How necessary is gravel under concrete?
I'm wanting to put a 20 foot concrete pad in front of my garage. Right
now, the garage floor is concrete, but the driveway in front is just dirt. However, under that dirt, there is a bed of 2" to 3" rock, which I put there about 6 years ago. What I want to do is just make forms and have a just have a few yards of concrete delivered, to trowel myself. The base dirt is well packed and solid from years of driving on it. To add gravel, I will have to disturb this well packed dirt with the rock underneath. (or the drive will be higher than the garage floor). Not only will this disturb the well packed base, but will double the cost of this job, because of the cost of the gravel, and the cost to rent some sort of machinery to dig up this dirt and rock base, since I already tried a shovel and with that rock base, the shovel wont even go in the ground unless it's after a rain when it's muddy, and even then the rock base could not be dug up with just a shovel. My plan was to simply make forms, remove the small wooden ramp I made at the front edge of the concrete garage floor (I left the dirt about 4 inches lower than the garage floor intending to pour concrete, but made that ramp out of stacked 2x8's to drive in and out of the garage). Add a few bricks with some rebar on top, And pour/finish the concrete. A fairly simple job. However, someone told me I must put dravel under it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. One other thing. For a 20 foot long by 12 foot wide strip of concrete, how many joints should I cut in the concrete? I'm thinking just one, so each section is 10ft. I plan to place one of those black fiber strips where it meets the garage slab. I'll probably just trowel the joint in the middle, to avoid having to rent a concrete saw. Finally, did I figure this correctly? 20 X 12 = 240 sq ft. At 4 inches think, I estimated that I need roughly 3 cubic yards of concrete. (Actually 2.96 cu yd). Is this right? (I'm not the best at math). Thanks |
How necessary is gravel under concrete?
A fairly simple job. However, someone told me I must put dravel under
it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. You say nothing about your climate or location. Do you have freeze thaw cycles? Gravel base helps keep the water away from the concrete. Do you have seasons? Dry, wet cycles? Soil expands when it gets wet and shrinks when it dries. Rock helps isolate the concrete from soil movement. When the soil is wet its load carrying capacity is diminished. Concrete corners may not have good support and break. Generally rock under concrete is essential. Especially under driveways where there is loading from vehicles. A thin layer of sand under the concrete allows up to 10 feet between joints. The joints control where the concrete cracks. If the joints are too far apart then a crack forms before the joint is reached. The sand allows a little slippage so the joints can be stretched a little. I figure 2.7 yards. |
How necessary is gravel under concrete?
Pat wrote: A fairly simple job. However, someone told me I must put dravel under it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. You say nothing about your climate or location. Do you have freeze thaw cycles? Gravel base helps keep the water away from the concrete. Do you have seasons? Dry, wet cycles? Soil expands when it gets wet and shrinks when it dries. Rock helps isolate the concrete from soil movement. When the soil is wet its load carrying capacity is diminished. Concrete corners may not have good support and break. Generally rock under concrete is essential. Especially under driveways where there is loading from vehicles. A thin layer of sand under the concrete allows up to 10 feet between joints. The joints control where the concrete cracks. If the joints are too far apart then a crack forms before the joint is reached. The sand allows a little slippage so the joints can be stretched a little. I figure 2.7 yards. And no rebar? |
How necessary is gravel under concrete?
I would recommend putting a 1'X1' footing adjacent to your garage slab
and one at the end of your new slab, also. Put an expansion joint at the center of your pour by placing a physical divider there. Just cutting a kerf in the concrete (after it sets up well?) is not a proper expansion joint and may likely not work to prevent the slab from cracking somewhere else. Order 3000psi concrete. Costs the same as 2500 psi. |
How necessary is gravel under concrete?
On Apr 27, 1:05*am, Tony Hwang wrote:
Pat wrote: A fairly simple job. *However, someone told me I must put dravel under it first. *Is this gravel really needed? *If it is, why? *After all, I already have the rock base, which is very solid, and rock is like gravel. *It's just that dirt has filled in around the rock so it just looks like dirt now. You say nothing about your climate or location. *Do you have freeze thaw cycles? *Gravel base helps keep the water away from the concrete. *Do you have seasons? *Dry, wet cycles? *Soil expands when it gets wet and shrinks when it dries. *Rock helps isolate the concrete from soil movement. *When the soil is wet its load carrying capacity is diminished. *Concrete corners may not have good support and break. *Generally rock under concrete is essential. *Especially under driveways where there is loading from vehicles. A thin layer of sand under the concrete allows up to 10 feet between joints. The joints control where the concrete cracks. *If the joints are too far apart then a crack forms before the joint is reached. *The sand allows a little slippage so the joints can be stretched a little. I figure 2.7 yards. And no rebar?- Hide quoted text - - Show quoted text - |
How necessary is gravel under concrete?
