DIY concrete slab for garden shed
Hello all,
I’ve just purchased a prefab cedar garden shed (8×12) and I’m looking for some advice on the foundation. I would like to install a floating concrete slab and I have a few questions.
1. What is the best way to prepare the site? IE how deep should I excavate and how much and what type of gravel for the base. I’m having some gravel delivered for some interlock and was wondering if this type of gravel would be ok. Its a mixture of coarse sand and small stones.
2. How deep/thick should the pad be? I was planning on using 2x8s for the forms.
3. Does the pad need re-bar?
4. How difficult is it to finish the cement? Is this a DIY or should I hire someone. I’m pretty handy and I have a hand trowel.
5. Anything else I need to consider?
Thanks in advance, Patrick
- A fanatic is one who can’t change his mind and won’t change the subject.View Image
Replies
First of all have you verified that you can do that in your city.
Someplaces allow auxillary structures without inspects as long as they are not on permanate bases.
Other places require permanate bases and maybe a permit and maybe not.
As to your question, what is your location, what kind of soil conditions, and are you going to use it for anything heaver than "ordinary" lawn equipment?
I will leave it to other about the specifics of the slab.
But something like this is a good place to learn concrete work. So what is it is a little rough or slopes a little.
OK, now I think this is the kind of question from a DIYer that I might find annoying and tempt me to reply sarcastically if I was a "regular"- hats off to you for not doing so.
It seems to me that people should at least read a friggin book or two on masonry and THEN come to ask questions to clarify. JMO.
No offense to the person asking the question intended.
Offence?
Maybe you should just change your ID to "Grumpy Ol' House Fan"
Then we could expect this kind of response....
Cheers!
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
Offence?
No, offense. English not your first language?
Maybe you should just change your ID to "Grumpy Ol' House Fan"
Then we could expect this kind of response....
No, thanks, I wasn't making a personal comment - but then I'm not surprised that you would - people too lazy to learn about what they want to do without expecting to be spoon-fed are expected to do that.
Cheers!
Seinfeld!
form it with 1x4, stake down every two feet. you do not need gravel, some people use it but only needed with wet soil. you do not need rebar. not enough weigh for rebar to react. form it and pour it, very simple.
And the purpose of this forum is what?
Why, to let GrumpyOldHouseFan respond with vitriol when he can't think of something nice to say, of course.
Amateurs welcome....ALWAYS
SamT
Insults, back handed compliments, and denigrations.
Followed by
>>No offense to the person asking the question intended.
That'll make everything all right, eh?
SamT
>>No offense to the person asking the question intended.
That'll make everything all right, eh?
Yeah, I think so, I was trying to convey the fact it wasn't personal - I was addressing the post, not the poster. I guess some people can't grasp that concept and apparently have paper-thin skin.
Are you as concerned when the "regulars" attack someone personally rather than their post? Hmmm? Or is it the fact that I tried to avoid having it taken personally that disturbs you so?
You been attacked by regulars here alot? You sure have a problem with that term.
Shout out to Andy C. Namaste my friend.
http://www.hay98.com/
No, not really. I was just trying to be kind by using "regulars."
My comments come from my own observations of what occurs here on a regular basis - I don't believe I indicated they were directed at me.
Thanks for your concern!
I guess I've not noticed any "regular" versus new guy harrasment. Care to point some out? You have a 2X6 chip on your shoulder for some reason.
Shout out to Andy C. Namaste my friend.
http://www.hay98.com/
Oh, I've noticed it - the "usual suspects" get their chance to puff themselves up by attacking others. Pathetic little creatures.
So you don't have any current exmaples.
Are you a troll? Are you here because you need some place to go and harrass people? I haven't seen you post anything but nit picking B.S. Is there a reason you came here and started flaming people?
Mister Kohler is this you?
Shout out to Andy C. Namaste my friend.
http://www.hay98.com/
Oh, get over yourself. I haven't "flamed" anyone. I have commented on posts that were made and my comments were ON-topic.
If the little boys and their delicate sensibilities are too fragile for a different opinion, I suggest they work on that with a professional.
As I stated before, I have not "flamed" anyone - that's a lie. I will however respond in-kind to any cretins who can't muster brain cells to offer a reasoned response and resort to personal attacks.
In other words, I'm not LOOKING for trouble, but I've never walked away from it and never will.
