[n0c7]

I'm going to be building a 20x22 detached garage with 9ft ceilings on a concrete pad that was poured ground level with no curb. I believe the pad is sloped by 2 inches for drainage towards the front.

I'm thinking of building the rear wall(highest point) first to 9ft and leveling then fastening it, then building the two side walls level with the studs gradually increasing in size to make up for the 2" slope, then finally finishing with the front wall with the garage door opening.

Couple of questions:

1) Is starting at the back wall highest point and building to 9ft the right place to start? This will effectively make the front walls 9ft 2in by the time I get there. This makes more sense to me than starting at the front and having the back wall 8ft 10in.

2) In the event one of the side walls is slightly higher or lower than the other, which should I build first? The lower of the two makes sense in my head.

 

[firehawkmph]

n0,
It's probably easier to build the tall wall first. Finish height just depends on what you want to end up with. My question would be does your slab have a footer under it? With no curb, I would not frame right on top. Around here, we usually go a couple courses of 8" tall block to get the wood up above grade so it doesn't draw moisture and rot.
Mike Hawkins

 

[Bondo]

I'm going to be building a 20x22 detached garage with 9ft ceilings on a concrete pad that was poured ground level with no curb. I believe the pad is sloped by 2 inches for drainage towards the front.

I'm thinking of building the rear wall(highest point) first to 9ft and leveling then fastening it, then building the two side walls level with the studs gradually increasing in size to make up for the 2" slope, then finally finishing with the front wall with the garage door opening.

Couple of questions:

1) Is starting at the back wall highest point and building to 9ft the right place to start? This will effectively make the front walls 9ft 2in by the time I get there. This makes more sense to me than starting at the front and having the back wall 8ft 10in.

2) In the event one of the side walls is slightly higher or lower than the other, which should I build first? The lower of the two makes sense in my head.

Ayuh,... Donno who pours pitched slabs,...

The wall areas shoulda been poured level, 'n the pitch built into Just the floor area...

Regardless, you have to KNOW where the pitch is, before ya start...
Get a sight level, 'n set up string lines to measure from to find Level...

 

[jagans]

Its a patio, not a proper foundation to support walls. You need a proper foundation to build a garage. The slope is built into the slab, Read my signature.

 

[hand drive]

pick your stud size and frame the tall wall first. then cut the studs as you go up hill. if you want the back wall 9' you will need 10' studs for the rest of the structure even though they will only be cut up to 2" taller than 9'. better to figure 9' for the tall wall and 8'-10" for the back wall and use 105" studs for the whole thing...

 

[joecaption]

Sounds like a sure way to have rotten siding, cracking the slap on the outsides and water coming in under the walls.
I know around here we have to do a stem wall, no just building on top of a slab with no footing.

 

[n0c7]

It's interesting how some of the builders pour them out here. Mine is actually graded very high up, actually to the same height as the neighbor who has a curb built into his slab.

I personally don't like it however the way they get around it here is by using pressure treated sill plates, a gasket under the sill plate, vinyl siding on the outside, and sealed treated OSB sheeting. I had the same concerns most of you mentioned however 10 years ago we had built one similar to this and the only issue was the MDF trim used around the door which wicked up water and rotted. I see most builders using aluminum flashing instead now to avoid htis.

 

[n0c7]

n0,
It's probably easier to build the tall wall first. Finish height just depends on what you want to end up with. My question would be does your slab have a footer under it? With no curb, I would not frame right on top. Around here, we usually go a couple courses of 8" tall block to get the wood up above grade so it doesn't draw moisture and rot.
Mike Hawkins

I didn't see it poured as we bought the house as spec but as far as I now it's adequate to hold a garage up. Regarding the 8" blocks - do you have winter where you live? I would be concerned with the frost they would move too much here.

 

[n0c7]

Its a patio, not a proper foundation to support walls. You need a proper foundation to build a garage. The slope is built into the slab, Read my signature.

I always wanted a BBQ in the garage.

 

[firehawkmph]

I didn't see it poured as we bought the house as spec but as far as I now it's adequate to hold a garage up. Regarding the 8" blocks - do you have winter where you live? I would be concerned with the frost they would move too much here.

Yes we have winter in Ohio, snowing right now and about 20 degrees F. As far as the block lifting, that's what the footings are for. We generally go 44" deep for garage footing around here. Then the block is laid up and tied to the footings with rebar. Normally two blocks above grade. Then the inside area which has been stripped of topsoil, is given at least a 4" base of compacted #57 limestone. Next a .006 mil layer of visqueen is laid on top, followed by 4"+ of concrete with wire mesh laid in. Makes for a solid foundation, keeps the wood up out of the snow and the wet. We too use treated sill plates and treated bottom plates on top of that. The main thing is keeping the wood out of the snow. Here's some pics of a typical garage foundation here in Ohio.
Mike Hawkins

 

[firehawkmph]

One other idea, and I'm guessing you probably don't want to hear this, but anyway. You could have somebody with a compact tractor/backhoe with a 9" wide bucket, trench an area around the slab you have now, right up against it. Then pour a trench footing up to within one block below grade. Insert pieces of rebar in the footer so it goes down all the way and sticks up around 16" on 4' centers. Lay three rows of block and fill the cores where the rebar is solid. Walls will end up all the same level (with a decent bricklayer) and you'll have a solid foundation for your building. I know it sounds like a lot, but in the whole scheme of things, it really isn't.
Mike Hawkins

 

[n0c7]

This topic went way out of line. Constructing a detached building on a ground level slab has been practiced here for decades, it's not going to fall down in any short order or even cause problems if precautionary measures are taken and by the time it does the stability of the house will be much more questionable and of a concern at that time. This is what I have to work with, I'm not ripping out a $10,000 slab. I have my opinions too - why pour concrete only to fasten down cheap wood? The walls should be formed out of concrete and them diamond coated. Let's finish it off with some gold paint while we're at and maybe the queen will visit.