On Apr 27, 1:05*am, Tony Hwang wrote:
And no rebar?- Rebar for footings, yes. It's also a good idea to use reinforcement wire on any large slab. |
How necessary is gravel under concrete?
On Fri, 27 Apr 2012 00:05:55 -0600, Tony Hwang
wrote: Pat wrote: A fairly simple job. However, someone told me I must put dravel under it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. You say nothing about your climate or location. Do you have freeze thaw cycles? Gravel base helps keep the water away from the concrete. Do you have seasons? Dry, wet cycles? Soil expands when it gets wet and shrinks when it dries. Rock helps isolate the concrete from soil movement. When the soil is wet its load carrying capacity is diminished. Concrete corners may not have good support and break. Generally rock under concrete is essential. Especially under driveways where there is loading from vehicles. A thin layer of sand under the concrete allows up to 10 feet between joints. The joints control where the concrete cracks. If the joints are too far apart then a crack forms before the joint is reached. The sand allows a little slippage so the joints can be stretched a little. I figure 2.7 yards. And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. All were poured on just sand without any gravel. Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. Of course one reason is probably to keep costs down. |
How necessary is gravel under concrete?
"Doug" wrote:
And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. All were poured on just sand without any gravel. Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. Of course one reason is probably to keep costs down. I like some iron in there, too-- but I keep hearing folks who know a lot more about it than I do say that the fiberglass right in the mix is a better binder. To a casual observer it looks like there is *no* reinforcement, but it is in the mix. Jim |
How necessary is gravel under concrete?
On 4/27/2012 8:22 AM, Jim Elbrecht wrote:
wrote: And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. All were poured on just sand without any gravel. Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. Of course one reason is probably to keep costs down. I like some iron in there, too-- but I keep hearing folks who know a lot more about it than I do say that the fiberglass right in the mix is a better binder. To a casual observer it looks like there is *no* reinforcement, but it is in the mix. Jim There'll be 1/2" rebar on two foot centers in any slab i own. No steel in concrete is just stupid. -- Steve Barker remove the "not" from my address to email |
How necessary is gravel under concrete?
On Apr 27, 6:22*am, Jim Elbrecht wrote:
"Doug" wrote: And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. *All were poured on just sand without any gravel. *Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. *Of course one reason is probably to keep costs down. I like some iron in there, too-- * but I keep hearing folks who know a lot more about it than I do say that the fiberglass right in the mix is a better binder. * *To a casual observer it looks like there is *no* reinforcement, but it is in the mix. Jim Been told also that rebar and wire are an 'old wive's tale' and not necessary today. And, worse, a huge nuisance if you try to break it up and remove later. |
How necessary is gravel under concrete?
On Fri, 27 Apr 2012 09:22:15 -0400, Jim Elbrecht
wrote: "Doug" wrote: And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. All were poured on just sand without any gravel. Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. Of course one reason is probably to keep costs down. I like some iron in there, too-- but I keep hearing folks who know a lot more about it than I do say that the fiberglass right in the mix is a better binder. To a casual observer it looks like there is *no* reinforcement, but it is in the mix. Jim Probably right but for residential work, probably overkill besides the expense. I still like mesh but so far I haven't seen it in residential driveways and except for once, never in sidewalks neither. As someone pointed out, reinforced concrete will be harder to remove. |
How necessary is gravel under concrete?
