FL Residential Post Tensioned SOG - Field Review

[KootK]

I'm looking at doing a residential PT SOG in a far away jurisdiction. And I'm trying to get a feel for a) whether or not I want to do that and b) how I should price it. My specific questions are:

1) Given that PT SOG is a popular thing in some markets, is it safe to assume that it's generally cheaper to construct than pile and grade beams? In my home market, that would not be the case.

2) How much field review do we think needs to be done for something like this? I'm thinking shop drawing review, a single in person field review pre-pour, and review of elongation results.

3) What can I expect the construction team to look like for something like this? Contractor experienced at this kind of thing or green rookies fumbling around in the dark?

4) Any sense for what design only fees for these things typically are? I'm planning to pitch about $4K.

 

[JoelTXCive]

I was a homebuilder in my pre-engineering life.

I'm not sure about your final decision on picking up this work, BUT I have one item to inquire about prior to doing a design if it applies.......

Is the builder/customer/homeowner going to be purchasing a 3rd party warranty on the home? In Texas these are generally referred to as '2-10 warranties' (2 years mechanical & 10 years frame + foundation)

The large national warranty companies often have their own design guidelines that must be complied with prior to writing a policy. For post tensioned slabs, they often require that the engineer sign off that the slab complies with PTI design standards. The warranty company can also dictate max beam spacing and pad sizes for a geographic region. Usually there is nothing crazy in their guidelines, but it is something you probably want to be aware of on the front end.

 

[hokie66]

Why would you use "PT SOG" in Florida? Is there a specific problem that this is supposed to address?

 

[KootK]

@JoelTXCive: it was your very voice that I was hearing in my head when I posted my question as I know that you have some direct experience with this. Thanks for chiming in. Any chance you'd be able to share your experiences with regard to items #1 through #4. I'll definitely look into the insurance piece a you kindly recommended.

Why would you use "PT SOG" in Florida? Is there a specific problem that this is supposed to address?

It's used in some markets to deal with expansive clay situations as an alternate to deep foundations. Apparently, the project location has expansive clays. I actually have the geotechnical reports for the properties either side of mine. One went with piles and grade beams, the other post pensioned SOG.

 

[Huevo]

1) Given that PT SOG is a popular thing in some markets, is it safe to assume that it's generally cheaper to construct than pile and grade beams? In my home market, that would not be the case.

In Texas, Yes.

2) How much field review do we think needs to be done for something like this? I'm thinking shop drawing review, a single in person field review pre-pour, and review of elongation results.

In general, that's what happens. Sometimes more depending on specifics.

3) What can I expect the construction team to look like for something like this? Contractor experienced at this kind of thing or green rookies fumbling around in the dark?

Generally tend to be more experienced than not.

4) Any sense for what design only fees for these things typically are? I'm planning to pitch about $4K.

Varies widely but somewhere in the $1/sf neighborhood depending on complexity and size.

 

[a2mfk]

Hokie66- long time no speak. Decided to come back on for some research on another topic and thought I would chime in. There are some regions of very plastic (shrink/swell) clay from north of Tampa (Brooksville) all the way up the I-75 corridor, including Ocala, Gainesville and Lake City. I spent about 8 years with a company that did a lot of soil testing throughout this area and the rest of Florida, and I have seen clay due horrible things to structures, causing 2-3" of differential vertical movement from one side of a house to another. Having been privy to the soil reports, you would not believe the variability of soil depths and properties within a very short distance (average house footprint).

So with all that said - due to the litigious nature of building construction in Florida, I would be very cautious becoming involved with any expansive soil projects. I am mainly on the forensic side of the structural and building engineering, so I see what goes wrong down the road several years or more after construction. It doesn't matter if the drywall and stucco cracks are the result of foundation movements or not, you may get pulled into a lawsuit down the road. I would want a very tight contract limiting your liability, and I would want to see the building drawings. There are still lots of houses signed and sealed by architects (and some engineers) who either don't have a clue , or worse, just plan stamping. Since so many building issues can be blamed on the slab and foundation (whether right or wrong), you could get pulled into something. Who is the overall contractor and their resume? And if this is wood frame with stucco, run away, don't walk. It will crack sooner than later from a lot of different causes. Stucco on wood framing in Florida is a big problem and it is only going to get worse.

Good luck.

 

[hokie66]

Good to hear from you again, a2mfk. Figured you were just too busy to argue with us old timers.

Where I am, in Queensland, Australia, we have similar moisture sensitive clay in places, but we don't use the type post-tensioned slab on ground slabs they like in Texas. I don't know how much success they have, but have my reservations.

 

[Ron]

KootK....where is your property in Florida? As a2mfk notes (by the way a2...welcome back and hope things are going well since your move), there are some "hot spots" for expansive clays at the surface. As he notes, the northern I-75 corridor is one, but it also extends westward along I-10 for about 50 miles into the Madison area, east of Tallahassee. While clays exist east of I-75, they are generally less expansive. As an example, west of the St. Johns River in the Jacksonville area, there are pockets of surface and near surface clays that are generally not expansive but create the other problems that clays present in construction and constructability.

 

[EZBuilding]

If you pitch 4K, I'd recommend having construction administration, including site visits, as hourly. Flight down from our neighbor up North has to eat up at least 2-3 days...

 

[KootK]

KootK....where is your property in Florida?

Gainesville. I've got the soils reports for the two adjacent buildings and it definitely appears that this location is a hot spot. One of the neighbor buildings went piles and grade beams, which is what we do exclusively in Alberta. The other building went PT SOG which I assume is a less robust but more economical solution. I'm hoping to get some info on the neighbor buildings to get a sense for how well they've performed so far.

If you pitch 4K, I'd recommend having construction administration, including site visits, as hourly. Flight down from our neighbor up North has to eat up at least 2-3 days...

I went in with an extra $2,500 for a mandatory pre-pour field visit and hourly for anything else that's required. That's basically cost with me working at a crap rate for a couple of days. As you've anticipated, I'm at a reverse competitive advantage when it comes to actually showing my face. This project comes with additional complexities beyond the expansive clay business that make it a less desirable assignment. It's one of those cases where I don't especially want the project but I very much want the relationship with a new client. They do a decent volume of work and wish to single source structural. As you can imagine, turning down the first job didn't appeal to my atrophied business sense.