General concrete questions

[Bradbilt]

Well the structure of the building is almost up.

The next step would be utilities and floor.

I am planning on 3 zone radiant heat.

There will be one floor drain in the wash bay. I am thinking one of these 4" x 12' drains right up the middle of the bay.

My question is the floor thickness. Will 5", 4000lb, wire mesh, & Fiberglass be strong enough?

The HEAVIEST thing that I will ever put in the garage is a semi truck that weighs 16-18,000lbs It is 22' long and the weight is spread out on 10 tires.

I also plan on installing a 12-15k 2 post lift. They recommend a 6" floor. Can I get away with 2'x2'x 8" cubes where the lift will be?

I was pricing out 6" and I had to sit down for the $20-22k quote. That blew my socks off for a 4800sq/ft

What about thermal breaks to operate the 3 zones? Would a piece of trex and some sill seal on either side be sufficient? There will be a wall build on each thermal break


Thanks for any and all responces

 

[ConCretin]

Give my Guide to Floor Slabs in the link below a read for some additional thoughts but to answer your question, yes. With a properly constructed base, a 5" slab is more than adequate for all but the heaviest uses.

Reinforcing and fiber mesh don't factor into the 'strength' discussion. Fiber is designed to delay early age shrinkage cracks, which can buy you time to saw cut control. Steel reinforcing, wire mesh or rebar just hold cracks together.

The strength of your floor is entirely a product of your base, the thickness of your slab and to a lesser degree, the compressive strength of your concrete mix. A solid base and 5" of 4000 psi concrete is all you'll ever need.

I would thicken the slab where your lift will go and I wouldn't bother with thermal breaks between heating zones.

 

[SALIV8]

^ I'd listen to him

 

[joes169]

Give my Guide to Floor Slabs in the link below a read for some additional thoughts but to answer your question, yes. With a properly constructed base, a 5" slab is more than adequate for all but the heaviest uses.

Reinforcing and fiber mesh don't factor into the 'strength' discussion. Fiber is designed to delay early age shrinkage cracks, which can buy you time to saw cut control. Steel reinforcing, wire mesh or rebar just hold cracks together.

The strength of your floor is entirely a product of your base, the thickness of your slab and to a lesser degree, the compressive strength of your concrete mix. A solid base and 5" of 4000 psi concrete is all you'll ever need.

I would thicken the slab where your lift will go and I wouldn't bother with thermal breaks between heating zones.

Doug, have you had any exposure or experience with macro fibers yet? We've been trying out "Forta-Ferro" fibers a few times in the last few years here. They're getting spec-ed out to replace steel on a ton of commercial jobs as well. I've actually seen a few examples that are years old now,and they are holding up very well. One of the most impressive was a large warehouse with extended joint spacing at 94' centers, with a column line at 47'. No visible shrinkage cracks anywhere.

I do tend to agree that standard "Fibermesh" get's misused all too often. I've been around this stuff long enough to see a lot of contractors (and homeowners) get burned by emitting steel years ago when the Fibermesh wave came through.........

 

[Bradbilt]

Give my Guide to Floor Slabs in the link below a read for some additional thoughts but to answer your question, yes. With a properly constructed base, a 5" slab is more than adequate for all but the heaviest uses.

Reinforcing and fiber mesh don't factor into the 'strength' discussion. Fiber is designed to delay early age shrinkage cracks, which can buy you time to saw cut control. Steel reinforcing, wire mesh or rebar just hold cracks together.

The strength of your floor is entirely a product of your base, the thickness of your slab and to a lesser degree, the compressive strength of your concrete mix. A solid base and 5" of 4000 psi concrete is all you'll ever need.

I would thicken the slab where your lift will go and I wouldn't bother with thermal breaks between heating zones.

No thermal breaks?!?!

Why not? Will I not "loose" heat without the thermal breaks?
One part of the building will NOT be heated, but I plan on putting pex in it for future

I read your link. VERY informative

 

[ConCretin]

Doug, have you had any exposure or experience with macro fibers yet? We've been trying out "Forta-Ferro" fibers a few times in the last few years here. They're getting spec-ed out to replace steel on a ton of commercial jobs as well. I've actually seen a few examples that are years old now,and they are holding up very well. One of the most impressive was a large warehouse with extended joint spacing at 94' centers, with a column line at 47'. No visible shrinkage cracks anywhere.

We haven't seen the macro fibers much up this way but from what I've read, they seem to be quite effective at limiting shrinkage and curling. Sounds like your observations back this up. Fewer control joints and less curling is a huge deal in big commercial/industrial floors.

I guess I still have trouble seeing them as a substitute for steel reinforcing as they still perform different functions but maybe the macro fibers will fulfill the promise of fiber-mesh.