On Fri, 27 Apr 2012 07:39:06 -0500, "Doug"
wrote: On Fri, 27 Apr 2012 00:05:55 -0600, Tony Hwang wrote: Pat wrote: A fairly simple job. However, someone told me I must put dravel under it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. You say nothing about your climate or location. Do you have freeze thaw cycles? Gravel base helps keep the water away from the concrete. Do you have seasons? Dry, wet cycles? Soil expands when it gets wet and shrinks when it dries. Rock helps isolate the concrete from soil movement. When the soil is wet its load carrying capacity is diminished. Concrete corners may not have good support and break. Generally rock under concrete is essential. Especially under driveways where there is loading from vehicles. A thin layer of sand under the concrete allows up to 10 feet between joints. The joints control where the concrete cracks. If the joints are too far apart then a crack forms before the joint is reached. The sand allows a little slippage so the joints can be stretched a little. I figure 2.7 yards. And no rebar? I like the idea of rebar (or even mesh) in residential driveways but I've yet to see it in the dozen or so driveways under construction I've come across on Long Island or in Houston. All were poured on just sand without any gravel. Personally I like the idea of sand, gravel and rebar but that's not what I've seen so far. Of course one reason is probably to keep costs down. When rebar is used, how do they keep it IN the concrete, so it's not laying right on the ground? I figured I'd lay it across bricks, or pieces of broken patio blocks because bricks are a little too thick. As far as mesh, the seems like it would be much harder to keep off the ground. --- * Message Posted by computer - Cell phones kill from radiation * |
How necessary is gravel under concrete?
used improper usenet message composition style
by unnecessarily full-quoting: When rebar is used, how do they keep it IN the concrete, so it's not laying right on the ground? Rebar Chairs: http://www.quadlock.com/images/icf_c...bar_Chairs.png http://www.concreteconstruction.net/...m45-984353.jpg http://i00.i.aliimg.com/photo/v0/222...ebar_Chair.jpg As far as mesh, the seems like it would be much harder to keep off the ground. Any of those re-bar chairs could also be used for wire mesh. |
How necessary is gravel under concrete?
|
How necessary is gravel under concrete?
|
How necessary is gravel under concrete?
|
How necessary is gravel under concrete?
|
How necessary is gravel under concrete?
On Apr 26, 11:55*pm, wrote:
I'm wanting to put a 20 foot concrete pad in front of my garage. *Right now, the garage floor is concrete, but the driveway in front is just dirt. *However, under that dirt, there is a bed of 2" to 3" rock, which I put there about 6 years ago. *What I want to do is just make forms and have a just have a few yards of concrete delivered, to trowel myself. The base dirt is well packed and solid from years of driving on it. To add gravel, I will have to disturb this well packed dirt with the rock underneath. *(or the drive will be higher than the garage floor). Not only will this disturb the well packed base, but will double the cost of this job, because of the cost of the gravel, and the cost to rent some sort of machinery to dig up this dirt and rock base, since I already tried a shovel and with that rock base, the shovel wont even go in the ground unless it's after a rain when it's muddy, and even then the rock base could not be dug up with just a shovel. My plan was to simply make forms, remove the small wooden ramp I made at the front edge of the concrete garage floor (I left the dirt about 4 inches lower than the garage floor intending to pour concrete, but made that ramp out of stacked 2x8's to drive in and out of the garage). *Add a few bricks with some rebar on top, And pour/finish the concrete. A fairly simple job. *However, someone told me I must put dravel under it first. *Is this gravel really needed? *If it is, why? *After all, I already have the rock base, which is very solid, and rock is like gravel. *It's just that dirt has filled in around the rock so it just looks like dirt now. One other thing. *For a 20 foot long by 12 foot wide strip of concrete, how many joints should I cut in the concrete? *I'm thinking just one, so each section is 10ft. *I plan to place one of those black fiber strips where it meets the garage slab. *I'll probably just trowel the joint in the middle, to avoid having to rent a concrete saw. Finally, did I figure this correctly? 20 X 12 = 240 sq ft. *At 4 inches think, I estimated that I need roughly 3 cubic yards of concrete. *(Actually 2.96 cu yd). *Is this right? *(I'm not the best at math). Thanks Many times gravel is used to bring the grade up to a 4 inch pour. Gravel is cheaper than concrete. Sand may wash away from under the concrete. I advise against using sand unless you are sure it won't wash away. Rule of thumb is figure 1 yard will do 80 sq.ft. at 4 inches. So, your math is correct. One more thing to think about is to drop the concrete approx. 1 inch below the entrance of the garage floor. This will serve 2 purposes. One is that water won't enter under the garage door if you get a sudden wind driven down-pour of rain. The other is if there is a cold snap and the outside concrete heaves up a little. Since the pour is only 20x12, I wouldn't worry about the gravel for drainage too much if you have a good slope to the pour ( 1 inch in 10 ft ). I wouldn't drive on it for at least a week, 3 weeks is recommneded. Do not let anything heavy, like a car, sit in one spot very long. Even after a year of curing, a heavy object will cause the concrete to develop low spots ( puddles). Good luck. Hank |
How necessary is gravel under concrete?
