I have had the same discussion a couple of times lately, expressed my opinion and then qualified that opinion with a description of the breadth of my ignorance.
The discussion subject is: what is it about standing on concrete floors for long periods that makes people feel more tired than standing for the same time on a wood floor?
The effect is real, we all know that. I think that the difference cannot possibly be due to the hardness of the floor material. The pressure under the foot of a heavy person standing on one foot won’t be more than, say, 40 psi. With that kind of pressure, it can’t be possible to detect any difference in the reaction between a foot and a floor of wood, concrete, steel or even diamond. “Diamonds on the soles of your shoes?)
I think the difference is found in the rate of heat loss between one material and another, but I don’t really know.
Anybody?
I want to convince a potential customer to pour a concrete floor on the main level of her house and then acid stain it herself.
Ron
Replies
That's the first thing I thought of--that concrete is cooler than wood and that it is a better heat sink. When my feet (or muscles anywhere) get cold they ache and feel more tired than when they are warm
I agree. The difference in compressibility between wood and concrete is so tiny as to be totally insignificant.
There can be an effect from a framed floor with the entire floor diaphragm having some bounciness, but that would not be the case for plain concrete vs. wood over concrete, so it cannot explain the true reason.
My theory is the difference in friction between wood and concrete. Concrete is rather grippy so it tends to jar the joints, especially the ankles, and cause movement of the foot within the shoe. We know that movement of the foot within the shoe is uncomfortable, in fact, over time will cause soreness followed by blistering. Wood is more slippery so the joints don't jar nor the foot chafe in the shoe.
I've often wondered the same thing. I don't buy the temperature argument, rather I think it must have something to do with force transfer in the bones of the feet while you're standing. Remember that you're never completely static while standing. Your weight transfers from one part of each foot to another as you do whatever it is you're doing while standing around. Standing on a hard surface, that weight transfer may not be as smooth as it otherwise might be on a softer surface with more capacity to absorb energy.
It should be possible to completely neutralize the effect of standing on a hard floor by wearing better footwear. Anti-fatigue mats do basically the same thing- provide a soft, impact-absorbing layer between the feet and the hard surface.
I don't buy the temp theory.
Why is it that runners will get shin splints while running on concrete but not on asphalt? There feet will hurt more, the impact is much worse on the concrete then the asphalt. Certainly the hardness is as similar as that of the concrete to wood analogy that you suggest.
My house is slab on grade, I notice a significant difference standing in my house over that of a wood subfloor house. There is absolutely no give to the concrete floor where as the wood has some give.
I know your just talking about standing still but do we really do just that for any length of time.
I wouldn't have concrete as a finished floor if I could avoid it.
Doug
Why is it that runners will get shin splints while running on concrete but not on asphalt?
I used to run a lot and still run a little. I've occasionally gotten shin splints when I increased my mileage/frequency too quickly. I don't think shin splints occur more on concrete than asphalt. I know it's commonly stated, but I've looked into it and I can't find any real world evidence. Neither surface absorbs any significant impact. The shoes and your body do that.
-Don
Don
I don't think shin splints occur more on concrete than asphalt. I know it's commonly stated, but I've looked into it and I can't find any real world evidence
I used to run 6 miles a day and if I did it on concrete road as opposed to the running paths I felt a distinct difference. Now I know that's hardly a scientific study but I'm not the only person that has had that experience.
There is plenty evidence out there to show that the surface that we run on has a lot to do with the absorption of the impact.
I don't have any data to back my stupid theory, just the little practical experience and I wouldn't want concrete floors to stand on if I could avoid it.
Doug
I used to run 6 miles a day and if I did it on concrete road as opposed to the running paths I felt a distinct difference. Now I know that's hardly a scientific study but I'm not the only person that has had that experience.
FWIW, I used to spend a lot of time on the newsgroup rec.running. This was always a hot topic (sort of like the helmet threads on the bicycle newsgroups or the tyvek under cedar threads here). In general, most runners feel the way that you do about concrete vs asphalt putting me in the minority. It doesn't mean I'm wrong, but it does mean I'll have a harder time proving I'm right :-).
