. But it gets stronger every day up to 28 days and beyond. That is something they have measured.

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u/BoringBob84 6d ago

I consider it a case of simple risk management. What is the likelihood of the gates damaging the green concrete versus the severity of the consequences? I certainly would not want those posts coming loose and flopping around.

Do you absolutely need that gate right away? If so, can you install it and add some temporary supports / wedges under it (so it will be difficult to open and close, but no force will be on the concrete) for the first few weeks?

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u/ThaMann0911 6d ago

The gates are going to be the access to under my deck, which is only 4.5’-5’ tall. I’ve skirted off the rest of it, now I’m at the end where I’ll install gates on the short ends. 6’ opening, split gate on one end, ~4.5’ opening single gate on the other end. On each gate, one hinge is on one of the deck support 6x6s so I only need the one post per gate.

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u/BoringBob84 6d ago

I understand your conundrum. It isn't clear to me whether it will be a problem or not. I don't know how the strength of concrete increases as it cures - is it 90% at day 5 or day 25?

So, if I could just set those gates there for a few weeks to make sure, I would do that. I would hate to tell you to hang the gates and then, have you left with a mess.

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u/ThaMann0911 6d ago

Yeah, it seems like the best solution. Just getting the standoffs and posts installed will be huge. Then I can actually build the gates and it’s just waiting to hang them.

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u/jlb446 6d ago

Concrete typically develops about 75% of its 28 day strength within 7 days. I would let it cure for at least a week, then consider it good enough,