On Sat, 28 Apr 2012 03:38:47 -0700 (PDT), Hank
wrote: On Apr 26, 11:55*pm, wrote: I'm wanting to put a 20 foot concrete pad in front of my garage. *Right now, the garage floor is concrete, but the driveway in front is just dirt. *However, under that dirt, there is a bed of 2" to 3" rock, which I put there about 6 years ago. *What I want to do is just make forms and have a just have a few yards of concrete delivered, to trowel myself. The base dirt is well packed and solid from years of driving on it. To add gravel, I will have to disturb this well packed dirt with the rock underneath. *(or the drive will be higher than the garage floor). Not only will this disturb the well packed base, but will double the cost of this job, because of the cost of the gravel, and the cost to rent some sort of machinery to dig up this dirt and rock base, since I already tried a shovel and with that rock base, the shovel wont even go in the ground unless it's after a rain when it's muddy, and even then the rock base could not be dug up with just a shovel. My plan was to simply make forms, remove the small wooden ramp I made at the front edge of the concrete garage floor (I left the dirt about 4 inches lower than the garage floor intending to pour concrete, but made that ramp out of stacked 2x8's to drive in and out of the garage). *Add a few bricks with some rebar on top, And pour/finish the concrete. A fairly simple job. *However, someone told me I must put dravel under it first. *Is this gravel really needed? *If it is, why? *After all, I already have the rock base, which is very solid, and rock is like gravel. *It's just that dirt has filled in around the rock so it just looks like dirt now. One other thing. *For a 20 foot long by 12 foot wide strip of concrete, how many joints should I cut in the concrete? *I'm thinking just one, so each section is 10ft. *I plan to place one of those black fiber strips where it meets the garage slab. *I'll probably just trowel the joint in the middle, to avoid having to rent a concrete saw. Finally, did I figure this correctly? 20 X 12 = 240 sq ft. *At 4 inches think, I estimated that I need roughly 3 cubic yards of concrete. *(Actually 2.96 cu yd). *Is this right? *(I'm not the best at math). Thanks Many times gravel is used to bring the grade up to a 4 inch pour. Gravel is cheaper than concrete. Sand may wash away from under the concrete. I advise against using sand unless you are sure it won't wash away. Wash away??? Yes it can but not common. Rule of thumb is figure 1 yard will do 80 sq.ft. at 4 inches. So, your math is correct. One more thing to think about is to drop the concrete approx. 1 inch below the entrance of the garage floor. This will serve 2 purposes. One is that water won't enter under the garage door if you get a sudden wind driven down-pour of rain. The other is if there is a cold snap and the outside concrete heaves up a little. 1 inch to me sounds like a lot but I guess a judgement call. I think you have a good suggestion at least for water tho I still would try to slope the driveway away from garage if possible. I've seen driveways in NY and I haven't seen heave problems but I suppose it's possible, just haven't seen it. Good suggestion tho to ?? inches below entrance to garage. Since the pour is only 20x12, I wouldn't worry about the gravel for drainage too much if you have a good slope to the pour ( 1 inch in 10 ft ). I wouldn't drive on it for at least a week, 3 weeks is recommneded. Do not let anything heavy, like a car, sit in one spot very long. Even after a year of curing, a heavy object will cause the concrete to develop low spots ( puddles). That's what I would have thought (about the one week) but I've seen industrial setting where light traffic was allowed after just 3 to 4 days. I think I heard it's ok because concrete is about at half strength then. I know I was very nervous when I first learned of this. Regardless, three weeks is overkill for most residential driveways unless you are going to have a lot of turning or heavy vehicles other than cars. |
How necessary is gravel under concrete?
