The present invention provides an impact resistant sheet material that
helps provide exterior walls of a building with resistance to impacts so
that the building structure can meet building standards, such as the
Miami-Dade County Large Missile Impact Test, for resisting impacts in
high wind areas. In one embodiment, sheet material comprises an impact
resistant layer that attached to fibrous substrate. The impact resistant
layer provides impact resistance to the sheet material so that a wall
structure employing the sheet material is able to successfully withstand
an impact from a projectile comprising a 9 pound, 7 foot two-by-four
("2.times.4") traveling at a speed of at least 34 miles per hour. The
impact resistant sheet material may comprise a moisture vapor permeable,
water-impermeable barrier layer having a hydrohead of at least 55 cm and
a moisture vapor transmission rate of at least 35 g/m.sup.2/day. Such a
sheet material is particularly useful in barrier applications, such as a
house wrap.