jigwig

Is anchoring always done at the bottom?

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So for instance, you can have a free standing wood post anchored at the bottom to concrete. But what if you have a post attached in all directions to something above it, very securely there, and it was wedged in between that and a concrete floor to begin with (a tight fit). Is it going anywhere? Or say you connected a free standing table to four walls around it from its top. Is it anchored then, or is anything else considered bracing, even if what it is connected to is anchored to the ground?

I was reading something about anchors, as far as what they do. "Wedge anchors secure themselves using a mechanical wedging effect at the end of the fastener". So to me that sounds similar in essence. If a post is wedged by itself, it seems comparable mechanically, in that anchoring is being qualified as wedging, in the case of fasteners that do the anchoring as such. Of course those would be stronger wedges in and of themselves. But relative to a post anchored only at the bottom with those, and nothing holding it above, versus the flipside, with the post resisting movement both by fitting between the floor and points of attachment above, I wonder if this would be like an upside down anchor, or if anchoring is distributed (if what the post connects to above is anchored to the floor).

 

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As a practical matter, I was also reading about how concrete has to be x-rayed or radared to reliably determine if adding anchors would interfere with rebar in a floor, or electrical lines running under it. So as far as retrofitting wood there, I'm considering the necessity of hacking into concrete in addition to reinforcing the wood itself. Not really as a matter of building code, as improvements would be above that to begin with, and obviously if people in natural disaster areas have nothing but a foundation left after the fact, it doesn't seem to work all that well (floor anchoring, that is—to the extent that everything touching a floor would have to be anchored there to be considered sturdy). In other words, can wood be connected together at the top without anchoring every piece individually to the floor, and still be considered as anchored all together, if any piece that isn't anchored that way is surrounded by pieces that are? I used the free standing table as a simple example of this concept.

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You are reading beyond what most practical situations require. Having said that, you won’t get good opinions without specifics. The size and weight of the piece, as well as the nature of what braces it makes a big difference. Post a sketch of what you envision. 

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The concrete being x-ray'd requirement is usually for multiple story buildings. A lot of them have cables under tension in the slab that are structural. They shoot nails through the metal floor track for lightweight steel framing without needing to X-ray the slab. But if a plumber or electrician needs to bore a hole in a high rise floor slab it must be xrayed. A hole for a concrete anchor in a grade level slab in residential housing might not need it. 

Can you be more specific what and where in the world you are trying to do something ? How old is the building ? What floor are you on ? Commercial or residential ?  Wood pole into concrete for what reason ?

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Might not is the thing I wouldn't know until I did or didn't hit something trying to do drill an anchor hole.  I'm talking about extra vertical supports with 4x4 lumber. It seems like it could be a general concept though, to do with the properties of wood, you know? Like anchoring itself is a general concept. But does it have only one dimension...

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This discussion is bordering on philosophical! Taking your vague example of a 4x4 as an additional building support, I think the idea of anchoring or attaching at top and bottom is to eliminate the possibility of the structural support being easily removed by accident. I would not depend solely on the wedging of the 4x4 between ceiling and floor in that case.

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It only matters in certain situations. Californian is very different from  Georgia. A Residential home on a slab or a basement floor is very different from the 10th floor of a high rise. 

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2 minutes ago, jigwig said:

It is a hypothetical question in essence, thanks. Has to do with wood, that's all I know.

In that case, a wooden structural member would best be fully attached, as wood moves with changes in its environment. Wedging of the wood alone can loosen ove time.

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14 minutes ago, wtnhighlander said:

In that case, a wooden structural member would best be fully attached, as wood moves with changes in its environment. Wedging of the wood alone can loosen ove time.

So at worst, if the wood contracted with environmental changes and was suspended 1/16th inch off the floor by its secure attachment above, instead of being wedged at the bottom otherwise, then it would merely serve its purpose after making contact again as it was compressed from above. Or would there be other consequenses in this case? I'm not trying to argue that additional floor anchoring isn't best, except if trying to do so could cause more problems than a piece of wood changing its size occasionally.

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We would like to help but you would be much better with a sketch or specifics. Please answer a few of the questions already posed to you so we can tailor the appropriate response. There are real people here ready to answer if possible.

 

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Thanks, I think the title describes the topic well enough, if you're intersted. "Always", meaning would you consider a piece of wood to be anchored only if that was done at the bottom? Or can you think of any situation where the opposite would seem sufficient, and connecting it all around  would be excessive? Once again, a table is not typically anchored either way. So if it was "anchored" from above, so to speak, would you think it was missing something...would this be an improvement to its anchoring in genreral, or only if it was attached to the floor? This is a specific example, all be it hypothetical (for comparison—perhaps a rule of thumb, if there is one about what constitutes anchoring). I'm interested in your opinions, other than as to what my topic was about to begin with, but you can talk about that too, if it seems interesting (I don't mind, just saying).

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Reminds me of bureaucrats and lawyers that ignore anything that doesn't support their assumptions and refuse to answer any questions.

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Looks like examples of overhead anchoring are given for scaffolding or ladders, which would rely on the rest of the structure having ground anchoring in addition to what they are hooked up to, as with decks or overhanging roofs being suspended from one end of a building. It would be more unusual to do this at ground level, although I guess it's much less extreme than those situations, especially if the boards are relatively short.

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You referenced free standing in the OP, but without height or connectivity. I think without any more specific question, this thread needs to be scrubbed. There are entire tables in manuals that deal with depth into concrete, fastener thickness and strength, etc. Thinking you are asking enough, while those of us builders say we need more is just plain rude. I also question language choices. You may feel you are being clear, but the posts read back a bit like Google translate. Be patient and throw us a bone, we like to help. But, slow down and try to clarify because the field is too large for blanket hypotheticals. 

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I don't know about that, if you don't happen to have reasons for or against anchoring a particular way, without a blueprint from me, that wasn't what I asked. I just said for instance. If you want there to be more on my mind, I'd be happy to hear it. Although, if this is far and beyond a general concept, I think that sounds ironic.

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I am hesitant to discuss this topic without specifics because as tom king said "it depends" but mainly because without the specifics I would not want to give advice on this because in certain instances the result could be damaging to structures and or human lives.

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How do you know this? Just curious... I mean that sounds like a general concept (so I have no idea what you're talking about).

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I think it depends on which controlled substance has been ingested. I think someone is having some fun with us.

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