On Apr 28, 8:48*am, "Doug" wrote:
Wash away??? * *Yes it can but not common. 1 inch to me sounds like a lot but I guess a judgement call. * I think you have a good suggestion at least for water tho I still would try to slope the driveway away from garage if possible. *I've seen driveways in NY and I haven't seen heave problems but I suppose it's possible, just haven't seen it. * Good suggestion tho to ?? inches below entrance to garage. That's what I would have thought (about the one week) but I've seen industrial setting where light traffic was allowed after just 3 to 4 days. *I think I heard it's ok because concrete is about at half strength then. *I know I was very nervous when I first learned of this. * Regardless, three weeks is overkill for most residential driveways unless you are going to have a lot of turning or heavy vehicles other than cars. I agree that sand washing away is uncommon. But if the underside of the pour is exposed, it happens. Keeping dirt, sod and etc. next to the concrete does away with the washing out of sand. Since neither of us can see the site, shoot it for grade, or know the climate, I am just offering suggestions. When my garages were built, I had the men drop the concrete about a half inch, just inside the door ( like a little pocket the door sat in) and it went out to the skirt. Then the skirt dropped another half inch below that. Believe me it helps in the pour rains and heaving here in Ohio. Also, I didn't put my e450 van on my new concrete for over a month. I parked it in a spot and didn't drive it for a couple months later. Now I have 4 little puddles where the concrete sagged. A year later a friend parked his 6X12 enclosed trailer in another spot for a few months and the concrete still sagged and created small puddles. Drivng over it probably won't do that as much as just leaving something sit on it. Also, I have seen bus stops and exits where there is 8-12 inches of concrete pads with rebar and it still sags over time becaues of the weight. Hank ~~~~ learned from experience :-( |
How necessary is gravel under concrete?
On Sat, 28 Apr 2012 07:34:20 -0700 (PDT), Hank
wrote: On Apr 28, 8:48*am, "Doug" wrote: Wash away??? * *Yes it can but not common. 1 inch to me sounds like a lot but I guess a judgement call. * I think you have a good suggestion at least for water tho I still would try to slope the driveway away from garage if possible. *I've seen driveways in NY and I haven't seen heave problems but I suppose it's possible, just haven't seen it. * Good suggestion tho to ?? inches below entrance to garage. That's what I would have thought (about the one week) but I've seen industrial setting where light traffic was allowed after just 3 to 4 days. *I think I heard it's ok because concrete is about at half strength then. *I know I was very nervous when I first learned of this. * Regardless, three weeks is overkill for most residential driveways unless you are going to have a lot of turning or heavy vehicles other than cars. I agree that sand washing away is uncommon. But if the underside of the pour is exposed, it happens. Keeping dirt, sod and etc. next to the concrete does away with the washing out of sand. Since neither of us can see the site, shoot it for grade, or know the climate, I am just offering suggestions. When my garages were built, I had the men drop the concrete about a half inch, just inside the door ( like a little pocket the door sat in) and it went out to the skirt. Then the skirt dropped another half inch below that. Believe me it helps in the pour rains and heaving here in Ohio. Also, I didn't put my e450 van on my new concrete for over a month. I parked it in a spot and didn't drive it for a couple months later. Now I have 4 little puddles where the concrete sagged. A year later a friend parked his 6X12 enclosed trailer in another spot for a few months and the concrete still sagged and created small puddles. Drivng over it probably won't do that as much as just leaving something sit on it. Also, I have seen bus stops and exits where there is 8-12 inches of concrete pads with rebar and it still sags over time becaues of the weight. Hank ~~~~ learned from experience :-( Earlier when you said an 1 inch drop I was thinking 1/2 inch myself but it is a judgement call of course. Yep, I won't argue with experience ... |
How necessary is gravel under concrete?
On Sat, 28 Apr 2012 03:38:47 -0700 (PDT), Hank
wrote: Many times gravel is used to bring the grade up to a 4 inch pour. Gravel is cheaper than concrete. Sand may wash away from under the concrete. I advise against using sand unless you are sure it won't wash away. Rule of thumb is figure 1 yard will do 80 sq.ft. at 4 inches. So, your math is correct. One more thing to think about is to drop the concrete approx. 1 inch below the entrance of the garage floor. This will serve 2 purposes. One is that water won't enter under the garage door if you get a sudden wind driven down-pour of rain. The other is if there is a cold snap and the outside concrete heaves up a little. Since the pour is only 20x12, I wouldn't worry about the gravel for drainage too much if you have a good slope to the pour ( 1 inch in 10 ft ). I wouldn't drive on it for at least a week, 3 weeks is recommneded. Do not let anything heavy, like a car, sit in one spot very long. Even after a year of curing, a heavy object will cause the concrete to develop low spots ( puddles). Good luck. Hank Thanks for all the replies I'll look up those plastic rebar chairs. I plan to order 3.5 yards to make sure I have enough. I have a barn with a small feed room, and want to put concrete in there too. What ever excess concrete is left over will go in there. The room is only 6 ft wide, so I'll just have a 6 foot 2x4 that I can move to accomodate whatever is left over. Whatever part of that room is not covered, I can do later with bagged concrete, since I have a concrete mixer. But 3 yards is too much to mix by hand. I'm assuming that when I use rebar, in both directions, that I skip the place where there is a joint. In a 20ft run, that should only be one joint. Thanks |
How necessary is gravel under concrete?
