Elevated floor on piers vs slab

[FrankInWI]

Would you guys do me a favor and answer a question I'm sure has been asked before? 

Son was near me and we were discussing some posts in this great forum.  This is my elder son who helped me SO much on our get-away.  W
We went with a concrete slab instead of the raised floor on piers.  As we were looking at some pictures he asked me "why did we put in a slab versus building it up on piers like that?"   

What are some of the pros and cons of the two differenet approaches.. Slab floor vs raised on piers?

[rwanders]

Slab Foundation:

Pro:  Less Expensive since you do not need beams, floor joists, sub floors, etc.

Con: Requires more forgiving soils---doesn't do well in frost prone soils
       
       Requires more concrete---may be problem if truck access is difficult

       Plumbing connections are buried and hard to reach if you need to.

       Difficult to insulate floors

       Many DIY's don't have concrete finishing skills needed to do the work

Piers & Elevated Floors:

Pro:  Doesn't have the cons noted above.

Con: doesn't have the pro noted above.

Probably more but I can't think of them right now.

[rdpecken]

Hi Frank.

The biggest advantage for our build was that I could make the piers myself, without the necessity of getting a cement truck from the nearest town (55 miles away) at around $150 per yard.  It also meant that we didn't have to build a "pad" or level the ground at all.

Randy

http://www.arizonaranch.org

[MountainDon]

If you leave the DIYer skills out of the equation, slab has a lot of advantages in many areas. Here in the SW it is the foundation of choice. If you are building in an area where flooding is a possibility the raised floor post and beam foundation offers some obvious advantages. If you have to dig down 4 to 5 feet to get below the frost line for a foundation, a basement begins to be less costly because you may already have the need to dig a deep perimeter footer.

Slabs do require very careful plumbing supply and waste line placement. Burying the lines is not much of a problem if care is taken and something like PEX used for supply lines.

Raised floors can be a PITA for crawling under and insulating. They elevate the house for a better view.

Basements can be a problem in areas with high water tables.

[tc-vt]

Slab pros:

No crawl space for critter and moisture problems, but then, the lack of plumbing access is a con here

Can do radiant heat easily

You can insulate under the slab with polystyrene (Dow blueboard or Owens-Corning pinkboard)

A slab *can* be done in a cold climate as a Frost Protected Shallow Foundation, without having to go below frost line

The slab can be your finished floor with colorings, exposed aggregate finishes, etc (wish I did that)

Tom

[Don_P]

Can you cite for me how to build a prescriptive pier and beam foundation?

Also don't forget a permanent wood crawlspace foundation for enhanced strength.

I'm on a raised slab on the south side with no plumbing in that side but it does have radiant tubing. The north side is over a crawlspace where the plumbing and most wiring runs are. I poured a rat slab under there and its a nice storage area.

[Bill Houghton]

Would you guys do me a favor and answer a question I'm sure has been asked before? 

Son was near me and we were discussing some posts in this great forum.  This is my elder son who helped me SO much on our get-away.  W
We went with a concrete slab instead of the raised floor on piers.  As we were looking at some pictures he asked me "why did we put in a slab versus building it up on piers like that?"   

What are some of the pros and cons of the two differenet approaches.. Slab floor vs raised on piers?

Frank, we have decided to go with a pole type building with a slab floor.  The frost protected shallow foundation method mentioned above will be incorporated into our design.  I see the pros as in floor heat, easy to clean up (sweep), and holds heat if well insulated.  Cons are its hard on your feet and legs with long periods of standing (like in the kitchen). 

Bill in the U.P.

[MountainDon]

I have read that in some locations, like north Texas, slab on grade foundations are a poor choice and pier and beam are preferred.

Can't find the article at present though.

[Don_P]

I believe NOLA is requiring it for floodwaters to pass thru, not positive. I do know they have stopped allowing people to build a mound above flood level to perch atop, this caused floodwaters to inundate their neighbors.

I have posted a question on the ICC forum related to this, I asked about my state, VA, thus far it looks like "design required", I'll post more if it changes. It requires an engineer's review of the foundation to make sure it is up to transmitting the loads safely. This is a good idea especially for owner builders as missing a detail can cause loss of the structure or worse.

[tc-vt]

Here are some links on foundation options:

http://raisedfloorliving.com/index.shtml\

http://www.builderswebsource.com/buildingadream/foundations.htm

http://www.smartvent.com/pdfs/SV_RaisedFdn_DesktopPrint.pdf

http://www.houston-slab-foundations.info/Buyer's%20Guide%20to%20Slab-on-Ground%20Foundations.pdf


Tom