Here is yet another great description of grumpy ol'......
http://www.syzygyjob.net/evaluation/messages/14739.shtml
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
LOL "Hey, fellow Turds.....Look! See! See! See! Here's something ELSE I don't like - how about you all pile on so I don't feel so inadequate? Please! I'm desperate - I hate it when people show me for what I am and I can't handle it by myself!"
Last time I saw behavior like this it was from teenagers in Middle School - except they left themselves with some dignity.
Pretty much sums it up.
Shout out to Andy C. Namaste my friend.
http://www.hay98.com/
Patrick,
If no one feeds him, maybe he'll go away.
SamT
For a two month "Regular", you make a lot of noise....
Not much useful information though.
Joe H
Uh huh. Good one. ::::::eyeroll:::::: Let me know when you have something intelligent to say - I'll buy you a cake.
Oh he just won't give up huh? I have noticed that his posts run pretty much all through the day so I'm beginning to think he's a welfare bum. And with that attitude he's prob. a drunk that's lost his wife, kids, etc... So now he hangs out here all day much like some of the suburban moms on my street. Trying to bring others down to his level. Please check out the link below. I think you'll find it amusing. The only thing missing is a pic of Grumpy as an example.
All I have is one final thing to say to him: Just by looking at the responses to my post I'll say that you're pretty much alone in opinion. If you really feel as you say you do, don't post! This forum won't miss you, its that's simple, even for a simpleton...... If you gave out advice (which I doubt) and someone, for one reason or another, screws it up, how is that your problem? And how is that mine, or ours? heh??
http://curezone.com/forums/troll.asp
To everyone else who has been so helpful, a most whole-hearted thanks again. You are what makes forums like these great.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
Yeah, OK , Cowboy. Like I said earlier, you clearly lack the ability to say something intelligent so you revert to wild and inaccurate smears about me to cover your own obvious inadequacies. What a pathetic (and lazy) little turd.
As far as being "alone," in my opinion - I have no problem with that whatsoever. I like to live on higher plane than the elementary school route you have adopted. Unlike yourself, I don't engage in turd-think or feel the need to seek a turd consensus to feel validated.
You really ought to work on that thin skin.
Hey OldHouseFan,
For what it's worth, I think I got it. I bet others did too. Of course it's hard not to take things personally and maybe this thread wasn't as good a candidate for your comments as http://forums.taunton.com/tp-breaktime/messages?msg=58865.1., but I think you point had merit.
Now then, apologies if I contributed to hijacking this thread.
-Don
Thanks. Yes, it was a carry-over from that thread in the sense that it was still fresh in my mind when I read the post in this thread.
I don't really care, and it's none of my business, if someone comes here and says "I just bought a hammer thingy, how do I use it?" I was simply using the post as an illustration of what I thought might be frustrating or annoying - given the exchange in the other thread.
Being that I DIDN'T want it to be taken personally, I put in the disclaimer.
Bill, Thanks for taking the time to answer.
Here is the rest of the info you require:
1. I don't need a building permit if my structure is under 107 sq ft.
2. The site has a fair amount of slope to it (about 30" over 10 feet) but I'm going to level it and retain it with concrete retaining wall blocks, so the site will be level. Once the sod and topsoil are removed, the base will be very sandy with very good drainage.
3. Storage: Nothing heavier than my snowblower.
I'll have the retaining wall installed before I set the forms for the pad, that's why I was asking about the gravel. I would also like to make a sloped concrete ramp at the doorway once the pad is complete. BTW, the ground pretty much levels out on the side the door is on (front). The retaining wall will be on the back and taper to ground level on both sides with about 2 feet of space all around the building.
Thanks again.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
Patrick,
Gravel base; 6". first compact the soil under the gravel, lay the gravel, then compact the gravel. Use a jumping jack type compactor.
Forms 2x8!?!? I'ld use 2x4 for that little thang, maybe with the edges 4-6" deeper by 6"-8" wide.
Rebar? Only in the thickened edges. If that.
Ramp: Excavate the ramp area when excavating the slab. Compact and add gravel. Slope the gravel out to 3 1/2" under the lawn grade. Add sloped 2x4 forms from the slab form down to flush with the lawn. Rebar (?) around the edge, with the two side pieces extending 12" into the slab. Add 1 or 2 24" pieces across the ramp to slab junction. <= 24" OC. 1" from the surface of the 'crete, 3" from the edges.
