Residential Roofing Codes: 5 Most Important

1. Ice and Water Shield (IWS)

Sometimes also referred to as “peel and stick”, Ice and Water Shield is a waterproof roof underlayment membrane developed to protect vulnerable areas on a roof from ice and water damage. Ice and water barriers (sometimes called ice and snow shields in cold climates) are made with polymer-modified bitumen.

IWS is one of the most important and the most contested line items in a roofing estimate. The reason that it is so contested is because the building code language is confusing and allows for a lot of misinterpretation. The code language for ice and water shield says "when there is a history of ice damming, you must use IWS..." As you can see, this language is ambiguous leading contractors and adjusters to think that they can find the documentation to argue the history of damming for that roof. However, it is up to the municipality that has authority over the property to determine if it is required on an estimate or not. Because it can be so confusing and hard to find the documents to back it up, we have put IWS as the first line item in our snapshots on the OneClick Code tool including a special PDF document from the city and county saying if they do or do not require IWS on said property.

If you want to read more about IWS and why it costs insurance companies and contractors thousands of dollars each year, you can read more in our blog post, What's Your True Ice and Water Shield Cost? Additionally, if you want a better way to estimate how much IWS you will need for your next job, you can try our free IWS Calculator.

2. Ventilation

Roof ventilation is a system of intake and exhaust vents that provide air circulation to keep the atmosphere inside a home comfortable. Without the in and out passages involved in roof ventilation, hot air will get trapped within your home, causing a variety of problems for your property. For example, without proper ventilation, your home could be riddled with condensation which can lead to mold.

Nevertheless, calculating the right amount of ventilation for a roof can be tricky. With existing ventilation and the need for more ventilation as required by code, you will need to do some complex math to find how much you need and what type. Good news! If you want a better way to estimate how much ventilation you will need on your next job, you can try our free Ventilation Calculator. Made for contractors and adjusters, we want to give you the best tools for the job, for free. We all deserve to work smarter.

3. Sheathing

You might hear roofers use decking and sheathing interchangeably. Sheathing (or decking) refers to the surface that roofing materials adhere to. The sheathing is a large board nailed to the skeleton of the roof so that shingles have a solid base to attach to. A roof’s “skeleton” is made out of rafters or trusses. They are spaced apart anywhere from 16 to up to 24 inches. To bridge these gaps and stabilize these rafters, roofers use a material called sheathing. This holds the roof together and gives the shingles a more stable base to attach to.

The reason that sheathing is so important is that it is not clear if a re-decking is required or not by the municipality for a roofing project. In some cases where nominal lumber was used in the roofing skeleton, a roof might require an entire re-decking to provide more support under the shingles when being replaced. Meaning that the contractor must take out the existing sheathing and replace it with new sheathing. All of this is required (or not required) based on the code that is adopted by the city or county that has jurisdiction over the property.

Why do we not include sheathing on our OneClick Code reports if it is so important? Well, we cannot give our customers a yes/no answer on if sheathing is required because the answer depends on so many variables that we do not know. For instance, the roof type, size, age, and other factors are beyond our understanding of that home. In the future, we would love to provide these answers to our contractors and adjusters. For now, we will give you the roof age and the building code book to get you started.

4. Drip edge

Drip edge is a metal flashing that is installed at the edges of the roof to help control the flow of water away from the fascia and to protect the underlying roofing components. Drip edge overhangs the sides of the roof and has a small metal flange that is bent away from the fascia. Drip edge is important in a roofing estimate and often overlooked. In some states, like Minnesota, drip edge is not required by code. However, if using a GAF Timberline HD shingle, the basic warranty requires drip edge to be installed. This is where our Manufacturer Requirements report comes in handy. Did you know that when a manufacturer requires a line item to uphold their standard warranty, then a contractor is required to put it on and the adjuster is required to pay for it regardless of what the state or city code says about the code item?

5. Valley liner

A lining made of metal protects the valley of a roof from moisture intrusion. You may encounter defective valley-lined shingle installation, failed roll-roofing valley liners, or a cross wash where water running down a roof slope flows across the valley and up beneath the shingles on the adjacent slope. Valley liners are an important component of a roof because most roofs have some valleys and it is important to adhere to the code for the roof to remain in good shape.

Do the right thing

Make sure you check into these 5 line items for every roofing estimate to make sure that you are not missing out on thousands of dollars on your claim. From ice and water shield to drip edge, having the documentation to back up why you included these elements into a roofing estimate can allow you to reduce the back and forth over a claim being paid and get the roof repaired quickly and with the right materials. As always, when you have the right information at your fingertips, you will reduce your headaches over roofing claims. And that is worth its weight in gold.

Frequently Asked Questions

Why is ice and water shield so frequently disputed on roofing estimates?

Because the code language is ambiguous. The IRC says IWS is required where there is a history of ice damming, but it leaves the determination of whether that history exists to the municipality rather than to the contractor or adjuster. That gap means both sides can argue their position, which makes IWS one of the most contested line items on any roofing estimate. The clearest way to resolve the dispute is documentation from the jurisdiction itself confirming whether IWS is required for that property, which is what OneClick Code reports provide.

Why does drip edge matter on an estimate even when local code doesn't require it?

Because manufacturer warranty requirements can override local code on a claim. If a contractor installs GAF Timberline HD shingles, the basic manufacturer warranty requires drip edge to be installed even in jurisdictions where the building code does not. When a manufacturer requires a line item to maintain their warranty, the adjuster is required to pay for it regardless of what the local code says. Skipping it to save on the estimate creates a warranty problem that could cost far more later.

What is roof sheathing and when does a replacement job require re-decking?

Sheathing (also called decking) is the board material nailed to the rafters that provides the structural base for the roof covering. Whether a replacement job requires re-decking depends on the existing sheathing material, the roof type, the age of the structure and what the local jurisdiction's adopted code requires. Older roofs with nominal lumber sheathing may fall below current standards and need full replacement of the deck, while roofs with adequate existing sheathing typically do not. The answer varies enough by property that it requires a jurisdiction-specific check rather than a general rule.

Why do so many roofing estimates go wrong before a single line item is written?

Because they start with the wrong jurisdiction. If you identify the wrong city or county as having authority over a property, which happens 40 to 50 percent of the time when using a postal address alone, every code requirement, sales tax rate and manufacturer specification in your estimate will be off. IWS, ventilation, sheathing, drip edge and valley liner requirements all flow from the jurisdiction, so an incorrect jurisdiction does not produce one error; it produces an estimate that is wrong at every code-dependent line item.