Detached Garage

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GatorMD
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Detached Garage

Post by GatorMD » Sat May 19, 2018 3:29 pm

I'm working with a builder and architect to design an unheated 24'x24' detached garage with loft in NY. The builder gave me the option to do a monolithic slab to cut costs vs footings with a foundation. The architect agrees that both options will satisfy local code but the monolithic slab may result in more settling issues. The builder seems to think that the slab will be fine and not cause any issues. The difference in costs will be around $2500 and the total garage costs will be around $36000. Does anyone have any experience with this in my climate (NY). I know there are tons of engineers on this site and I received so many insightful replies when I posted a question about geothermal back when my home was being constructed. Thanks in advance.

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TxAg
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Re: Detached Garage

Post by TxAg » Sat May 19, 2018 3:35 pm

how upset would you be if you get a crack in our garage floor?

Personally, I'd pocket the cash

dickyboy
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Re: Detached Garage

Post by dickyboy » Sat May 19, 2018 3:50 pm

The slab idea should be fine since it is not going to be an attached building. I would pour about 5 inches thick and a little thicker (7" to 8") for about a foot in all the way around the outside perimeter. Also I'd rod the outside perimeter and rods or wire mesh for the interior of the slab. If it floats a bit in the spring when frost comes out of the ground it shouldn't hurt anything. Also treated lumber for the plates around the outside walls is a must.

GatorMD
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Re: Detached Garage

Post by GatorMD » Sat May 19, 2018 3:53 pm

TxAg wrote:
Sat May 19, 2018 3:35 pm
how upset would you be if you get a crack in our garage floor?

Personally, I'd pocket the cash
I agree a couple of cracks here and there in the slab wouldn’t be such a big deal. I was thinking however if I decided to sheetrock the walls in the future will the settlement of the slab cause cracks in the sheetrock that will have to be patched frequently.

bubbadog
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Re: Detached Garage

Post by bubbadog » Sat May 19, 2018 6:33 pm

I am of a differing opinion. I would probably want a below grade footer, especially in a cold climate like NY. How much do you anticipate spending in total on this building?

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Sandtrap
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Re: Detached Garage

Post by Sandtrap » Sat May 19, 2018 6:41 pm

GatorMD wrote:
Sat May 19, 2018 3:29 pm
I'm working with a builder and architect to design an unheated 24'x24' detached garage with loft in NY. The builder gave me the option to do a monolithic slab to cut costs vs footings with a foundation. The architect agrees that both options will satisfy local code but the monolithic slab may result in more settling issues. The builder seems to think that the slab will be fine and not cause any issues. The difference in costs will be around $2500 and the total garage costs will be around $36000. Does anyone have any experience with this in my climate (NY). I know there are tons of engineers on this site and I received so many insightful replies when I posted a question about geothermal back when my home was being constructed. Thanks in advance.
Depends on the soil.
Depends on the expansiveness. IE: clay can heave a building.
Excavate to undisturbed. Fill with mag spec AB compacted.
Footings/foundation/slab can also be done with a monopour and raised sill, steel, concrete wire, fibercrete admix, expansion joints.
Or, depending on soil, monopour with raised sill, grade beams below per area code, steel, etc, etc, etc. Grade beams would be perimeter, two #4 bars horizontal with "L" bars tie in to bars on the slab 24-48" o/c depending on code. Concrete wire mesh., etc.
Either way, below frost line.
aloha
j
Last edited by Sandtrap on Sat May 19, 2018 6:48 pm, edited 1 time in total.

likegarden
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Re: Detached Garage

Post by likegarden » Sat May 19, 2018 6:46 pm

You should not miss to require that the floor is always pitched to the garage door. Their design and settling should not lead to a crack in the middle with part of the floor draining away from the garage door. I also live in NY state and there is always snow melting under the car in winter.
(My comment is because we have an attached garage and had settling issues. It looks like at the side of the house it settled, and that led to a crack in the middle of the floor. Part of the floor is now draining to the house (I framed that part and mop up water), part to the garage door.)

IowaFarmBoy
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Re: Detached Garage

Post by IowaFarmBoy » Sat May 19, 2018 7:18 pm

Sandtrap wrote:
Sat May 19, 2018 6:41 pm
Either way, below frost line.
+1
The monolithic slab is a good option but you do want it to go below the frost line. I used to build houses in Texas and pretty much everything was monolithic slab and they generally worked well. But you do need beams that are big enough and have enough rebar for reinforcement. 30 years ago, our local code required the field of the slab to be 4" and required beams that were at least 18" deep (also had to go 6" into undisturbed soil) around the perimeter and at intervals (like every 12-15' or so- I don't remember) throughout the rest of the slab. We really didn't have frost issues to deal with there. I would want the bottom of my beams (or footers for a conventional foundation) to be below the frost line.

I would assume that local building codes and your architect would address these concerns.

kenoryan
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Re: Detached Garage

Post by kenoryan » Sun May 20, 2018 12:12 am

24 by 24 is too small. Go bigger.