If you use adobes for rebar chairs, soak 'em in water 10 mins and set them the last thing before pouring.
Pour the concrete as stiff as you can work and/or add plastisizer. As soon as you've finished the surface and it has set up, wet the 'crete and keep it wet for 7 days.
SamT
Thanks for the info Sam. I think I'll use 2x6s for the form that way I can go deeper at the edges. I understand (and like )your idea about the ramp and reinforcing it with the slab.
Cheers, P.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
can u get a concrete truck in there?stake the dickens out of the forms
bobl Volo, non valeo
Baloney detecter
I doubt it. I'll be about 50' from the front of my garage.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
some of the masoary suppliers around here (NE) sell concrete by the yard, you get it in a trailer (thiers)my guess is you will only need a couple yards, so this might work out well, unless you have hot weather.
bobl Volo, non valeo
Baloney detecter
Have you worked out the number of bags of concrete?
If the concrete mixer can't get to the slab, you still might arrange to have one come to the property and get 2-3 friends and 2-3 wheel-barrows to ferry it to the forms. It'll will be quick, might be cheapest, and will keep you from wearing most of it mixing it with a shovel. Should be available in KW...
Patrick,
Leave it to me to suggest you re-examine your project, LOL....
Question: Why are you determined to set this garden shed on a concrete slab? You said it's a pre-fab; does that mean it's got no floor?
What I'd do in your situation is grade the area to rough level, then set eight concrete blocks (two for each corner of the shed) and level those. Then build a wood-framed floor with doubled rim joists, decked over with ¾" ply, sitting on the concrete blocks. Have the shed delivery guy drop the shed onto the floor, lag-bolt it down through the sole plates, and you're done. Probably cost you a third as much, take 1/7th as long, and work just as well. And you can build a wood ramp husky enough to handle your snowblower out of 2x6 laid flat.
Here's a photo of a custom shed I build for a client; the floor is framed just as I told you. We built this one about 4 or 5 years ago; the shed hasn't settled or moved a millimeter since....
View Image
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Nice shed Dino!
At my previous house, I built a shed using a technique similar to yours. I realize that the way I'm going is a lot more work and expense but this is the way I want it. Personally, I think that the concrete slab and ramp is a little cleaner looking and will never have to be touched again. I'm also having interlock installed that will butt up cleanly to the ramp. I'm also interested in learning a little more about working with concrete so I have an ulterior motive. I'm sure I'll regret it though because of the time it will take.
Thanks for the help,
P.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
Using your imagination is also an approach, e.g.
1.Pieces of broken sidewalk (lotsa places love to give that stuff away, even delivered) laid out right on the dirt and the cracks filled in, soup up the dirt with water first for a firm base, plenty good for a shed.
2. Old computer room floor - got a couple hundred sq feet of this stuff in 2 ft squares once free, lay'em on dirt, tack weld the joint, nice tiled floor ready to go.
3. Plain old compacted dirt - in Illinois, this was Pops old favorite, fine if kept dry, I left a dirt floor in my barn where some blacksmithing is done, sparks dont go skittering off across the floor, just die where they land.
4. Dino already showed option 4.
5. Used torn off roofing - made one of my back driveways out of this, but labor intensive pulling all the nails first.
6. brick or paving blocks may be best for your case.
etc.
For a slab this size, you can avoid the cost of renting a jumping jack by using a 4x4 post with a scrap of ply nailed to the bottom.
Avoid using U-cart concrete. It tends to settle during driving, leaving the aggregate on the bottom of the cart and the water on the top. It's not fun to try to get it to flow out the chute.
If you can rent some two-wheel wheelbarrows, they don't tip over as easily.
FWIW, I'm a 'regular' who can be critical, but I didn't jump your case for a couple of reasons. You came in with a pretty good idea of what you wanted to do, it's a size that would be a good learning experience, and you asked several direct clear questions. I don't have a problem with this type of question at all. But i do have a problem with people who respond that yopu should do your research elsewhere before posting here.
I'm sorry, I thought you wanted it done the right way.
Hi Ed,
That's a good point about the U-cart 'crete as I can imagine it would be a pain getting the aggregate re-distributed.
