If you are lucky enough to live in or near a wooded area, chances are your children have talked about building a tree house. Building a simple, yet functional tree house for your kids to enjoy does not have to be a difficult project to undertake; you can build one with a supply of 2-by-8-inch and 2-by-4-inch cedar boards. Look around your yard for the perfect tree in the right location and surprise your kids one day with their own backyard tree fort.
Locate the site for your tree house within a perimeter of trees sturdy enough to support the deck, where there is enough space within the perimeter to accommodate its size.
Use 2-by-8-inch cedar boards to frame the deck that will support your tree house. Cut the boards to the desired length and width for the deck. Lay the first board horizontally between two of the perimeter trees and connect the boards to the trunks of the trees with lag bolts. The height at which you attach the boards will determine the height of the deck.
Attach the second and third boards at a right angle to the first, connecting one end of each board to the same tree trunk to which the first board is bolted. Secure the other end of the boards to another tree trunk. Attach the fourth board perpendicular to the two boards just used, bolting it to the same two trees to complete the deck frame. When finished you should have a square or rectangular outline built with four boards around the perimeter of the trees.
Measure the width between the inside edges of the deck frame and cut the cedar boards to that length. Slide the 2-by-8-inch boards horizontally between the boards of the deck frame at 18-inch intervals, and secure them to the deck frame at both ends with galvanised roofing nails from a nail gun. These horizontal beams will act as floor joists to support the floor and the tree house structure.
Measure the length from one corner of the deck frame to the opposite corner and cut a piece of 2-by-8-inch cedar to that length. Position the board underneath the deck frame, flush with the bottom side of the floor joists, from one corner to the opposite corner. Secure the board to the tree trunks at each corner with lag bolts, and insert nails at the joint of each floor joist for extra support.
Lay the pressure-treated plywood panels flat on the deck and secure them to the floor joists with a nail gun and galvanised roofing nails. You may need to trim away some excess plywood on the edges of the deck frame.
Assemble a square frame for the top and bottom of the tree house by making two squares out of four 2-by-4-inch cedar boards each. The eight boards used to build these square frames should be equal in length and should measure the desired width of the tree house. Secure the joints with galvanised roofing nails.
Lay the bottom frame flat on the deck and set one 2-by-4-inch board upright in each of the four corners of the frame; secure the joint with galvanised roofing nails. The length of the vertical 2-by-4 boards should be equal to the desired height of the tree house walls. Set additional 2-by-4-inch boards upright at 18-inch intervals around the edges of the frame and nail them in place. Lay the top frame on top of the vertical boards, aligning the edges, and secure all joints with galvanised roofing nails. You may need a ladder and some assistance to complete this step.
Cut additional pieces of 2-by-4 inch boards to frame the roof of the tree house. These boards should be equal to or a few inches shorter than the width of the tree house. Position the boards along the edge of the top square frame at an angle on two opposite sides of the tree house to form a triangle shape and attach them with galvanised roofing nails. Connect the top edges of the angled boards to a horizontal piece of 2-by-4-inch cedar measuring the width of the tree house.
Cover the walls and roof of the house with pressure-treated plywood panels. If you would like to have windows in the walls of the tree house, frame them first with 1-by-2-inch cedar boards, and cut the plywood panels to fit around the frame. Secure the plywood panels in place with galvanised roofing nails from a nail gun.
Cut 2-by-4-inch cedar boards to 3½-foot lengths and secure them to the deck at 12-inch intervals by positioning them vertically against the outer deck frame. Line up the bottom of each 2-by-4-inch board with the bottom of the deck frame and secure them in place with galvanised roofing nails. Leave a 2-foot opening somewhere along the perimeter to install a ladder or rope by which to access the tree house.
Measure the length of each side of the deck frame and cut pieces of 2-by-4-inch cedar to those lengths. You may need to cut two shorter pieces for the side of the deck where the 2-foot opening is positioned and, if you positioned your tree house structure against the edge of the deck on one side, you will need two boards for that side, as well. Lay each 2-by-4-inch board flat on top the vertical boards on the corresponding edge of the deck frame to form a railing. Secure the horizontal 2-by-4-inch boards to each vertical board with galvanised roofing nails.
Finish the tree house by painting it with exterior-grade paint. Stain the deck and railing, if desired, wiping away the excess stain with a soft cloth. Allow the paint and stain to dry for at least 48 hours, then install a ladder or rope to access the tree house. Install two screw eye hooks on either side of the 2-foot opening, and hang a rope ladder or lean a wooden ladder against the opening, bracing the legs on the vertical railing boards.