How to Build an Extension on a Trailer

Trailers that are set up at trailer parks can be double-wide and single-wide models. If you have a single-wide trailer you can add an extension to increase the square footage or living area. You can do this by adding a sun-room or patio-room to the trailer. Determine a size for the extension and then obtain costs for the materials.

Build an extension on an existing trailer to add more room.

Step 1

Measure the width and depth for the trailer extension with the tape measure. Note this measurement on a piece of paper. Hire a contractor to excavate the area where you want to build the extension and pour the concrete pad.

Step 2

Measure pieces of 2-by-4 to the width, depth and height for the extension. Cut the 2-by-4 boards to these measurement with a circular saw.

Step 3

Construct modular frame sections with the cut pieces of 2-by-4 boards. Build these sections to a width of 4 feet. Secure the boards in the shape of a rectangle with nails using a nail gun.

Step 4

Set the modular frame section along the perimeter of the concrete pad. Attach each section of framing with nails.

Step 5

Drive nails into the 2-by-4 on the perimeter of the concrete pad with the ramset. This is a tool that uses a 22-caliber cartridge to fire a nail into the concrete.

Step 6

Place a 2-by-4 board at the top of the exterior wall of the trailer. Secure the board to the studs using the nail gun. This is a ledger board that will be used for the roof.

Step 7

Measure and cut pieces of 1/2-inch plywood to the depth of the trailer extension. Place these pieces of plywood on the ledger board and on top of the wood frame. Secure the plywood with nails.


  • Outside structures added to a trailer or other building may require a building permit.