Most mistakes made in designing your own home come from the planning stage. The lack of planning during the planning stage can result in some fairly common mistakes that when revisited by the designer seem rather simplistic. Budgeting is also a big area where common mistakes occur.
Planning Mistakes
Determining which way the home will face on the building site. This is seemingly simple enough but often times over looked. It is important especially if the building site butts up to someone else’s property or to someone else’s home. There are actually building codes in place regarding placement of bathrooms when a home is built next to another one. So the design needs to take into consideration where the home will be placed on the building site. This element also affects where the driveway will be placed, whether there will be road access and whether the entrance to the home will look natural or unnatural.
Another factor to consider is which way the natural light will fall on the house; this will affect heating/cooling costs. Make sure the site is well suited for building before the designing begins, it is no surprise that many pieces of property cannot support the size home desired to be built on it. Every community has building codes ignoring these codes or not knowing them can foil a design plan. So to avoid this common mistake check building codes in the area the home is to be built to insure the design is well suited to meet the codes or requirements of the area.
Not spending enough time on the design is also a common mistake every hour spent designing the home is two hours saved on the building site in corrections. Expect revisions, most home designs goes through a series of revisions before the final plan is drawn up, so spend the time that is needed on the design plan. Make sure that there is an availability of materials for the project. If the home design is for a specific type of constructed home from a semi-exotic material make sure that there is an availability of that material. Not taking into consideration plumbing, electrical, heating and cooling apparatus is also a common design mistake, getting to taken away with aesthetics and not considering the functionality of the space will  expense during the building phase of the project.
Again knowing the codes for plumbing, electrical heating and cooling is important. Check to make sure there are no special requirements for the building site such as if there is a home owners association in the area you intend on building that may have special by laws for that neighborhood. Failing to check with the home owner association (if there is one) can be a huge mistake, some by laws instituted by developments can regulate the size, shape and other factors of what can and cannot be built. Plan ahead and avoid what can be avoided.
Budgeting
Budgeting is another area where common mistakes occur in designing your own home. Budgets cannot be so stringent that there is no room for error. A safe bet is to add $20000 to the budget for errors. Perhaps the $20000 will wind up not being used, but more than likely some of it will be used. Underestimating costs is also a common mistake. To avoid this error overestimate the costs so that when designing your home you will not be put out on a limb financially. Be realistic about the budget so you can avoid common mistakes in designing your own home.