Most have a reinforcing sheet of polyester to prevent puncture, increase wind-load resistance, and improve dimensional stability. This layer is not necessary for some applications. There is a range of attachment methods, depending on the location of the roof and the type of membrane. Sheets of membrane are mechanically anchored, chemically adhered, or ballasted. With mechanical attachment methods, clips and metal plates, batten strips, or bars, are used.
Fasteners secure the sheets at the seam edges.
If there are not enough fasteners, the wind uplift can cause the fasteners to eventually work loose. A conservative fastening schedule is normally advised. Chemically adhered membranes use adhesives to hold the membranes to the roof substrate. The time and labor to apply the adhesive and smooth the sheets in place adds to the cost of the job, but the bond achieves a roof that is highly resistant to wind, water, and dimensional changes. Ballasted roofs weight the membrane with gravel or pavers.