I poured a monolithic slab for my 24x30 workshop/garage in SoCal. No sill wall. Footing is ~12-18" wide and ~18-24" deep.

 

I am not sure what you mean by a sill wall. The foundation wall is usually called a frost wall in New England, however in other parts of the country a slab is often placed with a turned down edge which might be as little as 12 or 18 inches deep. The other design, specifically a footing with a stem wall, is generally used for the basement, not often used for a detached garage.

As for the pour, well you can pour the entire combination of footing, wall and slab monolithically if you choose, but more often the slab is poured separately, since the slab for a garage typically has no structural function, it is just there to provide a suitable surface to park your car on. The slab is normally designed with crack control joints, and in my experience is usually not tied to the frost wall at all.

 

Depicted below is a monolithic slab - and is how my slab in the pictures was poured. I have done both monolithic slabs and stem walls with the floor poured inside the stem walls.

I think what the OP is referring to as a sill wall would be the portion of a stem wall construct that would extend above the garage floor level - and the walls are built upon (OP, please correct me if am wrong). I have never seen a monolithic slab with an integrated "sill" wall, but I guess it could be done with the appropriate form work.

A height advantage can be had using the stem wall construction - in that the walls are thus higher from sitting on the stem wall and allowing more overall overhead clearance and room for a taller garage door. With 8' and taller garage doors becoming more the norm this can be a factor. Of course wood framed 9' or taller walls could be erected on a monolithic slab to accomplish this.

 

I think what the OP is referring to as a sill wall would be the portion of a stem wall construct that would extend above the garage floor level - and the walls are built upon (OP, please correct me if am wrong). I have never seen a monolithic slab with an integrated "sill" wall, but I guess it could be done with the appropriate form work.

Most every garage slab we do has a concrete curb poured with the slab for two main reasons: It keeps the plate higher & away from potential water & allows the slab to be pitched to the OH doors while the curb is tapered to allow the wall to be built on a level surface. It does involve mor ecomplex forming & finishing, but it's still fairly easy to do. I believe this was covered a while ago, a few pics may even be in that thread.

BTW vsheetz, is that colored concrete or is it just decieving in the pic where your pouring it?

 

Slab dimensions we use around here:

Rebar mat in the middle of the slab extends to within an inch of the outer perimeter. Two bars centred in the thickened footing and a single bar in the curb. Add Fibermesh and you should be good to go.

Typicial method for hanging the inside form without pins to support it.

Notice that for the drawing purposes that the gusset is shown at the top of the curb. Leave enough space there to slip a trowel under it. Anchor bolts are placed as per usual layout for your area, although you might want to use longer ones so they sit down into the footing at the thickened edge.

 

Thank you so much for the drawing, I am printing it out and going in my notes.

great design, I see you have the plywood guesset on the back side and I assume you use gussets on top of the 2 x material to hold it together.

I like the angled design so you can get a trowel in there to finish as normal.

You have never had problems with the 2 x material that is cut an angle ever pushing out towards the slab? with not takes or anything holding it up???

Thanks again,
Mike

 

The concrete for my 24' x 36' shop was poured in '96 and the concrete man used the form which "jlhaslip" has shown. He used bolts to hold the forms in place for the 6" high wall he was pouring on mine, with the bolt being easily removed after the pour had set most of the day. I asked for this at the time as I had plans to just "wash out" my garage floor with a garden hose. Well, after it became more of a "storage building" for my wife and son :yes: I haven't washed it out since. As a matter of fact, I haven't been able to use it for it's intended purpose much. If anyone come up with a design for a garage/shop which will deter family members from using it as a storage building--please advise me of these plans. Thanks, David

 

Nope.

Make them out of 3/4 ply and leave about 6 inches of meat on the top and sides seems to work. Place one about every 3 or 4 feet on the outside wall. If in doubt, or using plywood for the inside form, add extras and reduce the spacing of them.

Use 2 x 2's to nail them to the inner/outer forms.

