3 More Important Layers Of Your Roof |

3 More Important Layers Of Your Roof

graphic with the quote "3 More Important Layers Of Your Roof"

If homes came with parts manuals, those instructions would take thousands of pages. For example, your central Ohio home’s roof is not a single piece but a group of parts connected together to function as a water-resistant shield over your home. Three necessary layers of the shield are the roof deck, ice and water shield, and underlayment.

Roof Deck

Your home’s attic has a “floor” of joists and a “ceiling” of rafters. These wooden support members connect the walls of your house (joists) and hold up your roof (rafters). Your roof deck comprises the rafters and sheathing. They are the foundation layer for your finished roof

The rafters are spaced closely enough to bear tremendous weight, which they transfer to your walls. The rafters are cut at angles to allow your roof to have a pitch, or steepness, perfect for shedding the worst of Ohio’s snow, rain, and ice storms. 

Atop the rafters are sheets of plywood or oriented strand board (OSB) that stabilize the rafters and allow just about any roofing material to be installed on them. These sheets of thin veneered wood (plywood) or glue and chips (OSB) are purposely nailed into place with small gaps to allow for thermal expansion. Otherwise, your roof would buckle. 

For your roof to last a long time and stay healthy, your roof deck must be strong. It is always part of an annual roof inspection. If necessary, defective rafters can be sistered (a second rafter attached beside the original) or replaced without disturbing the roof. 

Sheathing is usually replaced in a complete roof replacement. Your roofer’s Scope of Work and estimate may include a certain number of sheets as part of the final cost, with additional sheets specified at a given market price. Reasons to replace sheathing include:

  • Mold
  • Physical damage
  • Rot
  • Insect or pest invasion

Your roofer is best qualified to assess the condition of your roof deck. 

Ice and Water Shield

Ohio’s winters are not to be trifled with, so every roofer installs ice and water shield along the bottom edge of a roof, either at original installation or during full roof replacement. This thick, self-adhesive, spongy material seals around nail and staple holes, does not allow water to penetrate, and helps combat water infiltration from ice dams.

Ice and water shield is also laid down along valleys and (sometimes) over hips. Valleys and hips are two places the different planes of roof sections meet. Anywhere leaks might find a way into your home, ice and water shield can be installed to prevent them. 

Your roofer can tell, just by peering at the bottom edge of your finished roof, if you have this vital layer on your home’s roof. 

When looking at full roof replacement, ice and water shield should be replaced. Its self-adhesive back is very sticky, and its spongy, self-sealing qualities do not degrade with age. Unless sheathing is replaced, expect the ice and water shield to remain.


Your roof deck is covered in rolled material called underlayment. This thin, stapled material helps seal around nail and staple holes and is either synthetic or organic felt. 

Underlayment is waterproof; shingles are designed to be water-resistant. Sheathing and joists are neither waterproof nor water-resistant. Underlayment is yet another barrier against water damage to your Ohio home. 

When having your entire roof expertly replaced by highly skilled roofers, expect the old underlayment to be removed and replaced with fresh underlayment. 

In Unison

Your Ohio home’s roof deck, ice and water shield, and underlayment form the bottom of your entire roofing system. They work together to give your roof the firm footing it needs, plus offer excellent water protection. 

The only layer you, the homeowner, can safely view is the roof deck, and there you will be looking at its underside. A trip into the attic should satisfy your curiosity. The angled timbers above are rafters; the wide expanses of wood between rafters are sheets of sheathing. 

Tell your roofer right away if you see discoloration, water stains, rot, or evidence of pests chewing or boring into the wood. 

First Things

Since your roof deck is part of your home, you can expect it to be put in place even if you are installing a brand-new roof.

If you are having full roof replacement performed, the roofing crew will tear off your old roof down to the sheathing before adding new layers. This exposes the deck so they can inspect it for rot or other water damage. Always insist on fresh underlayment and ice and water shield to give your home maximum protection.

When you trust your house to Allstate Exteriors & Restoration in central Ohio or Cape Coral, FL, your roof, home, and family are all protected. Contact us today to learn about our extensive roofing, siding, and gutter installation services.