The least expensive way to construct a screened-in porch is to start with an existing foundation such as a deck or patio. Screening in an existing porch is a relatively easy job for the do-it-yourselfer and requires limited carpentry skills. Due to the little amount of carpentry needed to screen-in a porch or deck, the cost is generally lower than building from scratch. Kits are also available to enable you to screen-in a porch in the simplest manner.
Check with your local zoning authorities to see if you will need a building permit to complete the job. Generally, a permit is not needed to screen-in an existing porch. However if building from scratch it is important to check the legalities before starting.
Sketch out a blueprint of your porch or deck to determine what materials are needed to accomplish the project. This plan should include a basic drawing to scale and the true measurements of the starting foundation.
Create a knee wall by installing exterior siding from the railing down to the flooring of the existing porch or deck. Use 8d nails to fasten the siding to the posts. It may be necessary to erect additional posts, depending on the size of the panels.
Use 20 by 20 mesh to encompass the areas to be screened-in. The number of holes per square inch determines the mesh size. Common mesh for screens is 18 by 14, which will keep out common insects. However the smaller mesh of 20 by 20 will protect against even the tiniest of insects.
Measure the distance between existing columns and any additional columns that may need to be installed. Consider purchasing a screen frame kit to make the project easier and avoid the added cost involved in building your own framework. Kits are usually available in a number of standard sizes to fit the distances between the deck columns. Stain or paint the framework and columns as desired.
Attach the screen frames to the columns using 2-inch exterior deck screws. Attach any trim as necessary, again using exterior deck screws.
If you are more skilled with carpentry and elect to build your own frames and stretch the mesh fabric to fit, consider recycling old screen doors. This will cut down on the cost of doing your own framework.