Repairing rusted steel posts in crawlspace

what_nowApril 6, 2014

The house I am buying was built in 2000 in the mid south (non coastal). Its built on carwlspace and all of the steel supports are rusting at the bottom. This is due to the design of the crawl. The builder put trenches in to drain any water out (lot slopes front to back). Sadly, the steel posts sit in the trenches. The general inspector noted "Monitor Condition". There are no cracks or settling evident.

However, I had a structural engineer out for some remodeling plans and had him look. He said its an issue, not huge, but should be repaired.

He suggested drilling a hole through the steel high above the water line and putting a bolt through and then pouring concrete around. Or cutting the steel post high, pouring concrete footer and then bolting the post to concrete.

Do these sound like good ways to deal with this? I was leaning towards the first option of drilling a hole through and adding a bolt and concrete around. And any suggestion on how this should be done? What type concrete and bolts to use? How much concrete and do I make a form for each first? I have done a lot of diy projects and this seems like it should be straight forward but its not something I am familiar with.

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You say the posts are sitting in the trenches. Can you pour the concrete blocks at the base of the posts without blocking the trenches?

If you're going this route, I suggest putting a water stop in the concrete around the post to keep the water in the trench from getting under the new block at the cold joint and then at the steel again.

Here is a link that might be useful: waterstop info

    Bookmark   April 7, 2014 at 1:58PM
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I'd have to see pictures and drawings before commenting.

    Bookmark   April 7, 2014 at 8:22PM
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I have no drawings :-(
I can get a pic when I am back over there Friday.

    Bookmark   April 7, 2014 at 8:48PM
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I've not built one without them.
Are there any perimeter foundations supporting the exterior walls?

    Bookmark   April 7, 2014 at 9:57PM
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Im not too familar with how crawl spaces are constructed as I have previously lived where basements were the norm. I am in a larger metro area that has adopted building codes (not sure which version in 2000). From what I can see, there is concrete along perimeter that appears to be poured concrete. The crawl is close to 6 feet tall in some areas. Both the structural engineer and a contractor I have spoke with have mentioned the existing concrete footings. I am setting a meeting up with the engineer, contractor and myself to discuss the plan. I did have a basement co out who suggested just replacing all 25 steel posts with galvanized steel posts. The engineer thinks thats overkill and doesnt really solve the entire issue that the pists arent elevated out of the drainage trenches.

    Bookmark   April 7, 2014 at 10:06PM
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The hole and bolt idea is to give the concrete something to hold on to. There may be a possibility of the steel shaft sliding in its new concrete housing. ItâÂÂs just for insurance; you could do more than one bolt, fâÂÂrintance. DonâÂÂt even need a nut.

There are a thousand ways to do this. Here is one just to get the idea across. You take a cardboard tube made for pouring concrete in. Cut it as long as you dare but short enough so that it can sit around the steel post and on the ground but be long enough to enclose that anti-slip bolt or two and for you to be able to put concrete in via the top. Most likely with a garden trowel one scoop at a time.

You slit the tube and pry it open to get it around the post. Tape the slit shut with lots of duct tape and then reinforce that with some wire or hefty cable tie wraps. If you're doing this after you secure a footer, make sure the tube bottom is a close fit to the footer to minimize squeeze out. Smack the tube a few times with a smacker to try and minimize voids (bubbles) in the concrete.

When set, remove the form and move over to the next post to repair.

    Bookmark   April 7, 2014 at 10:22PM
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So, assuming there are perimeter stem wall foundations, how does the water get underneath, in sufficient volume that drainage trenches are necessary?

    Bookmark   April 7, 2014 at 10:22PM
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If you have the steel posts just sitting on dirt or such, you need to spread the load out with almost anything that can be called a footer, such as a fat wide puddle of concrete, a couple of cap blocks or solid 8 X 16 blocks, chunks of broken-up sidewalk, and so on.

    Bookmark   April 7, 2014 at 10:45PM
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How does water get in? My understanding is crawl spaces as typically designed here on not meant to be water tight like a typical basement. The lot slopes front to back and is in a hilly neighborhood. Certainly the lack of gutter downspout extensions directing water away doesnt help. That will be immediately fixed. We have had pretty good amount of rain the last time I was over and there was very little water in the space. It appears that the houses were designed this way. Not the way I would have chosen.

    Bookmark   April 7, 2014 at 10:48PM
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I believe there to be concrete footings under each post. I just havent seen it personally. In several areas there is a concrete pad that I can see. The others are under black plastic - I just need to get access to verify.

    Bookmark   April 7, 2014 at 10:51PM
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"My understanding is crawl spaces as typically designed here on not meant to be water tight"

Whole typical concrete mixes for poured in place foundations use common cement and are not considered "water proof", unless cracked and broken, are considered water resistant.
"Generally" in the condition you have described require the lot drainage to be amended to direct the flow away from the dwelling.

While plastic is often used where water intrusion is evident. The plastic is affixed to the posts and the joints are lapped ad sealed to form a monolithic membrane with fans to exhaust the moisture..

    Bookmark   April 7, 2014 at 11:49PM
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I will get some pics on Friday. The plastic is just the typical black plastic over the dirt. Its what I have seen here in every house I have looked at. I dont believe its an attempt to water proof it at all. Definitly no fans. Just the crawl space vents.

    Bookmark   April 8, 2014 at 12:02AM
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Because it, for your area, is systemic, does not address the fact that wet wood rots, besides attracting several different infestation, in addition to the issues you are facing.

So, why not eliminate the cause, as well as the effect.

Were I you, the first step would be to effectively dorrect the lot drainage to the sides of the dwelling and away from any possibility of intrusion.

Next would be to determine the extent of the deterioration, as evidenced by the rusting, by removing the rust with a wire brush, emery cloth or mechanical sander.

It may be just surface and can be addressed with a rust inhibiting primer.

I would not drill and weaken the posts and simply insert a bolt, unless it is welded.

    Bookmark   April 8, 2014 at 10:31AM
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