BTW, I like how you quoted me and put it in red. I did the same (see, I told you I liked it). Is this a convention? If not, it should be.
-Don
A big problem is not wearing shoes. A customer of mine renovated and installed infloor heat in 1½" concrete.
The original floor covering was 85% carpet and 15% tile. The new floor was tile in all the living areas and engineered hardwood in bedrooms.
She had been accustomed to walking barefoot or in thin slippers over all of that carpet. Shortly after moving back in, her legs and feet began to ache terribly.
She bought walking shoes for housework and feels great now.
How do you tell a woman she needs to buy shoes???
Gord
How do you tell a woman she needs to buy shoes???
I've never met one that had to be "told" to buy shoes- they all just did it out of habit. I always figured it was either something genetic, or something they learned in 8th grade health class when they separated the boys and the girls into two separate classes.
Bob
Ok so none of you guys know any more than I do. That's a comfort to me.
Does anybody really know?
Hey Gord, I built a set of shoe shelves a long time ago, floor to ceiling over a width of about 6 -7 feet to hold a vast number of shoes, mostly in boxes. It was part of a bathroom/bedroom/closet reno. The woman's friends came in to see the work. They appeared to be able to see the big bathtub. They could see the colours of things (and describe them in words I didn't understand). They could see the shoe shelves - and they didn't seem to be able to see a single other thing on that complicated job.
So, with that in mind, I'm posing a second question: Do we all have big blind spots or do we all have small areas of vision?
Going to work today, Gord?
Ron
This is just a wild #### guess but, maybe it has something to do with the energy transferred back to the legs when walking.
A wood floor absorbs energy then distributes it over a wide area and perhaps the concrete just reflects it back up the legs.
DCS Inc.
"Whaddya mean I hurt your feelings, I didn't know you had any feelings." Dave Mustaine
A blind spot would infer we are unable to see from a certain perspective. Looking at the same from a different perspective eliminates the blind spot.
I think we have bald spots. Small barren sections of our brain that defy logic. We can comb-over these bald spots to give the appearance of understanding but they will never again bear new fruit.
Work?
8-5 is on hold for the morning and probably the day. Have some estimates and invoicing to prep between shovelling and honey-do's.
Get much snow?Gord
I think it has to do with the impact of the foot on wood vs. concrete. Concrete has no "give", andywhere on the floor. Wood floors will have SOME "give", particularly if you step on the plywood between the floor members. I tried searching on google about this subject, and got about 400,000 hits. Never did find anything useful,
The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy. [Martin Luther King, Jr.]
Gord,
Bald spots! I love it!
Don't tell anybody but I have a toupee (or tou).
Ron
Frikin wind. Frikin snow. I actually had to find the car in the driveway. More snow here than Whit Juan but not as packed, I could walk on 3' drifts after Juan.
Wind is still gusting and filling in what I shoveled this morning.
Cold on the ears and need to keep my brain warm, (more now than ever it seems), so I went back in and put on my toque eh?
You?
Gord
Gord
I was toqued, too, eh?
Which reminds me: my sister is coming for a visit Saturday and bringing a bit of tuktu with her. Soul food.
Ron
I see the hardness theory is popular, but I'm still not buying it. There is considerable cushioning in the foot, and even more in the shoe. All of that cushioning is so much greater than the really really tiny difference in compression between wood and concrete that the difference in floor materials would be entirely insignificant. My judgement tells me there is some other reason other than hardness differences if there really is a comfort difference between wood and concrete.
IMHO someone already said it.
It isnt so much that concrete is harder than wood (though it is) its that there is almos zero resiliency to a concrete slab but a wooden floor will flex. The floor boards may be "hard" but the joists will deflect.
I can be measured - stuck a dial indicator on a pipe spanning the floor and walk by it. (see pg 89 of Taunton's "Renovating a Bathroom" - Dennis Hournay also in issue 124.