You can also look at additional support by using blocks across the top of the 2 x material.

As for bulging and wall deformation, that is why the wall is 5" wide only. With 1/2 " ply outside and 1/2" drywall inside of a 2 x 6 frame wall, the concrete can move a little and the wall can still sit where it needs to.

Of course, we don't need any earthquake or termite protection around here, so I am not familiar with any implications those conditions might bring into the equation.

I've built 30 ' x 40 ' shop slabs using this method and it was all good.

 

Great thanks again for the advice. I am excited to give it a shot. I will keep everyone informed once the project starts....Gonna be a while though I think at this point

 

If anyone come up with a design for a garage/shop which will deter family members from using it as a storage building--please advise me of these plans.

Hang an overhead door on the thing, but don't wind the springs. Works for me.

 

Haha...I will second this.

 

Everyone new to concrete work thinks 'monolithic'. Be smart, and break this rather overwhelming (for a beginner) task into several stages. You will be glad if you do... and you will regret it if you don't.

The 'exploded' picture shows the most realistic way to tackle the job.

BTW...... Keep ALL rebar at least 2" away from the forms and the edges of the slab.... everywhere.

 

Good Point.

I am not sure yet, but realistically I am going to build the forms with a couple buddies and the finish work I will sub out.

In your experience and some one with out a ton of skill in concrete that if I were to sub out the finish work of the monolthically filled foundation that a novious can handle the 16 x 20 garage.

or

would you still recommend breaking it up.

If you break it up would you do the foundation and sill wall in one shot and the slab in another or break it up into three parts???'

Thanks
Mike

 

Doing the footing is not rocket science, and it requires no real skill. Basically, you dig a clean trench, install the rebar on wire 'chairs', and then pour it to a specific level. I can't tell you the thousands of feet of footings I've done by simply dragging and wiggling the backside of a flat shovel along like a boat.

The wall is next. You probably would want to hire a mason and a helper to do this for you. It needs to be straight, level, and smooth. Difficult for a novice to do.

You can install all the expansion joint yourself in a few hours. It simply nails into the wall with 'stub' nails.

You can also pour the wall yourself. No biggie here at all. Just order 'grout' mix, and not regular concrete for this. (That's important... they set up and cure differently)

Yes, by all means have a pro do your slab pouring and finishing..... although you can handle the slab prep yourself.

That's all there is to it. Of course you will have to learn the proper and legal ways to do some of this work, but that isn't hard. And everyone here will help.

So..............

1.- Dig trench
2.- Install rebar
3.- Pour footing concrete
4.- Lay block wall
5.- Fill block wall with 'grout'
6.- Nail on the expansion joint
7.- Prepare the slab (include all under-slab wiring and piping)
8.- Pour & Finish the slab

There are a few exact steps to follow in doing some of the things above, but that's the outline in a nutshell.

 

Well thanks everyone for the advice.

A lot to think about, have a few months to think about it.

Great advice and a few choices.

I will take pictures once the project starts and keep things going

 

May I suggest that now is the ideal time to do the most time consuming part of the job. And that is compiling and learning all the required knowledge and information. Your comment about "I will take pictures once the project starts and keep things going " is a little disturbing. Why? Because that's how most novices get themselves into deep trouble.

Just as we contractors do, you should have every single step of this project (and they are ALL projects) laid out clearly in your head as well as on paper. It is often too late once you've started to get workable answers. "Should haves and Could haves" hurt both the pride and the pocket book.

 

Hey valid point and i 100% agree to with you, i was not real clear but i am taking this time to make re make and finalize a game plan and budget for the whole project. I think i am atleast 14 months out right now. What i meant but thinking was figuring out what type of foundation and panel i want. Eith the pictures i meant once i start the project i will post pictures of the progress of the garage

 

WillyT,

That's a great drawing. Thanks for sharing. Does anyone know if it's drastically less expensive to build the stem wall with concrete blocks and then pouring them solid, vs. building forms and using poured concrete? Let's assume with a block wall, I'd build it myself, and with a poured wall, I'd hire the same guy doing the slab pour.

