You want to control the weeds in your yard or garden in an efficient and affordable way. You have heard that some people use tar paper (the roofing material) to block the weeds. But is this safe?
Tar paper does not pose any environmental concerns when used for its intended purpose (under shingles on a roof). But it is made with tar (or asphalt), which is at the bottom of the barrel in the petroleum refinement process. To be safe, do not use it around food-producing plants (like vegetable gardens or fruit orchards).
Tar paper will prevent weeds from growing by blocking any sunlight from reaching them. Since it is designed to be a water barrier for roofing, it will also tend to cause water to pool -- not the best quality in a landscaping fabric. Professional landscape fabric (sometimes called weed barrier) stops the weeds while allowing water to pass through.
A quick comparison between the cost of tar paper and good quality weed barrier shows that tar paper is less expensive. But with the extra money spent, a good landscaping fabric will out-perform tar paper without any worry of contamination.