Membrane roofing

1. A construction underlayment comprising

a rigid foam board having two broadest sides defining a thickness therebetween; and

a reinforcing facing comprising

a flexible resin membrane bonded across one of the broadest board sides and an array of touch fastener elements extending from the membrane and exposed for engagement, the touch fastener elements having individual resin stems extending integrally from a surface of the membrane and molded heads defining overhangs for engaging fibrous loops; and

a fibrous tie layer between the membrane and the foam board;

wherein the tie layer includes a reinforcing scrim, wherein the scrim has fibers at least partially embedded in resin of the membrane and formed of a material selected to inhibit chemical bonding between the scrim fibers and the membrane resin.

2. The construction underlayment of claim 1 , wherein the facing extends across an entire lateral extent of the board.

3. The construction underlayment of claim 2 , wherein the array of touch fastener elements covers substantially all of one of the broadest board sides.

4. The construction underlayment of claim 1 , wherein the foam board defines foam knit lines extending along a length of the board between adjacent foam portions, and wherein the tie layer includes fibers disposed across the knit lines.

5. The construction underlayment of claim 1 , wherein the tie layer is adhered to the foam board.

6. A roof comprising:

a roof deck;

underlayment secured to the roof deck, the underlayment comprising

a rigid foam board having two broadest sides defining a thickness therebetween; and

a reinforcing facing comprising

a flexible resin membrane bonded across one of the broadest board sides and an array of touch fastener elements extending from the base membrane and exposed for engagement, the touch fastener elements having individual resin stems extending integrally from a surface of the membrane and molded heads defining overhangs for engaging fibrous loops; and

a fibrous tie layer between the membrane and the foam board;

wherein the tie layer has fibers partially embedded in resin of the membrane; and

a flexible roof membrane extending over the underlayment, the roof membrane comprising a water-impervious sheet with a field of fastener elements exposed on an underside thereof and engaged with the fastener elements of the underlayment to secure the roof membrane.

7. The roof of claim 6 , wherein the fastener elements of the underlayment and the fastener elements of the roof membrane form a fastening with a nominal shear slack of between about 0.762 mm (0.030 inch) and 1.524 mm (0.090 inch).

8. The roof of claim 6 , configured to withstand an up-lift force of at least about 4.309 Newton/square meter (90 pound/square foot).

9. The roof of claim 6 , configured to withstand an up-lift force of at least about 0.022 Newton/hook (0.005 lbf/hook).

10. The roof of claim 6 , wherein the underlayment is secured to the roof deck by engaged touch fasteners.

11. The roof of claim 6 , wherein the underlayment is secured to the roof deck in part by washers having touch fastener elements for engaging touch fastener elements on the roof membrane.

12. The roof of claim 11 , wherein the washer includes a peripheral anti-peel flap having fastener elements for engaging fastener elements on the roof membrane.

13. The roof of claim 6 , further comprising ballast secured to an upper surface of the membrane by touch fastener elements.

14. The roof of claim 6 , further comprising multiple layers of underlayment, wherein a lower layer is secured to the roof deck via through fasteners and an upper layer is secured via one of touch fastener elements and adhesive.

15. A method of roofing a structure, the method comprising:

securing underlayment to a roof deck, the underlayment comprising

a rigid foam board having two broadest sides defining a thickness therebetween; and

a reinforcing facing comprising

a flexible resin membrane bonded across one of the broadest board sides and an array of touch fastener elements extending from the base membrane and exposed for engagement, the touch fastener elements having individual resin stems extending integrally from a surface of the membrane and molded heads defining overhangs for engaging fibrous loops; and

a fibrous tie layer between the membrane and the foam board;

wherein the tie layer has fibers partially embedded in resin of the membrane;

positioning a flexible roof membrane to extend across the underlayment, the roof membrane comprising a water-impervious sheet with a field of fastener elements exposed across one face thereof to engage with the fastener elements of the underlayment to secure the roof membrane; and

mechanically enhancing engagement of the fastener elements of the flexible roof membrane and underlayment.

16. The method of claim 15 , further comprising:

providing a slip sheet between the underlayment and the flexible roof membrane to prevent engagement of the respective fastener elements of the underlayment and roof membrane;

adjusting the positioning of the flexible roof membrane over the underlayment; and

moving the slip sheet to allow engagement of the fastener elements of the flexible roof membrane and underlayment.

17. The method of claim 15 , wherein mechanically enhancing the engagement of the fastener elements comprises rolling or brooming the outer surface of the positioned membrane.

18. A construction underlayment comprising

a rigid foam board having two broadest sides defining a thickness therebetween; and

a reinforcing facing comprising

a flexible resin membrane bonded across one of the broadest board sides and an array of touch fastener elements extending from the base membrane and exposed for engagement, the touch fastener elements having individual resin stems extending integrally from a surface of the membrane and molded heads defining overhangs for engaging fibrous loops; and

a fibrous tie layer between the membrane and the foam board;

wherein the tie layer has fibers partially embedded in resin of the membrane.

19. A construction underlayment comprising

a rigid foam board having two broadest sides defining a thickness therebetween; and

a reinforcing facing comprising

a flexible resin membrane bonded across one of the broadest board sides and an array of touch fastener elements extending from the base membrane and exposed for engagement, the touch fastener elements having individual resin stems extending integrally from a surface of the membrane and molded heads defining overhangs for engaging fibrous loops; and

a fibrous tie layer between the membrane and the foam board;

wherein the tie layer has fibers partially embedded in the rigid foam board.