I live in an new area with a fair amount of new construction so I "may" get lucky and find some guys pouring with some left over at the end of the day. Thanks for your patience as well.
P.
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
On the left-over concrete ... you need to ready to act fast. If it's left over from a pour, it's been in the truck for a while and you won't have much time to round up a crew. Maybe be proactive ... go to a house being built, see if they have a need for a small pour, maybe a sidewalk, and ask if you can add a yard or two to the order. Sometimes the builder is waiting to order concrete until he can get a big enough order to warrant the truck, and your extra 2 yards might make the difference.
Also, there might not be enough left-over concrete to do your slab. If so, have a couple of 2x4's and stakes handy that you can use as a divider to make the slab smaller. maybe you'll have to do the slab in 2-3 small pours, but the price might be right enough to justify it.
I'm sorry, I thought you wanted it done the right way.
Edited 6/4/2005 7:40 pm ET by Ed Hilton
You said that you had a trowel . Is it a rectangle steel ,mag or wood? If you are going to learn flat work go watch a crew some time ,and ask a few questions but don't make a pest . Then get a mag or wood float and a large steel . I like the magnesiun float better than wood. In fact get two of each and have the kid learn also . If you have never done this and it gets hot even a little help will be a godsend.
I like to run the steel in a large arc , arm streached as far as i can . keep the steel as level as practical. With the leading edge above the concrete. This is one of the things to watch the pros do before you try on your own.
Personally, I think that the concrete slab and ramp is a little cleaner looking and will never have to be touched again.
I can't see the cleaner look myself, but taste is a personal thing and you're as entitled to yours as I am to mine, LOL. The skirt lattice I used on that cabin in the photo is not the only option, just what the client there asked for. You could also lay a complete perimeter of concrete block on a compacted base of gravel and rock dust, then stucco the outside face and leave it visible under the shed. Or, even easier (and less subject to cracking), you could TapCon a skirt board of plywood to the eight corner blocks in the original proposition and then stucco over that using diamond lathe etc. Lots of different ways to approach it....
I'm also having interlock installed that will butt up cleanly to the ramp.
I can't quite follow you about the 'interlock' here??
I'm also interested in learning a little more about working with concrete so I have an ulterior motive.
For an ulterior motive like that, I am with you no problem. I've frequently done similar things. I like to tell my customers that I've made all my learning mistakes working on my own house, LOL....
I'm sure I'll regret it though because of the time it will take.
I tend to agree you may eventually regret a decision to do this with a full slab as you propose, but for different reasons.
Given your climate--similar to mine here in Québec--you will have severe freeze-thaw cycles in the ground under that shed, so if you don't build the slab to basically the same specs as you would have to do for a house, it's gonna crack and heave sooner rather than later. This means you really ought to be putting down footings and frost walls to below the frost line. Here, that's 60" down. I don't know what it is at your place, but it's gotta be a minimum of 36" and possibly 48". That's a lot of excavation work, forming, concrete, and gravel. I don't know anybody willing to spend that much on the foundation for a snowblower shed.
OTOH, if you skip all that work and expense and pour a slab on grade, unless your substrate is well layered and compacted, and sufficiently deep to either get below the frost line or to 'absorb' frost heave, your slab is going to crack in a year or three, possibly severely. (All concrete cracks eventually, anyway.)
A wood frame floor set on concrete blocks will flex and move with the seasonal ground movement and you'll never notice it happening because there's no crackable finish work inside (gyprock, for instance) to reveal how much the frame has worked. In the spring, all will look as it did the fall before.
Just my point of view....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Well just to give you another opinion, I'll answer your Qs directly:
1) Substrate?: I'd fill the flat area you build up behind your retaining wall with stone (gravel). Minimum depth 6". The type you proposed is probably OK, but normally ~1" washed stone is used for that application. Don't put any fill dirt under it at all. Washed stone is pretty much self compacting. The stuff you are talking about could probably be compacted with a hand tamper as long is it is installed in thin lifts - maybe 2" per lift (layer). Renting a mechanical tamper would be overkill.
2) Slab thickness?: ~ 4" is plenty think for the pad. I'd form up with 2x4s. If you really want to thicken the edges - OK, but it is not necessary. This slab will see the lightest duty use just about any slab will.