So back to my original questions, any other takers?

 

[kwikfishron]

Build your front and back walls at whatever height you want first, then pull a string between them and frame the sloped walls to that string.

 

[n0c7]

Build your front and back walls at whatever height you want first, then pull a string between them and frame the sloped walls to that string.

Pretty much what I had visualized in my head. Thanks!

 

[Hardway]

n0,
It's probably easier to build the tall wall first. Finish height just depends on what you want to end up with. My question would be does your slab have a footer under it? With no curb, I would not frame right on top. Around here, we usually go a couple courses of 8" tall block to get the wood up above grade so it doesn't draw moisture and rot.
Mike Hawkins

"we usually go a couple courses of 8" tall block to get the wood up above grade so it doesn't draw moisture and rot."

For sure I would lay 3 courses of block, this would also give a ten foot ceiling and still use full sheets of plywood.

 

[firehawkmph]

This topic went way out of line. Constructing a detached building on a ground level slab has been practiced here for decades, it's not going to fall down in any short order or even cause problems if precautionary measures are taken and by the time it does the stability of the house will be much more questionable and of a concern at that time. This is what I have to work with, I'm not ripping out a $10,000 slab. I have my opinions too - why pour concrete only to fasten down cheap wood? The walls should be formed out of concrete and them diamond coated. Let's finish it off with some gold paint while we're at and maybe the queen will visit.

So back to my original questions, any other takers?

Hey Nc,
chill out. I was just telling you how we do things here. Our local codes wouldn't allow what you are doing, just saying. Do what you want, I really don't care, just trying to offer different ideas. You asked for some ideas, that's what you got. Nobody is forcing you to do anything.
Mike Hawkins

 

[GBrackins]

This topic went way out of line. Constructing a detached building on a ground level slab has been practiced here for decades, it's not going to fall down in any short order or even cause problems if precautionary measures are taken and by the time it does the stability of the house will be much more questionable and of a concern at that time. This is what I have to work with, I'm not ripping out a $10,000 slab. I have my opinions too - why pour concrete only to fasten down cheap wood? The walls should be formed out of concrete and them diamond coated. Let's finish it off with some gold paint while we're at and maybe the queen will visit.

So back to my original questions, any other takers?

nc0c7,

sometimes we forget that there are different building codes not only locally, but internationally as well. sometimes we forget that a detached garage such as yours with 440 square feet of area (less than 600 s.f.), and eave height of not more than 10' (9' wall height, no curb) is not required under the 2009 International Residential Code to have frost protection (no need for deep footings or concrete walls). See Section R403.1.4.1 Exception 1.

I understand frustration when postings go in multiple directions and sometimes never provide you with the answers you're looking for.

Posters try to provide helpful information and may make suggestions or comments that are not always requested by the OP. Sometimes they don't want others to have issues they faced and make suggestions.

Sometimes we have to take all comments to get to the ones we want. Not all suggestions are correct, so you have to pick through to find what you need (not necessarily what you want).

I've even been known for posting suggestions that were not asked for, because sometimes we don't think of everything.

what kwik described is how I would construct the walls. front & rear walls are built with parallel plates (top & bottom). When you go to layout your side walls you'll know the wall height at the back and front so you'll have the slope of the bottom plate, if you build with the studs perpendicular to the top plate.

Good luck! :thumbsup:

 

[AllanJ]

I don't think it matters which wall you build first.

Since you already know that the floor slopes, you take that into account when building the walls one at a time.

To guard against propagating miscalculations it would be better to design all four walls (making sure that the end of the fourth wall matches the start of the first wall) before building any of them.

You do have a conundrum when you build framing directly on a slab. It is better for the siding to hang down outside the slab to let rain water drip off, rather than have the slab extend out from the bottom of the wall and collect water. But at the same time the siding must not touch the ground.

 

[n0c7]

No hard feelings to anyone - I do appreciate your time and knowledge, the topic was just going downhill and away from the original question. I'm not committed to anything in particular yet and am evaluating all of my options - including a new topic I created asking about adding a curb onto the existing slab.

 

[n0c7]

You do have a conundrum when you build framing directly on a slab. It is better for the siding to hang down outside the slab to let rain water drip off, rather than have the slab extend out from the bottom of the wall and collect water. But at the same time the siding must not touch the ground.

The last one I did a few years ago the sheathing was flush with the slab. I then installed the siding about an inch below the sill plate - still high enough up that it doesn't touch the ground and also keeps water/snow from melting in. Been 8 years and no water inside.