What are the requirements for a foundation for a wooden house? They are nothing specials, i.e., not very different from the requirements for a traditional brick & mortar house foundation. A wooden house is lighter, but we don’t think that makes a lot of difference for the foundation itself. For us, as wooden house builders, there are three requirements: the foundation should be flat, it should let us anchor the house firmly, and the pipes and guides for water and electricity should be at the exact right spot.
That a foundation should be flat is logical: if the foundation is at an angle, your house will be at an angle. But also the foundation should not have any serious “waves”, it should be very plain with minimal height differences, say max five millimeters. You can check the flatness of a foundation with a laser, but a little rain can be very helpful at no cost: the rain water should spread evenly over the foundation and you should not see any deep puddles or pools.
A wooden house must be anchored solidly. Wind can generate enormous forces and the anchoring must prevent your house from being blown of the foundation. Calculating the exact anchoring is a job for highly specialized engineers.
And then finally: the exact positioning of guides and pipes and cables for water and electricity. If the downpipe for your toilet is 10 centimeters off, suddenly your toilet will be placed 10 centimeters into the bathroom. In our experience the exact positioning of guides and pipes and cables is something that could do with a little more attention. Too often we have seen downpipes coming up on the wrong side of a wall, or even exactly under a wall, and we have seen electricity popping up exactly in front of a front door. All these things can be fixed, but it would be so much easier to have it done correctly right from the beginning.