If you want to install vinyl siding over your current wood siding there are some steps to take for preparation. First, check that the wood is in top condition. It can show no signs of mold, mildew, or insect infestation. If there are bad boards in the siding, those must be replaced. Check to see if the wood siding is securely fastened to the studs or wood sheathing. Remove all door and window trim. If the wood siding is beveled or lapped, you will need to install furring strips covered with rigid foam board to provide a level surface on which to install the new siding. A siding installation pro can help you decide whether you need to remove the old siding before installing new.