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> Foundation footings set to bedrock and insulated above the freeze line Not knocking it, but is this normal for single family home construction? Is it possibl

> Foundation footings set to bedrock and insulated above the freeze line Not knocking it, but is this normal for single family home construction? Is it possible with reasonable cost? Is it primarily for an earthquake-prone region? The idea is cool, but I thought only skyscrapers went down to bedrock.

tristor 5y ago
The answers to your questions definitely vary by region. If you're building a house, one of the first things you should do is get a structural engineer's assessment of the lot before you plan the foundation, because soil type, bedrock depth, freeze lines, environmental concerns, etc. all affect this. But yes, it's fairly common to do this if you care about structural integrity over the long term. In areas with soil type that support it, it's more common to do simple slab foundations without footings, but in most of the US footings are used and the foundation is built as part of a crawl space or basement. Sometimes excavation for a basement is deep enough to get below frost line, or to bedrock itself, it depends greatly on the region. "Reasonable cost" is kind of a subjective thing, but I'd say starting with a a good foundation is a bare minimum of requirements for what would end up qualifying as "constructed properly", so at least as far as I'm concerned this is an absolute requirement.
- patentatt 5y ago
  I'm still confused. Basements go below frost line, sure, but bedrock can be hundreds of feet below the surface. I don't know of any home I've ever seen that has piles driven down to bedrock. Is this just a regional thing? What am I missing here?
  - tristor 5y ago
    Yes, bedrock can be many hundreds of feet below the surface, and in other areas bedrock can be pretty near to the surface. This is one reason why you should have a geologic and structural engineering report done on a plot before you build (and arguably before you buy the plot). Depth to bedrock greatly factors into the cost if you intend to have piles put in to support your foundation. In some areas, it's not actually necessary to drive piles to bedrock to get similar stability, instead piles are driven to refusal at a calculated depth based on the expected foundation load. In the regions I'm planning to build though, bedrock is nearer to the surface (or in some cases exposed above the surface as an outcropping), which means that the proper way to do things is to drive piles to bedrock. I am not a structural engineer, and I don't know what is necessary where you live, my list was made for my specific purposes and shared because it was asked, it's not an argument in favor of any specific structural techniques, you should speak to a structural engineer in your area.

tristor 5y ago

The answers to your questions definitely vary by region. If you're building a house, one of the first things you should do is get a structural engineer's assessment of the lot before you plan the foundation, because soil type, bedrock depth, freeze lines, environmental concerns, etc. all affect this. But yes, it's fairly common to do this if you care about structural integrity over the long term. In areas with soil type that support it, it's more common to do simple slab foundations without footings, but in most of the US footings are used and the foundation is built as part of a crawl space or basement. Sometimes excavation for a basement is deep enough to get below frost line, or to bedrock itself, it depends greatly on the region. "Reasonable cost" is kind of a subjective thing, but I'd say starting with a a good foundation is a bare minimum of requirements for what would end up qualifying as "constructed properly", so at least as far as I'm concerned this is an absolute requirement.

patentatt 5y ago
I'm still confused. Basements go below frost line, sure, but bedrock can be hundreds of feet below the surface. I don't know of any home I've ever seen that has piles driven down to bedrock. Is this just a regional thing? What am I missing here?
- tristor 5y ago
  Yes, bedrock can be many hundreds of feet below the surface, and in other areas bedrock can be pretty near to the surface. This is one reason why you should have a geologic and structural engineering report done on a plot before you build (and arguably before you buy the plot). Depth to bedrock greatly factors into the cost if you intend to have piles put in to support your foundation. In some areas, it's not actually necessary to drive piles to bedrock to get similar stability, instead piles are driven to refusal at a calculated depth based on the expected foundation load. In the regions I'm planning to build though, bedrock is nearer to the surface (or in some cases exposed above the surface as an outcropping), which means that the proper way to do things is to drive piles to bedrock. I am not a structural engineer, and I don't know what is necessary where you live, my list was made for my specific purposes and shared because it was asked, it's not an argument in favor of any specific structural techniques, you should speak to a structural engineer in your area.