3) Rebar?: You don't need steel. If you really wanted to add some, I'd just put a single piece of #4 around the perimeter. (#4 means 1/2" rebar - the #4 means 4 eights). Wouldn't cost much.
4) How difficult?: If you want to learn to finish concrete, this is the perfect project. Since you said you are reasonably "handy" you will be fine - unless you are lying ;-). It's small enough that you can screed across your forms with a 10' board. (It's 8'x12' - right?)
First, you have to order that amount of concrete from a ready mix company: mixing it by hand, even with a mixer will be a big mistake. Plan on using wheelbarrows to transport the concrete from the street to your project location. Get a helper. Wheeling 1.5 yards of concrete will be hard work for about a half hour. Order 2500 or 3000 PSI mix with fiber mesh, 4" slump, and tell the concrete dispatcher that you will be hand wheeling it so you won't have to listen to any "verbiag" from an impatient driver. I hope the wheel trim is downhill ;-) . Use "contractor sized" wheelbarrows, and don't let the driver fill them up all the way. A full wheelbarrow is a bit difficult to manage unless you are a 300# linebacker. Use a shovel and a garden rake to move the concrete around in the forms. Concrete guys use something called a "come along" but you can get by with out it. Once you get your forms filled up, screed it out with your 10' straight board, having your helper to "drive" the other end. the idea is just to get the concrete to the (flat) had have the surface rocks pushed down a bit, but not to necessarily produce a smooth finish at this point. Don't play with the wet mix too much. It makes the water come to the top, which results in a weaker surface. Send your helper home after that. Have 2 pieces of plywood ~12" x 18" so you can kneel on the concrete without leaving knee impressions. In 1 to 3 hours, time depending on weather, etc, finish the concrete. You will see the bleed water come to the surface, and then start to dry up. It takes experience to know "when" but a simple test is to wait until you can press your thumb in it and leave an impression without getting wet concrete on your thumb. For a beginner, start finishing with a wood float, and then go back over with a steel one if you want a slick finish. Slick finishes are easier to clean (sweep), but can be slippery when wet, but I'd say slick is the normal finish for a shed. If you want to broom it for a rougher finish, use push broom. The coarser the broom, the rougher the surface. Wet the broom first - as a matter of fact, wet all your tools first. It keeps the concrete from sticking to your tolls. Broom finishes hide a lot of sins ;-).
Lastly, have fun with it! You could build a PT wood floor system, but then you probably would not learn much of anything. Or at least cost out doing it either way, and report back to us as to your findings.
Hi Matt.
Thanks for the tip on the retaining wall. I built 2 large unilock planters, a patio, and a walkway at my last home using the mfgs recommended installation instructions and after 10 years, they looked as good as new. As far as being handy. I've done a ton of carpentry over the years just never any cement work. For example, I built a 700 sq foot, 4 level IPE deck last year, just my 13 yr old son and I.
I've read some articles on this subject but the more I research, the more confused I get (just read the difference of opinions in this thread) but I'll always take the long road if that means doing it right.
I'm defiantly going to look into getting pre-mix. Thanks for the specs :)
I have a lg contractor WB and one smaller one so my son and I should be able to handle it. I know how heavy it is.. I mixed 60 bags by hand last summer for my deck piers. I can handle about 2 bags worth and the grade is in my favour :)
I'm going put a 6" compacted gravel base throughout the excavated area. That way I can build up the retaining wall base at the same time. I'll back fill the wall with gravel and filter cloth as the mfg recommends. (the wall is only about 24-30" at it's highest)
Then I can form the pad and ramp. I did see a video on this and they used a heavy wire mesh in place of the re-bar. Any comments on that? Otherwise I'll just use a little re-bar around the edge and where the ramp meets the pad.
And to everyone else, thanks for your helpful input!
A fanatic is one who can't change his mind and won't change the subject.
Sir Winston Churchill
couple thoughts on the ready mixmay have to pay a surcharge for a small load (<5 yds)don't forget to have a good ramps to get that 600 lb wheel barrow full of concrete into you form.a small pump is an expensive option for moving that much concrete (no, not a big truck, a pull behind, about the size of a compressor they use to jack hammer streets)to repeat myself, if it's hot. don't be suprised id the stuff drys fasr
(speaking from experience)
bobl Volo, non valeo
Baloney detecter