At the moment, I am trying to figure out the process of getting engineering drawings for a foundation. – seemed like a simple task.
The one story house is a 100 foot long rectangle on one level with the garage on one end, the house on the other, and a breezeway seperating the two. Due to the slope of the land, the garage foundation will be a slab on fill, almost certainly supported by piers. Nobody does fill compaction for residential construction in this area – or so I have been told. The rest of the house will be on pier and beam with a big crawl space. That means that somewhere there is going to be some sort of transititon between the slab on piers part and the pier and beam part.
So, I figured I would hire a foundation engineering firm to design the whole foundation, tell me how much fill and where, what the transition would look like, and off we would go.
However, the foundation engineering companies are all telling me to come back after I have the fill in place and that seems backwards to me.
In my mind, that means that I take the results from a soil test, make my best guess as to what the engineering company is going to end up with, hire the fill work done (about 120 yards), and then hire the foundation engineering firm to take my guess work design and fill in the details.
I’m capable of coming up with something that will work, but it sure seems like the hard way to get there.
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I'm capable of coming up with something that will work, but it sure seems like the hard way to get there.
I agree. Our engineers will create a plan from the soil test prior to any fill, and they specify the fill composition and compaction.
As a backwoods engineer, I would definately be concerned about the two foundation types and their connective relationship.
I would express the things you stated in your post to the engineer(s).
I've tried talking to some of the foundation engineering firms in this area and I brought up my reservations about the transition and putting the fill in before I contracted with them - which brought me to post this topic.
I've got a couple more firms to talk to and I'm still hoping to find an answer that makes more sense to me.
Until I get the soil test done, I don't know the soil type for certain. However, it appears that I don't have the expansive clay soil that covers a lot of the Fort Worth area. This soil has a lot more sand and rock to it, and where I'm building, there is very little top soil at all.
The vast majority of homes built in this area are slab on grade. The normal sequence appears to be after the fill is brought in any compaction is done with a full dump truck driving back and forth over it. If they do a soil test at all, they run the soil test drill through the fill and send that information to the foundation engineer, assuming they even use a foundation engineer.
With at least three or four feet of fill dirt under one end of the garage slab, compacted or not, I am not willing to trust anything less than piers supporting the slab. Since the rest of the house will be on piers, I have to believe that piers under the slab is the only answer.
I'm still thinking about the best way to transition between the two parts. I'm really bright, but I'm an electrical engineer, not a foundation engineer.
paul.. if there is no question of expansive clay, then why not pour a standard stem wall foundation
the footing will go on bearing soil ( undisturbed subsoil ) .. the footing will be stepped as the grade changes, your footing might be 4' below grade at the low side and one foot at the high side ( i don't know what your design frost depth is )
then you pour your standard wall on top with the top of foundation all at one level
your excavation sub then ramps up and dumps the suitable material inside the foundation .. a backhoe with a grading blade spreads it ... and you compact it in place with a plate compactor and some moisture
until you have the compaction you want for your slab-on-grade
seems like a lot less work than pouring piers and dodging them
Mike Smith Rhode Island : Design / Build / Repair / Restore
The slope of my lot would mean more than 800 yards of fill and 9 foot high stem walls at one end.Besides I really like the idea of the big crawl space. The air handler, water heater, duct work, all go in there with lots of storage space left over.
in a just world... you got a discount on the lot that will pay for the additonal foundation costsMike Smith Rhode Island : Design / Build / Repair / Restore
Yes, we did get a discount on the lot. We also got some beautiful huge live oak trees, a lot more privacy than you normally get inside city limits, and when we are done, it is not going to be just another cookie cutter McMansion.The lot is part of what used to be a horse ranch and there are still horses on either side of our property. There are no home owner orginizations and this all fits in perfectly with our lifestyle.I just have to keep plugging away at all the details and get it built on budget.
here how it works, I am a geo tech. I need to know what type soil is under a bldg, it could be swamp mud, rock, beach sand, then I need to know about water table and anything extra like hill, slope, highway vibration, underground stream, cave, mines, etc.I calulate what that one site will hold pounds per square foot, then I send that info to the stuctual engineer who takes the weight of the building and calculates the foundation..
Edited 2/2/2007 11:14 pm by brownbagg
I am outside of Houston. Most foundations here are (also) slab on grade. Many areas have highly expansive clay.
Our fill procedures are similar. Compaction works best if it is done in 8" lifts (8" of spread fill, roll and bring in the next loads). Our 7000 lb skid loader, used correctly will compact select foundation fill to the required 95% Standard Proctor Compaction Test.
I'm still thinking about the best way to transition between the two parts. I'm really bright, but I'm an electrical engineer, not a foundation engineer.
I still think the transtion and connective relationship is worth some attention.
I built a home years ago down in Palacios on the coast. It was designed to have a slab on grade, but had a wrap around porch that the designer had shown on piers.
I was concerned as in your case. We performed our foundation engineering, and our engineer confirmed my concern. He specified continuation of the slab on grade through the Porch, or a drilled and reamed 12/36 pier and beam for both home and porch.
The HO had lived in a pier and beam in her youth and wanted a slab on grade. Perhaps she was critter concerned.
In the designers sugggested plan, the engineer was concerned about the frame connection of the porch to the house and that the home and porch structures were on two types of foundations with differing movement.
There is more to the story, as we made the slab on grade appear to be pier and beam as originally intended by the designer, but you catch my drift.
Until I get the soil test done, I don't know the soil type for certain.
That's the first step. Either you can do it before going to the engineer, or the engineer can have it done, but they need that info.
Beer was created so carpenters wouldn't rule the world.
paul... where are you ?
is this some of that expansive clay soil... or just regular sub-soil ?