peir foundation

Started by Simon b, March 07, 2005, 09:04:20 PM

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Simon b

Jon..

bought your plans last yr and will be moving in next weekend (14x24 ) I live in washington state,
(northern,costal comunity) ,I didnt go the permits route as the wait list was a long one. My question is  .(and I relize you cant know for sure ) but can a pier foundation be passed in wash. ( or do u think a requirement will be to put a foundation in)  ..I'm semi thinking of turning myself in as i will be bringing electricity on the property soon and will need a permit to hook up ....  any thoughts?

jraabe

#1
The primary concern in Western WA is that we are in a high potential earthquake zone. Because of that foundations need to be tied into the ground and up into the walls and roof more than they are in most other areas of the country.

That said, there are ways to reinforce post and pier foundations to meet these requirements. Often it involves things like extra metal straps up into the wall sheathing and perhaps a bit heavier on the wall sheathing.

Post and pier foundations probably are more likely to be required to have an engineering analysis  than would the same house with a full perimeter concrete foundation.

DYNAMIC LOADS:

Standard plans and most beam and span tables are engineered for the DOWNWARD loads that are at work on a building for 99.999% of its lifetime. When big dynamic loads (sideward and up and down motion that come with unusual events such as hurricanes and big earthquakes) happen, how the building performs is both much more complex and to some extent unknowable.

However, after every earthquake or hurricane engineers pour over the wreckage assessing what did and did not work to hold things together. They then use these tricks and learned analytical models to predict how future buildings can be inexpensively made to withstand such forces.

Not only foundations, but the slope and soil at the site, window size and location, the height of the building and even where it sits on a lot goes into the calculation of these loads. This is something that needs to be done for each specific project.

I think such an analysis by a practical and up-to-date local engineer is good insurance. (Workups on most of my local custom projects cost about $300.)

An engineering review can carry a lot of the burden of convincing an inspector to approve your building permit. And it will help you sleep better as well.

Such an analysis can even be done after the buidling is up as many of the straps and holddowns can be retrofitted later if needed.