E X P A N S I O N /CONTRACTION Poly liner will expand as temperature increases and contract as temperature decreases. Do not install poly on a cold day. "Condition" poly and building or equipment at 45° or above (the hotter the better), for 24 hours prior to installation, to minimize expansion. A heated milkhouse or direct sunlight works good (elevate liner off cold floor/ground and unroll for quicker heat absorption).
Allow 1/16" of expansion/contraction per foot (both lengthwise and widthwise for variations from "average" temperature). If installed when temperatures are below the "annual average", allow for more expansion than contraction. When temperatures are above the "annual average", allow for more contraction than expansion. Holes in poly should be drilled up to 1/8" oversize depending on installation temperature.
WHEN TO LAG Manger-liner is not lagged down, but is free to expand without pushing against nail anchors and humping (see "Poly Holddowns" for more information). Conveyor, gutter, and barn cleaner chute liner are fastened only at the intake end of each section of liner, and the sections are overlapped 2" lag front edge of each bottom section only.
For other applications where the liner is fastened at several locations (vs just at intake end of each section), drill oversize or slotted fastener holes. Do not butt sections of liner tightly together. Instead, provide expansion joint 1/16" per foot (silicone caulk to prevent moisture and material from seeping under) on wider joints, some installers will use "shiplap" design.