replying to tangerine3 , Sid in Sacramento wrote:
tangerine3 wrote: I'm wanting to put a 20 foot concrete pad in front of my garage. Right now, the garage floor is concrete, but the driveway in front is just dirt. However, under that dirt, there is a bed of 2" to 3" rock, which I put there about 6 years ago. What I want to do is just make forms and have a just have a few yards of concrete delivered, to trowel myself. The base dirt is well packed and solid from years of driving on it. To add gravel, I will have to disturb this well packed dirt with the rock underneath. (or the drive will be higher than the garage floor). Not only will this disturb the well packed base, but will double the cost of this job, because of the cost of the gravel, and the cost to rent some sort of machinery to dig up this dirt and rock base, since I already tried a shovel and with that rock base, the shovel wont even go in the ground unless it's after a rain when it's muddy, and even then the rock base could not be dug up with just a shovel. My plan was to simply make forms, remove the small wooden ramp I made at the front edge of the concrete garage floor (I left the dirt about 4 inches lower than the garage floor intending to pour concrete, but made that ramp out of stacked 2x8's to drive in and out of the garage). Add a few bricks with some rebar on top, And pour/finish the concrete. A fairly simple job. However, someone told me I must put dravel under it first. Is this gravel really needed? If it is, why? After all, I already have the rock base, which is very solid, and rock is like gravel. It's just that dirt has filled in around the rock so it just looks like dirt now. One other thing. For a 20 foot long by 12 foot wide strip of concrete, how many joints should I cut in the concrete? I'm thinking just one, so each section is 10ft. I plan to place one of those black fiber strips where it meets the garage slab. I'll probably just trowel the joint in the middle, to avoid having to rent a concrete saw. Finally, did I figure this correctly? 20 X 12 = 240 sq ft. At 4 inches think, I estimated that I need roughly 3 cubic yards of concrete. (Actually 2.96 cu yd). Is this right? (I'm not the best at math). Thanks From my understanding of concrete, you have to make it thicker that two inches minimum, to keep it from cracking easily. With that said, I would buy some wire mesh to keep it together, in the event it does crack. The job seems pretty large for one person, as the saying goes," concrete waits for nobody ". I would enlist the help from a concrete worker from Craigs list ? The wire mesh will run you about seven dollars a piece at Home Depot. Here is a website that u can use to calculate how much concrete you will need. http://www.concretenetwork.com/concr...calculator.htm -- |
How necessary is gravel under concrete?
replying to Robert Macy, Cynthia O. wrote:
I am only replying because others may read it....even though it is a 5-year old question. Using rebar OR WWF (you don't need both) in concrete is not only the right thing to do, but is the smart thing to do. Those who say it is "old" do not know concrete and its ability to crack. Concrete has excellent compressive strength, but poor tensile strength. Code requires certain concrete applications to have either rebar or WWF (Welded Wire Fabric AKA WWMesh). You put rebar rods in footers (on chairs), and you put WWF in slabs (on chairs). This places the rebar / WWF off the ground, and into the concrete where it is doing what it is supposed to do. -- for full context, visit https://www.homeownershub.com/mainte...te-694985-.htm |
How necessary is gravel under concrete?
replying to tangerine3, Cynthia O. wrote:
Rebar sits in chairs. The newer chairs do not require wire ties around the rebar, and are optional. At least 2 rows of rebar, placed parallel, and equal distance in the concrete footer, are required. WWF is used in slabs, and also sit in chairs to keep it off the ground and at the correct height. -- for full context, visit https://www.homeownershub.com/mainte...te-694985-.htm |
All times are GMT +1. The time now is 08:43 PM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter