Here is why. Regardless of what other plan companies provide, one thing we learned since having an Internet Web Presence for over 10 years, is not everybody’s method on how a basement is to be constructed is the same. There are so many structural variables, from one state to another, from one city to another, it seems no matter what we do, in no way can we design a basement plan to please every building inspector or building contractor. On top of that, there are so many different materials to choose from today. You can choose ICFs, CMUs, poured concrete walls or even wood foundation walls. The framing of the floor has about a dozen different types of materials from “2 by” lumber to engineered trusses. And if you’re in a high seismic zone, all the rules change. There is absolutely no such thing as a “One Size Fits All” Basement Plan.
Here is what we recommend
Even if you do not buy your house plan from us. Have a local qualified structural engineer who is knowledgeable with the most common methods allowed for your area, test your soils and design your foundation especially for your lot situation. It will cost you from a couple of hundred to maybe a couple of thousand dollars depending on the situation and complexity of the design. In the long term scheme of things, you will have a happier life having the most important part of your new home structurally engineered the correct way.
What we do provide
We do provide, what here in north Texas, is commonly known as a FHA type “C” slab on grade foundation plan. In short, a “C” slab is a 5 inch thick 3,500 psi monolithic slab, #3 rebar at 12″ on center in two directions. The perimeter beam is 10″x24″ and has 4-#5 bars, 2 top and 2 bottom. The interior beams are also 10″x24″ with 4-#5 bars and are spaced no more than 12′ apart. There is a minimum of 4″ of sand or gravel cushion fill and a 4 mil poly vapor barrier beneath the entire area of the slab. Back in the 1970s, this foundation was “cookbook” engineered by HUD for the expansive soils in north Texas with a plasticity index not exceeding 45.
Never-the-less, most city plan reviewers here in north Texas requires that all foundations be designed by a licensed professional engineer.