The former seems easier for DIY, but I'm not sure which method would yield a stronger wall and whether the cost differential makes it worth doing it myself. Thoughts?

 

Thats a great question, I would like to add one thing on to it or one question to help expand.

I am not a foundation expert so please work with me here, I know there are 6'' 8'' 10'' 12'' and maybe larger and there is normal weight light weight, blocks for bond beams with rebar some use mesh between the rows.

I feel pretty confident to assume that there is different in how much weight each can handle and also the shear strength of each block.

For my situation, I am building a 16 x 20 garage but would it be different for a larger garage or a basement on a house or a basement with a two story house on top.

What I am getting at, is how do you know when to expand and to make TitaniumVT question more specific can you relate it to a 16 x 20 garage?

thanks,
mike

 

Stay cognizant of the fact that lightweight blocks should not even be considered when you are contemplating placing the load of an entire structure upon them. Use regular concrete blocks.

Next, concrete isn't cheap. And you are anticipating filling the entire 8" width of that 'formed' wall with the stuff. Filling only the cells in a block wall will require much less grout. (and 'grout' mix may be cheaper... I'm not sure) You could fill that block wall I drew in post #15 with only 3/4 of a cubic yard of grout... It would take about twice that much concrete to fill a wooden form of the same size.

Now you come to the cost difference in nothing but some blocks and mortar to make a wall, compared to buying, cutting, and fitting all the necessary 3/4" plywood, 2x4's, and nails for the necessary formwork to make a solid concrete wall. Remember, you're doing two sides to this formwork. Then, of course, you do have to know a fair amount of exactly how those forms are to be constructed. 3/4 plywood ain't cheap, and it's going to take a heap of 2x4's for "whalers" or more correctly, 'wailers', (lateral reinforcement), stiff backs, (vertical reinforcement), and diagonal bracing and anchor stakes to keep the formwork straight and plumb. Then you have the cost of "spreader ties" to keep the internal size of the form consistent to be considered. Formed walls also require more rebar than filled block walls.

Blocks ARE a 'form' in themselves. And all you do is pour them full of grout. No plywood, no bracing, no disassembly of the form afterward (you should not leave the wood in there) I honestly would recommend blocks as the better way to go for a simple structure like a garage.

Strength: I've built several hundred two-story houses on block foundation walls. Although only a few that way with basements. We really do very few basements here in Florida.

 

Stay cognizant of the fact that lightweight blocks should not even be considered when you are contemplating placing the load of an entire structure upon them. Use regular concrete blocks.

Next, concrete isn't cheap. And you are anticipating filling the entire 8" width of that 'formed' wall with the stuff. Filling only the cells in a block wall will require much less grout. (and 'grout' mix may be cheaper... I'm not sure)

Now you come to the cost difference in nothing but some blocks and mortar to make a wall, compared to buying, cutting, and fitting all the necessary 3/4" plywood, 2x4's, and nails for the necessary formwork to make a solid concrete wall. Remember, you're doing two sides to this formwork. Then, of course, you do have to know a fair amount of exactly how those forms are to be constructed. 3/4 plywood ain't cheap, and it's going to take a heap of 2x4's for "whalers" or more correctly, 'wailers', (lateral reinforcement), stiff backs, (vertical reinforcement), and diagonal bracing and anchor stakes to keep the formwork straight and plumb. Then you have the cost of "spreader ties" to keep the internal size of the form consistent to be considered. Formed walls also require more rebar than filled block walls.

Blocks ARE a 'form' in themselves. And all you do is pour them full of grout. No plywood, no bracing, no disassembly of the form afterward (you should not leave the wood in there) I honestly would recommend blocks as the better way to go for a simple structure like a garage.

Strength: I've built several hundred two-story houses on block foundation walls. Although only a few that way with basements. We really do very few basements here in Florida.

