Build a complete or partial cinder block foundation to accommodate the master bedroom. Dig down to solid ground to pour a concrete footing around the perimeter of the space. Have brick masons install a cinder block foundation 4 to 6 feet in height. Leave a crawlspace door to work inside the crawlspace. Install under the floor of the new room plumbing for a bathroom in the master suite and some electric wiring.
Enlist carpenters to lay a solid framework around the foundation. Create the complete framework including roof area. Carpenters will need to install wall studs every 18 inches around the perimeter of the new bedroom. Decide where windows will be placed. Cover the entire exterior of the new space with exterior grade masonry. Install windows and caulk. Paint appropriate areas on the exterior of the new space.
Cover the roof with plywood and install asphalt shingles. Install guttering and downspouts with splash blocks to carry rain away from the new addition. Cut through the side of the mobile home exterior to build a doorway into the suite. Finish both sides of the entryway to harmonize with the decor.
Frame all interior walls and a bathroom area in the master suite. Run plumbing drains and pipes for the bath. Install insulation in all interior walls. Build in the ceiling with drywall over ceiling joists. Place plenty of fiberglass roll insulation in the ceiling area. Run electrical wiring for light fixtures and outlets. Install paneling or drywall on the walls.
Lay wooden flooring, tile or carpet in the master suite. Place a bathroom vanity and tub. Lay flooring in the bath area. Install baseboard material and trim in all areas of the suite. Hook up light fixtures and electrical outlets.