Modifying duplex home plans typically involves a cost. The amount varies depending on whether the modification is a minor change that can be made directly on the blueprint or a larger alteration that requires redrawing the plan.
Making minor changes to a duplex home plan is called redlining as it involves making corrections in red ink directly on the blueprint of the home. Larger changes, such as those with the potential to affect the structural integrity of the house, must be done by editing the computer-assisted design file of the home. In order to do this, the person doing the editing must have access to a copy of the file and permission to make changes.