Valid Point

A couple questions to expand on the block foundation.

For a 16 x 20 garage what size block would you use in Florida?

Do you guys use "bond beams" - but my terminology may be off there but they have a slot cut out the bottom so you lay a horizontal piece of rebar or do you use the wire mesh?

Mike

 

Here is what we call a "Header Block". Other places may call it something different. A slab done this way is not the same as the purely "floating" slab shown in my previously posted drawing. This one locks into the block wall all around, and you then build on top of the slab.

The other drawing is designed to run a wall straight up past where the slab will end up. So you just butt the slab into the 'stem wall'. I prefer the way shown below.

 

Here is what we call a "Header Block". Other places may call it something different.

So this is a way to tie the slab and the block together.

Because you have concrete on masonry do you need to put a buffer between the two like when you put a foam between sidewalk and a concrete slab?

The other question is for this garage I would like to have a 6'' high stem wall 6'' high when doing a concrete filled wall it was going to be 6'' wide.

Instead of using this header block do you use just a normal block up 6'' above Finished Floor?

What program did you use to draw that? That is awesome and really detailed.

What size block do you guys use in Florida?

Thanks again,
Mike

 

One thing to keep in mind on these little drawings is that there is normally rebar running all the way from the footing, on up through the stem wall, through the slab, on through the full height walls... right up to tie in with the bond beam at the top extent of your building walls. I'm not showing any of it because it is a pain to draw, and it clutters up the drawing.

 

Willie T, you are a master with Sketchup! Thanks for all of the great insight. Two final questions from my end:

1. Is there any bracing of the blocks horizontally (i.e., anything comparable to the horizontal runs of rebar you'd use for a poured concrete stem wall)? Maybe it's not necessary. I only ask, since that support seems to be lacking with this approach

2. Would you have any concerns using blocks like these for stem walls in an earthquake zone? I live in Seattle, and while we don't get many earthquakes (the last one of any significance happened in 2001), we are technically in an earthquake area. I hardly ever see block foundations around here, but have no idea if there's a good reason for that, or if it's just that builders aren't used to this technique.

Thanks again. You guys are awesome.

 

Most of this will come down to a local building department decision. They are your definitive and final answer for things structural.

 

Going off the premise that I were to do my foundation with a 8 x 8 x 16 normal weight block, is there any tricks or calculations you guys would recommend in figuring out many blocks would be needed???

 

Sounds like it is about 113 - 8 x 8 x 16 block per 100 sq feet of wall? Can anyone confirm this.

I have also found that you want about 7.5 cubic feet or mortar per 100 blocks used - can someone confirm this too???

If i were to get the mortar bagged should I be looking at Type S Mortar in a foundation setting?

Can anyone elaborate on what a grout mix is and why you would not use normal 2500 psi concrete???

 

Right on, on the blocks. I'd say a little light on the mortar.

With grout vs concrete, it's a water content and mixture ratio thing. Concrete, as it cures, tends to actually shrink a little. This leaves you with a less than desirable tight bracing inside the blocks. Sounds nuts, but that tiny, tiny space left between the blocks and the hardened concrete core costs you a lot in reinforcing column strength. I don't know the details right off the top of my head, but I learned many years ago from commercial work that you really don't want to pour the wrong stuff in the wrong place.

Simply put, concrete loses strength when it's made soupy enough to flow as it needs to in "grouting" work. Grout, on the other hand is mixed to account for and to anticipate the water absorbing properties of masonry units (blocks), and it hardens the way it is supposed to inside block cells.

Unfortunately, most of today's concrete guys would give you a vacant stare if you asked them about this sort of thing. Kind of like the way they will also tell you "Concrete will get cracks... nuttin ya kin do about it." But ask them why the sixty year old slab in your father's garage has never cracked, and they will again get the stare. A lot of skill and quality has been lost in many of the trades over the decades. But I guess that's progress. :no:

 

Right on on the blocks. I'd say a little light on the mortar.

