concrete garage floor: bolts or not?


  #1  
Old 02-19-04, 09:31 PM
gab2nanstan
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Question concrete garage floor: bolts or not?

HI: I am planning to replace my garage floor and have had 2 contractors tell me different ways to do it. The first says to put bolts into foundation walls to join the floor and walls then use crushed stone and 5" of concrete; essentially creating one structure. The second contractor suggests not using bolts at all but leaving the floor seperate with crushed stone and 4" of concrete. Any suggestions on which approach is correct/best?
Thanks for any info.
 
  #2  
Old 02-19-04, 11:14 PM
millertime
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Re: concrete garage floor: bolts or not?

Originally posted by gab2nanstan
HI: I am planning to replace my garage floor and have had 2 contractors tell me different ways to do it. The first says to put bolts into foundation walls to join the floor and walls then use crushed stone and 5" of concrete; essentially creating one structure. The second contractor suggests not using bolts at all but leaving the floor seperate with crushed stone and 4" of concrete. Any suggestions on which approach is correct/best?
Thanks for any info.

both methods are correct, but the 5" of concrete, and the bolts would be the "best" out of those 2. There are also many other methods that can be used.

could you tell us the dimensions of the garage, why you plan to replace the floor, how old it is. and the prices they gave?
 
  #3  
Old 02-20-04, 03:12 AM
B
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Where is ground level outside the garage wall with respect to the garage floor level? Is there a space between the old floor and the foundation wall?

I have to replace my garage floor soon and need to correct a problem that you may also have. The original builders in the 50's used an 8" block for the foundation wall and then set grade outside at about 3-1/2' below the garage floor. Of course, the foundation wall has now tipped out; there is about 1-1/2" between the slab edge and the block. Every 3'-4" I am planning on putting a reinforcing rod down the block wall (and grouting the block cells) and then bending the rod horizontal near the top so it is poured into the new floor slab. This will reinforce the wall and tie the wall to the floor slab so it won't tip any further than it already has.

You don't say where you live, but if you live in a northern climate subject to freeze/thaw and salt deicers on the roads, I would recommend using a 4,000psi concrete mix with an air entraining admixture. That will give the concrete a lot more resistance to salt and freeze/thaw.

Bruce
 
  #4  
Old 02-20-04, 09:13 PM
gab2nanstan
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Re: Re: concrete garage floor: bolts or not?

Originally posted by millertime



both methods are correct, but the 5" of concrete, and the bolts would be the "best" out of those 2. There are also many other methods that can be used.

could you tell us the dimensions of the garage, why you plan to replace the floor, how old it is. and the prices they gave?
thanks 4 the info. in response 2 your questions, the garage measures 23'w x 22'd, built in the 50's (michigan) and is being replaced because it is cracked and the front left side has sunk where there is a brick wall (decorative). price for the 5" with bolts was $7245.00 including the driveway as well. 4 the garage only was $4345.00. the contractor that said no bolts with 4" quoted $6700.00 for both the driveway and garage (prices not listed seperately). thanks again!
 
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Old 02-20-04, 11:44 PM
ilketile
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not sure where you live but i believe id ask around for a few more quotes those both sound kinda high to me that is not nowing how big driveway is
 
  #6  
Old 02-22-04, 04:29 AM
h.h.
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Yeah, sounds like about 7 yd.s(23'x22') of concrete.At $60.00 a yard for a 6 sack mix coming to $480.00.A 6'retainer wall costs about $25 a running foot for materials.(23+22+23)x25 comes to $1700.00,a total of$1,180 for materials.A pretty good profit.
 
  #7  
Old 02-22-04, 10:16 PM
millertime
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Re: Re: Re: concrete garage floor: bolts or not?

Originally posted by gab2nanstan


thanks 4 the info. in response 2 your questions, the garage measures 23'w x 22'd, built in the 50's (michigan) and is being replaced because it is cracked and the front left side has sunk where there is a brick wall (decorative). price for the 5" with bolts was $7245.00 including the driveway as well. 4 the garage only was $4345.00. the contractor that said no bolts with 4" quoted $6700.00 for both the driveway and garage (prices not listed seperately). thanks again!

that is a lot of money. can you measure the dimensions of the driveway for us. and what kind of a finish the driveway will be.

also, if you plan on spending that much, you should definitely consider installing rebar. (the rebar can also be installed into the foundation by drilling a hole, and epoxying it in). ask your contractor what the cost of rebar would be, because it would be a shame to spend all that money, and have it crack and settle in a couple years.
 
  #8  
Old 02-23-04, 04:20 AM
B
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If the existing slab is settling, it's because the ground below the slab was not properly compacted when it was backfilled; see that a lot in residential construction (and occaisionally in commercial construction). The proper way to correct the problem is to dig out the problem area and put it back, machine compacting it in 6" to 12" lifts. If this is done and the compaction is adequate, the slab doesn't need to be tied into the wall and won't settle. A 4" thick slab is fine for this.

If you don't dig out the bad fill, then you have to design the floor as a structural slab to span over the bad fill and tie it into the wall. If the wall being tied into is brick, you can epoxy the rods in; if it's hollow block, then you have to grout the cores where the rod is set in. Tie the slab into the wall with #4 dowels @ 12" to 16" o.c. Then reinforce the slab with #4 bars @ 12" o.c. each way. Be sure the reinforcing is in the bottom 1/3 of the slab or they will do no good. At a minimum, I would do this where you have the settlement problem, but you may want to do the entire perimeter on the theory that if it's bad in one area there is potential to have other bad areas that have not shown up. I would suggest a 5" slab where the bad area/reinforcing is, 4" elsewhere.

Since you are in an area of the country subject to freeze/thaw and road salt, I would strongly recommend 4,000 psi, 6 sack minimum concrete and an air entraining admixture.

Hope this helps.

Bruce
 
 

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