Yes, a floor on joist spans would flex and a concrete slab on grade would not. But the question is generally posed as to whether a concrete shop floor should be overlayed with wood, with the claim being that it is more comfortable. In that case deflection would not be the reason because there isn't any pertinent difference in deflection. So, if the claim that wood is more comfortable is true (and I believe it may be) then there must be another reason.
> there is almos zero resiliency to a concrete slab but a wooden floor will flex. The floor boards may be "hard" but the joists will deflect.
In that case, we should see a big difference between slab on grade and those bouncy prestressed multi-story parking structures.
Up in audio frequencies there is a substantial difference. I found out about it building a Foley stage. Foley is a motion picture and TV sound effects process where people watch the picture and make sound effects in sync with what they see. They're called "Foley walkers" because most of what they do is footsteps. It turns out that all successful Foley stages are slab on grade. Anything else produces a hollow sound that doesn't work for footsteps on concrete.
-- J.S.
I don't understand the debate going on here. Concrete is vastly different than a wooden floor. We react less with our feet and legs but they are still tactile and sensitive parts of our body.
Would we be as comfortable working all day at a concrete desk, sitting on a concrete bench? Throw some cushions on a concrete sofa and tell your a55 why the deflection of wood makes so little difference?
The debate should be physiological.
Gord
nothing says Sunday like a toupie hamGord
i actually know this one,
it has to do with "point loads". may seem odd, but there is a "spreading of weight" that occurs in a proportion to the "hardness" of the surface. "hardness" being an actual measure. also the transference of that weight from the floor back into the body. the fella with the shin splints is on to something, only in his case the "point load" is exacerbated by the impact of the running which is a factor greater than just standing.
anyhow, standing on concrete, physiologically speaking, has more impact than a "less hard" surface. softer surfaces actually broaden the reflected impact back to more of the surface of the feet, lessening the pain. think standing in running shoes v. concrete boots (cool mob reference) only in this case the "hardness" of the wood is much closer to that of the concrete than to running shoes though there is a real difference in the "hardness" of wood to concrete
get it?
Merlvem,
Of course there is a difference in hardness between concrete and wood, but it won't become apparent until you're dealing with rather greater pressures than are involved with a human standing on a floor.
I reckon that a heavy person standing on one foot might put a pressure of 40 psi or thereabouts on the floor. At that level of pressure, the difference in deflection between concrete underfoot and wood underfoot is going to be roughly immeasurably small.
I don't believe the hardness of the material can make the slightest bit of difference here since we are only considering materials as hard as or harder than wood. No possible perceptible difference.
Am I wrong? Convince me.
Ron
looking thru my books.....,med school didn't exactly address this, but i'll see what i can find.
ok, here we go
ron, i don't suppose you'd take my word for it......no? sorry about this, it became interesting and got away from me.
there are several different means to measure "hardness", and several different measures of "hardness".
typically wood is measured using the "janka" hardness table. this reflects how much force it takes to embed a 1" steel ball halfway into the surface of a particular wood.....it varies widely.
Douglas Fir 660
So. Yellow Pine (loblolly & short leaf) 690
So. Yellow Pine (longleaf) 870
Black Cherry 950
Teak 1000
Black Walnut 1010
Heart Pine 1225
Iroko - Kambala 1260
Yellow Birch 1260
Red Oak (Northern)1290
American Beech 1300
Ash 1320
White Oak 1360
Australian Cypress 1375
Hard maple 1450
Brazilian Maple 1500
Zebrawood 1575
Wenge 1630
Kempas 1710
African Pedauk 1725
Bamboo 1800
Hickory/Pecan1 820
Purpleheart 1860
Jarrah 1910
Merbau 1925
Sydney Blue 2023
Brushbox 2135
Tigerwood 2160
Santos Mahogany 2200
Mesquite 2345
Brazilian Cherry 2350
Spotted Gum 2473
Bloodwood 2900
Tiete Rosewood 3200
Brazilian Teak 3540
Brazilian Walnut 3620
concrete is often measured in psi, or using the "Mohs" scale of hardness.
psi in concrete ranges from 3,000 or less (for soft concrete) to 8,000 or greater for "critically hard"
having said all that, there are 3 measures of hardness, 1)scratch, 2)indentation, 3)rebound.
