The header joist underneath my sliding glass door is rotted in a 6 foot section. The rotting ranges from 10% in some spots to 50%. There is also a cement step that is in the way of removing this header joist. My question is do I add additional support from inside the house and spray some form of protection on the header joist to stop the wood fom rotting or do I remove the cement step, then replace the header joist, or ???. I am currently having vinyl siding put on my home and this is a 2 story home. Thanks.