One of the most costly and common mistakes made when building a pre-fabricated wooden building is a foundation that is not completely level. With other building methods, like brick or stone-laying, imperfections can be "straightened out" during the building process, but a prefab building requires a perfectly level foundation from the start. Traditional builders may not used to working this way, so its advised to emphasize this need in advance to avoid the extra time, labor, and money needed to fix it later on.