Rebound hardness is the most applicable due to our interest in the "transferred" effect of the weight of a person reflected back onto the person.
SO,.....two different measures of hardness for 2 different material types. I found a measure of hardness that covers BOTH wood and concrete,....the Rockwell hardness test.
I frankly don't understand the unit of measure but here are some comparitive #s.
1)balsa=.84
2)pine=2.04
3)birch=2.75
4)cherry=2.88
5)oak=3.20
6)concrete @ 17,000psi=48
7)concrete @ 3,000psi=42
these are results from different tests but seemed to be from my non-engineering mind to be similar. the concrete in some was reinforced, and i don't know how much that would effect the results. i think we can say that concrete is indeed around 15-20 harder than wood.
boy that was a pain in the arse.
OK?
merlvern
I think you misunderstand me. The fact that concrete is harder then wood is not in question. The relevance of that fact is.
Anyway, thanks for the table of wood hardness.
Ron
Wow! that was very educational.
So if I follow, The relative hardness of different species of wood could also translate into mass. The higher the number on your scale, the greater that substance would weigh at the same relative humidity.
No matter how hard the wood, it will warm to the touch. Although, could one assume the higher the wood rates on your scale the longer it would take?
Ron's hypothesis, if I am correct, is standing on concrete is tiring because it is a heat sink. Even concrete with in-slab heat and 70º will remove heat from a 98.6º body.
One or the other does not seem to explain the feel of standing on concrete. Maybe it is a combination of hardness and heat loss.Gord
hey there,it's really mostly about a surface's ability to "reflect" weight which is (i forget exactly the equation....please don't make me look it up) a combination of gravity and mass. anyhow, the point is that there is a relationship between the hardness of a surface and the resultant "rebound" of force back into the body, the harder the surface, the more that weight is reflected back into the body. additionally, the harder the surface, the more you experience "point loads" due to the surfaces inability to "spread" the force. essentially, the harder the surface, the more it seems as if you are standing on a "sharper" object.
"I want to convince a potential customer to pour a concrete floor on the main level of her house and then acid stain it herself."
And yet you admit that "The effect is real, we all know that."
If your customer is reluctant because he/she is concerned about the hardness (comfort) of the concrete and you "win" the point, don't expect the customer to like you much after he/she stands on that floor for a few days.
"I think that the difference cannot possibly be due to the hardness of the floor material."
I disagree. I think there is a significant difference between hardness of concrete (or tile) and the hardness of wood.
Rich Beckman
Another day, another tool.
Hi Rich, It's been a while.....
The thing is that I believe the difference we feel between spending a long time on a concrete floor and the same time on a wood floor is mainly due to the difference in the rate of heat loss. I think that if she had a nice warm concrete floor, she'd love it and not think about the floor being hard. (Until summer)
An acid stained concrete overpour on this job might cost a couple thousand less than a wooden floor, especially if she stained it herself. That would make the project a couple thousand dollars closer to reality.
I gather that nobody really knows whether my theory is crap or not, including me. As for the concrete being harder than wood, well I know that, don't I? I'm not nearly the simpleton you've been told I am. I think that at the very low pressures concerned, the hardness makes no difference. It's like putting a feather in the middle of a 2 x 10 joist and another feather in the middle of a steel I joist and saying the difference in deflection is due to the difference in the modulus of elasticity. WHAT difference in deflection? Sure it is real and calculable but so what!
Anyway, I can easily be convinced I'm wrong, but not by more reiterations of the comparative hardness of materials.
Ron
Ron,
My only problem with your 'heat sink' approach is that my legs get tired on concrete even in Florida. Don't believe me? Take a trip to Florida. Spend the first day standing on the concrete next to a pool (don't actually get in, this is science after all). Spend another day sitting in the pool to soak your dogs. Then spend another day standing on a wooden deck. On which day were your feet and legs the most tired? Keep in mind that the concrete is warmer than your body, so the heat sink theory doesn't apply here.
