Originally Posted By: Ray Joseph This post was automatically imported from our archived forum.
Hi, I’m hoping the experts here can give me some advice.
We are putting a one story addition on our house, floor level on the portion of the house that is getting the addition sits about 2.5-3 feet above the outside gound level. Some of the contractors we have talked with have recommended a wood foundation versus a concrete foundation. I guess the wood foundation is similar to a deck and is cheaper than a concrete foundation which would have to be built up 2.5-3 feet. They also suggested since we have a slight grade in the backyard toward the area where the addition will be located that by using a wood foundation we forgo any drainage work that would have to be installed if we used a concrete foundation.....of course if we want to pay the extra for a concrete foundation they'll do it but they say that a wood foundation will suffice and is in code for a one level addition..I'd be thankful for any advice, of course I'd love to save the money but I want to make the decision based on what works and not what would be cheaper...
Originally Posted By: Mark Dudley This post was automatically imported from our archived forum.
If your existing structure uses a concrete foundation, I would go with concrete. It is very important that the new addition move the same as the existing structure.
Many homes are built off grade, building on concrete is actually a fairly recent (15-20 years or so) method of building.
Crawl space access can be a good thing, especially if attic access is limited.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
You are asking about design decisions that should be referred to an engineer or architect, and not home inspectors. Wood foundations can be economical under limited conditions, but there may be moisture/durability concerns. It may be a good option, or contractors may be pushing that option to maximize profit.
There are many issues and concerns with additions and foundation types that should be referred to a design professional. State laws restrict design services, and you may need stamped plans to pull a building permit anyway. They charge a small fee compared to the cost of construction, and you get an independent professional opinion and design.
Just my opinion and 2-nickels ... 
-- Robert O'Connor, PE
Eagle Engineering ?
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I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: rcloyd This post was automatically imported from our archived forum.
I agree with Robert. A licensed design professional is the way to go. They can look at the existing conditions on your lot and recommend the best foundation type.
Originally Posted By: mkober This post was automatically imported from our archived forum.
As usual, Robert’s advice is right on the money, and I agree whole-heartedly. Your comment regarding drainage has me baffled, however–regardless of the foundation type, you do NOT want natural drainage/surface water flowing towards your foundation. You are asking for trouble down the road unless a concerted effort is made to divert the natural flow of water away from your house and addition.
Originally Posted By: cfuoco This post was automatically imported from our archived forum.
Hello Ray. Correct me if I am wrong but I think there might be a misunderstanding. Are you talking about a below grade wood foundation or the addition being built like a deck where there are concrete piers into the ground supporting girders and joists and the structure being built on that?
Originally Posted By: Ray Joseph This post was automatically imported from our archived forum.
Carmine, you have it right when you say that is is an addition being built almost like a deck I guess. Everything is above grade. I posted not really loking for enginerring advice, but for advice from home inspectors, the folks that I figured would have seen a number of addititons like this and could offer an opinion of their durability etc…what issues or non-issues that may or may not have been seen by home inspectors. Thanks for any advice