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lthenderson
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Re: Detached Garage

Post by lthenderson » Sun May 20, 2018 8:21 am

GatorMD wrote:
Sat May 19, 2018 3:53 pm
I agree a couple of cracks here and there in the slab wouldn’t be such a big deal. I was thinking however if I decided to sheetrock the walls in the future will the settlement of the slab cause cracks in the sheetrock that will have to be patched frequently.
I've done both methods many times and if properly poured for the soil conditions below frost line, neither one is more likely to crack than the other one. However, concrete in large expanses, poured monolithic or as a slab especially 24 by 24 feet, WILL crack as it cures over time. My solution has always been to score the concrete with a concrete saw in no more than 10 feet by 10 feet squares. For a 24 by 24, I would go 8 by 8 feet squares to make it come out even. You cut down with a concrete saw more than half the thickness of the concrete but above the level of the reinforcement rod. What this does is give the concrete an easy place to crack but since it happens in the joints you cut, it really is never visible and looks much better than a crack that randomly zig zags across the floor. The cracks you cut fill up with packed dirt and really look like a grout line over time and the reinforcement rod prevents it from shifting vertically. The reason you don't cut down to the level of the reinforcement rod (which properly installed should be in the bottom third of the concrete slab) is so that air and moisture is not introduced to the encapsulated metal to rust it out prematurely. I have helped pour slabs nearly 40 years old at this point that have no visible cracks other than the joints I cut in them 40 years ago.

GatorMD
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Re: Detached Garage

Post by GatorMD » Sun May 20, 2018 2:22 pm

Thanks for all the informative responses. It seems like the general consensus is that whichever option I go with to be sure that it’s dug below the frost line. Thanks again.

CurlyDave
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Re: Detached Garage

Post by CurlyDave » Sun May 20, 2018 10:34 pm

kenoryan wrote:
Sun May 20, 2018 12:12 am
24 by 24 is too small. Go bigger.
I agree. My 30' x 30' garage is too small.

* * * on edit * * *

If you are going to park 2 cars in it, splurge on an 18' wide door instead of the usual 16' wide. I did this and am very happy with the extra width it gives to get in and out.

IowaFarmBoy
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Re: Detached Garage

Post by IowaFarmBoy » Mon May 21, 2018 6:17 am

GatorMD wrote:
Sun May 20, 2018 2:22 pm
Thanks for all the informative responses. It seems like the general consensus is that whichever option I go with to be sure that it’s dug below the frost line. Thanks again.
The other basic thing is to follow the local codes and recommendations from your architect. They will be adapted to your conditions. For example, the advice I gave was based on my experience building in Texas with highly expansive clay soils and no real frost risk and I tried to extrapolate to your conditions.

Good luck!

Jack FFR1846
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Re: Detached Garage

Post by Jack FFR1846 » Mon May 21, 2018 7:18 am

Ask a local civil engineer. Our 24x36 garage in eastern Ma has footings as required by local code.
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Glockenspiel
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Re: Detached Garage

Post by Glockenspiel » Mon May 21, 2018 8:58 am

I'd build to whatever the local building code requires and nothing more. In NY, I'm guessing the state building code will have requirements for footing depths. This could be 24"-60" deep, depending on local frost depths.

I'll echo others and say build it bigger if you want to fit 2 cars in it. Yes, you need to cut joints into it, otherwise you will have cracking in very short order. And yes, ideally the concrete surface should slope 2% (1/4" drop per foot of length) towards the garage doors.

ddurrett896
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Re: Detached Garage

Post by ddurrett896 » Mon May 21, 2018 10:01 am

CurlyDave wrote:
Sun May 20, 2018 10:34 pm
kenoryan wrote:
Sun May 20, 2018 12:12 am
24 by 24 is too small. Go bigger.
I agree. My 30' x 30' garage is too small.
There is no such thing as a garage too big. Unfortunately, we are confined to codes and setbacks!!!

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Sandtrap
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Re: Detached Garage

Post by Sandtrap » Mon May 21, 2018 10:15 am

IowaFarmBoy wrote:
Mon May 21, 2018 6:17 am
GatorMD wrote:
Sun May 20, 2018 2:22 pm
Thanks for all the informative responses. It seems like the general consensus is that whichever option I go with to be sure that it’s dug below the frost line. Thanks again.
The other basic thing is to follow the local codes and recommendations from your architect. They will be adapted to your conditions. For example, the advice I gave was based on my experience building in Texas with highly expansive clay soils and no real frost risk and I tried to extrapolate to your conditions.

Good luck!
Also in Northern Arizona.
Beware those expansive soils (clay) = $$$$$$
j

forgeblast
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Re: Detached Garage

Post by forgeblast » Mon May 21, 2018 10:51 am

Make sure they use chairs on the rebar. Do not trust them to pull the mesh up while pouring it will end up on the bottom. Rebar it and you will not have the issues of mesh.

GatorMD
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Re: Detached Garage

Post by GatorMD » Mon May 21, 2018 11:23 am

I was initially going to go with a 20'x20' which would probably have been too small. I think 24'x24' should be fine since I only plan on putting one car in there and a sidexside in the other bay. The garage will have an upper level for a work bench and storage. I already have an attached 2 car garage for the family car and my commuter. Thanks again for everyone's input so far.

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