Concrete also tires me out when I am wearing shoes and socks. Presumably there isn't a lot of heat loss at that time.
If the concrete floors are the difference between her being able to afford the house and not afford it, I'd say she can't afford it.
Aimless,
Now here's some useful information tha I would never know. Thank you. The only times I've ever been anywhere hot I've been pretty much confined to walking on steel decks. I didn't really find them all that bad, and that is part of the background to the heat loss theory.
As for the cost, the floor thing is not the only factor in play.
Ron
I'm still with you, Ron.
If you placed a shoe on a concrete floor and placed the same shoe on a concrete floor with a sheet of plywood laying on it, then pressed down against the inside of the sole of the shoe with any possible instrument it would be impossible to detect by any measure of hardness or deflection whether the shoe was on concrete or on wood. Therefore, differences in the hardness of the two materials cannot explain the reason why wood is apparently more comfortable than concrete.
I dont think its the hardness at all, but the heat conduction path out of your feet effecting circulation.
Anyone who has ever sat on wet concrete during lunch on a job site knows that it drains the energy right out of you. This is the extreme case. Standing on the concrete all day drains a lot. Try standing on a thin piece of masonite or cardboard instead of concrete, which is not gonig to add much flex - you will notice the difference.
wayneL5
Precisely what I'm thinking.
This has been on my nimd a bit lately since I just moved into a house I built with two levels of heated concrete floor and one level of hard maple and tile. The wood floor isn't heated.
I don't spend any more time on my feet than I can help but I prefer the concrete because I like the warmth. I really love working in the kitchen where I can feel the warm spots in the floor and then move 3 inches away to a cooler area. The contrast makes me aware of the floor more than I normally would be.
The potential customer works in a hospital and is on her feet all day. This is important.
Ron
Ron
I have another experiment. Take your fist and punch the plywood set on the concrete floor as hard as you can. Now remove the plywood and punch the concrete as hard as you can. No measurable differrence?
Your feet and legs are as sensitive as your fingers. Possibly more, a feather brushed over my hand doesn't bother me, over my feet is almost unbearable.
Every person can distinguish the difference between walking on grass, gravel, dirt, concrete, asphalt, wood. Even in shoes you can feel a pebble or a root on a path.
A finished, heated, stained concrete floor is beautiful and functional, but some throw carpets and engineered hardwood make it livable.Gord
"what is it about standing on concrete floors for long periods that makes people feel more tired than standing for the same time on a wood floor"
Think about what you're doing. IF you spend alot of time on concrete, it is probably in a shop or a commercial kitchen or a warehouse or some other place of work, and most likely you are working. If I spend all day in my basement or my garage, then its probably because I'm working on some project all day long. At the end of that long day, my legs, knees and feet will complain about it. AND it is something I'm not used to doing any more (unfortunately I do not get to spend all day on my feet working on projects that often), so much more of the "effect".
Really, how often do you stand all day on a wood floor? How often to stand all day? How often do you get to compare all day on your feet on one surface one day and the same on the other surface the next day? I bet, on all of the above, rarely if ever to really do you get to compare the two and the difference is a perception more so than a reality.
Tim
I think you're onto something. For a lot of people, their work demands they spend a lot of time on their feet on a concrete or tile floor, then they go home, look at the wood floor, put their feet up and think about how much better they feel now they are off the concrete floor. Then credit the difference in the hardness of the floors for the difference in the way they feel.
Ron
There maybe some point to that - but having worked on both a lot, I still belive it is the heat conduction. I tried to keep eveything under me dry if possible. Even flipping over a plank to get the dry side up (for 10 minutes!) on scaffoling on a rainy day makes a difference.
Expreince from home:
Last house: garage had a concrete floor poured on gravel / dirt. It was cold in the winter, so I often stood on carpet. I had a propane heater, so the room was warm but the floor was cold.
Current house: garage floor is concrete poured over a joist system, so we ahve living space under it. I have the pellet stove down there, so my garage floor is about 66-68 degrees all the time. Huge difference - never needed a piece of run to feel comfortable.