Two story house with concrete 2nd story floor?

[beppington]

When I was 14-15 I helped my parents physically build our house (2-story). Then, when I was 22-23 they helped me build mine (1-story).

So, I do have experience building a 2-story house, but with wood joists (2x12's).

I'm thinking about building my next house, a 2-story, with a concrete 2nd story floor.

The reason: The house is going in a somewhat low area "near", but not in, areas that can flood. My better half is very concerned about this, so our plan is to build a 2-story house where the ground floor is entirely garage/ utility/ work-shop, & the actual living area is all on the 2nd floor.

I've never liked the feel or sound-travel of wood-joists floors, so, if reasonable, I'd like to be able to make the 2nd floor "seem" like it's a standard, ground-floor concrete slab.

I always appreciate hotels that have concrete floors on the floors above ground floor. They just seem more substantial & quality, & you never hear noise penetrating thru them. I'm not sure how they make them, though. Is it all concrete? Are there steel beams? Are the beams inside the concrete? Is there not actually any concrete at all??

With the work-shop & garage being on the ground floor directly below the living area, & me being a night owl, I'd like to not have to be super-quiet while others are sleeping above.

So, the question: Will it be prohibitively difficult and/or expensive to make the 2nd story floor concrete, compared to wood joists? What might the cost difference be?

 

[/pine]

there is basically two ways...prestressed, precast panels are one way...the other way is using steel bar joists then corregated sheetmetal is laid over the joists and then a slab is poured on the metal...usually lightweight concrete is used...

the precast panels are hollow so plumbing and electric can be run through them

not sure of the cost differential between conventional wood floor systems but I would guess about double the cost of wood...just a guess

 

[rjkobbeman]

There are also floor trusses out there that are extremely stiff/strong.

I used engineered floor trusses made entirely out of 2x4s. They are 24" tall. On 16" centers with 3/4" Advantech subfloor, they are very stiff with no noticeable flex/give. I have some pretty long spans too.

Here is a link to some photos of my floor being put in: Rob & Kirsten's New Home - robert-kirsten-kids' Photos

The concrete idea sounds interesting, but there are other options out there.

If you do go the concrete route, I would LOVE to see pics of that going in. Sounds really neat!:thumbsup:

 

[beppington]

I used engineered floor trusses made entirely out of 2x4s. They are 24" tall. On 16" centers with 3/4" Advantech subfloor, they are very stiff with no noticeable flex/give. I have some pretty long spans too.

What's the sound transfer between floors like with those?

I know with my parents' 2x12 joist floors, 16" o.c., with 3/4" plywood floor surfacing (glued & nailed), R30 insulation, & 1/2" plastered drywall on the ceiling side (below), you can still hear somebody talking thru it, if they talk a little loud. And, if you're on the 2nd floor & jump up & land, a huge boom will reverberate thru the house. In the hotel floors I mentioned, you can jump up & land & it's basically just like a concrete slab on ground.

 

[/pine]

regular glass insulation (R30 insulation) does almost nothing for sound penetration...

they do make sound absorbing insulation for floors etc...

FWIW... the R value of dead air space in horizontal applications (where there is no convection) is quite high...

 

[rjkobbeman]

You can hear everything through my floors. Mine are not insulated, but you're right... that only helps a little.

I hear a lot more in my basement from the upstairs... because of the walking on the floors.

I can hear noise from my basement when I am upstairs, but not as much. I don't know if I will ever insulate my floor... so I can't help you there.

When my grandfather built his home, his basement included the space under his concrete garage floor. You never see that today. I think he did it old-school... a bunch of support underneath with a concrete-and-rebar pour. It was a two stall garage and I can't remember if he had a post in the middle or not for support underneath.

The precast products that /pine mentioned are pretty amazing today. I looked into some precast products to solve a bridge/creek problem I have. Never got beyond the "research" stage though!

 

[dpgood1]

Check your local zoning laws. Most areas require fire resistant material between garages and living areas. CO2 sensors are also a must have, even if local codes don't require them.

One thing that you could look into is sound deadening material. That stuff is usually not cheap.

Go by one of the commercial buildings being built and talk with the contractor to get some ideas.

 

[tallyho8]

My last house had a concrete floor over one bedroom that was the floor for a 2nd story porch.

Every winter we had a bad mildew problem on the bedroom ceiling as water condensed on the cold concrete above.

Your heated area will be above the concrete so your situation may be different.

The floor was very good soundproofing though.

 

[rjkobbeman]

Check your local zoning laws. Most areas require fire resistant material between garages and living areas. CO2 sensors are also a must have, even if local codes don't require them.

One thing that you could look into is sound deadening material. That stuff is usually not cheap.

Go by one of the commercial buildings being built and talk with the contractor to get some ideas.

I have living space above my garages. In my area, "firecode" drywall is all that was required. Had to have "firecode" man doors also.

 

[czechsonofagun]

That type of building is very very common in Europe. Even my dad's cabin has a concrete floor between the basement and first floor. Typicaly I beams (or S beams) and forms and rebar and pour it like a slab.

Or you can use steel beams and build the floor from prefab beams - either concrete or brick clay - it helps with sound proofing and insulation since the brick clay beams are hollow.

All that said - good luck finding it in good ole USA. If it's not a pine dimensional lumber it is very hard to find. One of the ICF makers makes styrofoam beams you put in place and pour slab on top of it. Here, check it out.