12-07-2009, 07:24 PM
Mark P gave a good explanation as to why a rafting pad is used.
Sorry… I wasn’t watching the thread for a few days there.
Rafting is unfortunately thought a generalized term these days and nearly lost is it's origin meaning but when properly used, it indicates connectedness (in a boating situation, a cluster of boats may “raft” (tie) to one another “rafting” from the the Old Norse meaning to Tie and or Connect to one another many members) and such a pad should not be considered a floating or spreading load pad, in the case of a house, we’re talking about rafting the posts and or footings to one another through a concrete pad thus deemed a “rafting pad” and not a garage pad/slab or turndown footing pad/slab.
A grade beam is typically a concrete reinforced beam established at grade level and serves as a foundation. Such beams may be established under several differing circumstances. A typical established grade beam might be placed atop piles spanning from one pile to another along the ground hence “grade”. There are other scenarios also. Sometimes the ground may be too soft or subject to light flooding and there are a handful of other reasons for this too but most deal with soil conditions.
Is there a way to keep the house together under a seismic event? Certainly.
Hawaii isn't really known for heavy earth quakes moderate perhaps but certainly not heavy. The current seismic regulations in the IBC are more than adequate for Hawaii; winds are a greater concern in Hawaii.
What's the grade slope(ground angle) of your house location Dennis? Will you be creating a flat level area for the house or are you on a slope? You've already stated you're going to rip and roll the aa so I'd gather there's no critical slope. If you can level your house footprint area you should be able to rely on a simple rafting pad for your post footings to be tied to one another if you have deep earthquake concerns.
I opted for a slab garage with turn down footing perimeter to serve as my houses main foundation. Everything will be built atop and over hanging to a degree above that. I specified a 55" high storage vault above the garage putting the first main occupied space at 15' above grade to provide some additional security with the only exterior decks on the next floor above at 25' above grade. All of that was to establish an ocean view and provide some additional security to the house along with minimizing the rafting pads necessary etc. I’m trying to kill a bunch of birds with one stone so to speak.
E ho'a'o no i pau kuhihewa.
Sorry… I wasn’t watching the thread for a few days there.
Rafting is unfortunately thought a generalized term these days and nearly lost is it's origin meaning but when properly used, it indicates connectedness (in a boating situation, a cluster of boats may “raft” (tie) to one another “rafting” from the the Old Norse meaning to Tie and or Connect to one another many members) and such a pad should not be considered a floating or spreading load pad, in the case of a house, we’re talking about rafting the posts and or footings to one another through a concrete pad thus deemed a “rafting pad” and not a garage pad/slab or turndown footing pad/slab.
A grade beam is typically a concrete reinforced beam established at grade level and serves as a foundation. Such beams may be established under several differing circumstances. A typical established grade beam might be placed atop piles spanning from one pile to another along the ground hence “grade”. There are other scenarios also. Sometimes the ground may be too soft or subject to light flooding and there are a handful of other reasons for this too but most deal with soil conditions.
Is there a way to keep the house together under a seismic event? Certainly.
Hawaii isn't really known for heavy earth quakes moderate perhaps but certainly not heavy. The current seismic regulations in the IBC are more than adequate for Hawaii; winds are a greater concern in Hawaii.
What's the grade slope(ground angle) of your house location Dennis? Will you be creating a flat level area for the house or are you on a slope? You've already stated you're going to rip and roll the aa so I'd gather there's no critical slope. If you can level your house footprint area you should be able to rely on a simple rafting pad for your post footings to be tied to one another if you have deep earthquake concerns.
I opted for a slab garage with turn down footing perimeter to serve as my houses main foundation. Everything will be built atop and over hanging to a degree above that. I specified a 55" high storage vault above the garage putting the first main occupied space at 15' above grade to provide some additional security with the only exterior decks on the next floor above at 25' above grade. All of that was to establish an ocean view and provide some additional security to the house along with minimizing the rafting pads necessary etc. I’m trying to kill a bunch of birds with one stone so to speak.
E ho'a'o no i pau kuhihewa.