Permeable Seamless Roof Surface

The top layer is the actual paving material.

Permeable seamless roof surface.

Permeable surfaces also known as porous or pervious surfaces allow water to percolate into the soil to filter out pollutants and recharge the water table. Other types of roofing including cedar shingles and concrete tile roofing are fairly permeable. In this particular job the roof is vented. Consider permeable paving in large walkways or driveways and make sure that a 6 inch gravel bed is immediately below the porous material.

From the top down there are four layers to permeable paving. Any moisture driven up from the attic will condense on the underlayment underside. Many types of roofing including epdm and standing seam steel roofing are virtually impermeable to water vapor. With the new seamless barrier.

Regardless of your roofing underlayment choice your insulated roof assembly will not dry to the exterior unless the roofing is vapor permeable. A breathable 34 0 perms but waterproof membrane like siga majcoat membrane and elevating the standing seam metal roof off of the decking to allow any water than may be in the osb sheathing to dry. After all water can gather under an existing roof surface and then over time erode and ruin the roofing components underneath the surface layer. The new standing seam metal roof is to be installed over the existing 1x4 skip sheathing so no solid roof deck.

Impermeable impervious surfaces are solid surfaces that don t allow water to penetrate forcing it to run off. Seamless roof coating solutions take care of this immediately though in many cases. Even smaller roof leaks can lead to bigger problems if they are left untended. Each of these different layers acts as a filtration system to clean storm water.

Asphalt shingles are a little bit permeable in windy conditions but not very.