Might be worth a try if a garage builder really wanted to avoid control joints. If you pay close attention to base, slump, etc. and don't get any cracks, there really isn't any need for reinforcing. Not sure I'm that brave though.

No thermal breaks?!?!

Why not? Will I not "loose" heat without the thermal breaks?
One part of the building will NOT be heated, but I plan on putting pex in it for future

When you said three zones, I assumed you were heating all three. It didn't seem worth the trouble to isolate them from one another as the temperature differential would be modest.

Installing a thermal break mid-slab can be complicated. You need to form the slab into separate placements and install your material between pours, which is expensive -or- somehow hold the material in place and pour on both sides, which can be a little difficult with finishers thrashing around.

If one of the zones is un-heated, it might be worth the extra effort but I'm still not sure I'd bother. Others with more knowledge might disagree.

 

[Bradbilt]

Ok, I appreciate the input. Dropping from 6" to 5" will save me $1400 that I could really use elsewhere.

How far apart should expansion joints be?
Which is better, saw cuts or those zip tips?

BTW the building is 40' deep 120 long

 

[ConCretin]

Ok, I appreciate the input. Dropping from 6" to 5" will save me $1400 that I could really use elsewhere.

How far apart should expansion joints be?
Which is better, saw cuts or those zip tips?

BTW the building is 40' deep 120 long

To be safe i.e. give yourself the best chance to avoid random cracks, you could cut CJ's at 10' centers. If you don't want to look at that many cuts and a random crack won't ruin your day, you could likely get away with half that number.

To maximize spacing, you need to minimize shrinkage. There is a lot to this but larger 1 1/2" aggregate, mid range water reducer, fiber mesh, placing in cool weather, etc. will all help. It's also important to cut the joints in a timely manner.

I prefer saw cuts over zip strip. They do the same thing and zip strip goes in sooner so it's actually better in that regard. I just find it a PITA to put in and get it straight.

 

[matt_i]

I'd put some thought into what insulation you're going to use.

While the 25psf would seem to be enough it also depends on the appropriate thickness of concrete to spread out the load.

I want to say 40psf is available via special order, likely for heated airport runways which have more load and potential impact, etc.

In my build I planned for forklift traffic for rigging machines, I omitted insulation (no hydro heat anyway) and omitted sand in the base because of an article I read about it causing potential issues with heavy point loading and went with just the #57s compacted.

Make sure you have a good plan to keep the slab hydrated (vapor barrier and wet curing or curing sealer) to maximize concrete strength. Don't let your contractor pour a soupy mix. It might be good to consider having it pumped to maintain the original mix.

 

[WIHD]

Give my Guide to Floor Slabs in the link below a read for some additional thoughts but to answer your question, yes. With a properly constructed base, a 5" slab is more than adequate for all but the heaviest uses.

Reinforcing and fiber mesh don't factor into the 'strength' discussion. Fiber is designed to delay early age shrinkage cracks, which can buy you time to saw cut control. Steel reinforcing, wire mesh or rebar just hold cracks together.

The strength of your floor is entirely a product of your base, the thickness of your slab and to a lesser degree, the compressive strength of your concrete mix. A solid base and 5" of 4000 psi concrete is all you'll ever need.

I would thicken the slab where your lift will go and I wouldn't bother with thermal breaks between heating zones.

I see the 5" comment (useful, thx)....though if one did do rebar as well, is #3 suggested? or #4?

 

[bad_idea]

Might I suggest 4" on a portion of the shop and 6" on the other portion? Pour 4" in the areas where you can get away with it - storage areas, woodworking area, etc. Pour 6" where you need the extra thickness - lift bay, bay for tractor trailer, etc. Cost-wise it should balance out.

 

[ConCretin]

I see the 5" comment (useful, thx)....though if one did do rebar as well, is #3 suggested? or #4?

The only reason to go with #4 bar is that's it more rigid than #3 bar or mesh for that matter. They all perform the same function IF they are located properly in the slab. The more flexible the material the more supports are required to keep it up with finishers traipsing all over it.

Although it's a bit arbitrary and probably overkill, I usually say #4's @ 24" supported every 4', #3's at 18" supported every 3' or 2.9 mesh supported every 2 feet.

 

[Armorpoxy]

Hi,
Regarding the fibers they can make coating with an epoxy difficult if you plan on doing that s the fibers need to be either burned off with a landscaping torch, or epoxy primed to stiffen them and then grinded off.

 

[Bradbilt]

Hi,
Regarding the fibers they can make coating with an epoxy difficult if you plan on doing that s the fibers need to be either burned off with a landscaping torch, or epoxy primed to stiffen them and then grinded off.

I'm pretty sure I am going to go with ghost shield or some similar clear sealer