With grout vs concrete, it's a water content and mixture ratio thing. Concrete, as it cures, tends to actually shrink a little. This leaves you with a less than desirable tight bracing inside the blocks. Sounds nuts, but that tiny, tiny space left between the blocks and the hardened concrete core costs you a lot in reinforcing column strength. I don't know the details right off the top of my head, but I learned many years ago from commercial work that you really don't want to pour the wrong stuff in the wrong place.

Of course, most of today's concrete guys would give you a vacant stare if you asked them about this sort of thing. Kind of like the way they will also tell you "Concrete will get cracks... nuttin ya kin do about it." But ask them why the sixty year old slab in your father's garage has never cracked, and they will again get the stare. A lot of skill and quality has been lost in many of the trades over the decades. But I guess that's progress. :no:

Well hopefully with sights like this knowledge and I mean good knowledge can transpond through out the generations and us (younger folks) can learn.

Thanks for the site about mortar wanted to ask one other question to ya about the block foundation, what size or dimension do you guys use down in Florida, to give some reference to what I would should be doing out here. Like you said though the building dept. of my county will be making the final call.

Anyone else with there footing sizes too, please shoot them out.

 

Yes, Type S is suitable for below grade work.

HERE is some good information about mortar.

 

We usually run a 12" high by 16" wide footing for a garage like you're talking about. We go down around two to three feet because we have no frost line to worry about.

It's working on midnight here, and I still have to walk the dog.

Catch ya later.

 

thanks for the knowledge, looking to keep the footings about like you described.

enjoy walking the dog

thanks again mike

 

Just a thought as I didn't see it mentioned, the height of a block wall will allow you to use 2x4x8 wall studs (if they apply in your height requirement) Vs longer studs.

Here in the mid-west we need to go below frost line so it's footer, then block, then floor.

Willie T, Very good info. :thumbsup:

 

I thought I'd introduce the first step in laying out your garage. (Well, it's actually the third step, but more about that later.)

The small triangle measurements help you get the lines started in more or less the correct orientation.

The cross measurements on the large rectangle are what you will use to check for accuracy. Slight increases in one measurement will be echoed by reductions in the dimension for the other diagonal. Playing with the relative measurements is how you get the rectangle square.

And it HAS to be EXACTLY square. An eighth of an inch off is NOT acceptable.

The second picture is how you locate your "Batter Boards". These are what you will attach your string lines to for the really accurate layout.

 

Thanks for the more information and the pictures to help visualize everything.

Something we can all benefit from too.

 

You are going to hear and read a lot about how you will need to go out and buy a laser level to get accurate elevations. Or at least get a "Builder's Level" (the scope on a tripod). They will say you cannot have true accuracy without them.

Neither of those statements is true.

Think about it. The Egyptians with their pyramids... The Greeks and Romans with all their aqueducts, roads and coliseums... The Mayan and Inca Indians.. and even our own forefathers... had nothing like that. They used water levels and plumb bobs. I have, too. And so can you.

In fact, though almost any of today's builders will want to dispute this, the water level is actually the most accurate of any of the tools I've mentioned.

So, unless you have too much money lying around, or just like to buy yourself new toys, you can lay out every part of this garage with those two 'old fashioned' tools, and a wooden, bubble type hand level.

CLICK HERE for a link to making and using a water level. You can GOOGLE for a lot more. I personally have a manufactured one that has a built-in sliding tape measure so I can just use math instead of moving the end of the water level up and down... but either way works equally well.

 

I agree water can not lie, not matter what it will read true.

I do have a Topcon ATG6

Helped some family friends reside there house and two sheds from T-11 to hardie and they bought the builders level to help get the hardie lined up from the get go. At the end they gave it to me as a thank you.

I donated my labor, nail gun and air compressor.

I do have a water level too, all my dad and grandpa use

 

Normally 2x's are used especially on the outside. But 3/4 ply would work. Use more gussets to maintain a straight curb.