Message Board Thread - "Slab on grade foundations"

Back to Threads | Back to Forums

TitleByPosted On
Slab on grade foundations bwrooster 10/1/2009
I work for a builder in the Pacific NW (Portland OR.) They are considering doing slab on grade foundations for production residential construction. They do this in the California division, and believe it can be done here. Being a "native" to the area, I am opposed to this idea. However, just because we do not do it here as a practice doesnt mean I am right. What is the general feeling, pros and cons to this idea? What is the best approach to defend my postion if I am right? Thanks, everyone.
 
Re:Slab on grade foundations Brad Carr 10/1/2009
Just curious why you are opposed to them. They are becoming quite popular in central BC. The only negatives I can see are stairs and possible higher heating and cooling loads.
If your adding an inlaw suite on the lower floor,access is better for the physically challenged and seniors.
Regards, Brad
 
Re:Slab on grade foundations bwrooster 10/1/2009
Brad Carr wrote:
urious why you are opposed to them. They are becoming quite popular in central BC. The only negatives I can see are stairs and possible higher heating and cooling loads.
If your adding an inlaw suite on the lower floor,access is better for the physically challenged and seniors.
Regards, Brad
My main concerns are moisture and drainge issues. Also, I have concerns regarding warranty service calls and accesibilty...lets say, if there was a warranty call for a plumbing drain. Having to jack hammer the floor out of a occupied home ETC... I also question its fesiblity for a production home building schedule due to the amount of rain we get. I have just seen very few builders use that method in this area, with the exception of commerical buildings.
 
Re:Slab on grade foundations Scott Wood Associates 10/9/2009
You have concerns that are typically addressed in the design and construction of the slab. Once the geotechnical engineering has been performed (soils support and drainage, etc.) the area is treated as necessary and proper drainage constructed. Large to medium aggregate is added for a capillary break with a vapor barrier just below the concrete. If preformed as specified drainage and moisture issues are not a problem. Rain and slab pour should not be an issue and is much easer to control moisture once completed then an exposed OSB or plywood floor.
Since we are on an IR post, let us not forget the high heat loss with a vented crawlspace, more typical in our climate here in the Pacifica Northwest. With slab on grade, heat loss due to convention (stack affect) is minimized tremendously and where insulation is required, much easer to apply more effectively below the slab then hanging fluffy stuff under the floor.
I will give you the plumbing below grade concerns, but usually only during a remodel, but can be retrofitted into the walls and ceilings as necessary. Maintenance and warranty should not be necessary unless you use a bad sub.
In most areas of California, slab on grade is done, due to the fast paced construction requirements (quicker, faster, cheaper). In my opinion you see little slab on grade in this area due more to the local construction practices, not due to construction requirements.
 
Re:Slab on grade foundations bwrooster 10/14/2009
Scott Wood Associates wrote:
e concerns that are typically addressed in the design and construction of the slab. Once the geotechnical engineering has been performed (soils support and drainage, etc.) the area is treated as necessary and proper drainage constructed. Large to medium aggregate is added for a capillary break with a vapor barrier just below the concrete. If preformed as specified drainage and moisture issues are not a problem. Rain and slab pour should not be an issue and is much easer to control moisture once completed then an exposed OSB or plywood floor.
Since we are on an IR post, let us not forget the high heat loss with a vented crawlspace, more typical in our climate here in the Pacifica Northwest. With slab on grade, heat loss due to convention (stack affect) is minimized tremendously and where insulation is required, much easer to apply more effectively below the slab then hanging fluffy stuff under the floor.
I will give you the plumbing below grade concerns, but usually only during a remodel, but can be retrofitted into the walls and ceilings as necessary. Maintenance and warranty should not be necessary unless you use a bad sub.
In most areas of California, slab on grade is done, due to the fast paced construction requirements (quicker, faster, cheaper). In my opinion you see little slab on grade in this area due more to the local construction practices, not due to construction requirements.
Thank you for the response Scott, that makes me feel a little better. I truly value your opinion. ;)

I question from a "production" standpoint...if it will be (quicker,faster,cheaper)in this climate. Its gets very damp and cold for long periods of time. Getting the right mix to cure fast enough but not too fast seems like it could be challenging. The acclimation time for certain products such as wood floors could also be challenging. From a warranty standpoint i would LOVE to get rid of crawlspaces dont get me wrong. I just want to be sure if i head down this road i am not shooting myself in the foot.
Thanks again for any input.
 


  • Back to Threads
  • Back to Forums

     

  •   Copyright © FLIR Systems, Inc 2012