What Is the Right Way to Install a Metal Roof on Top of a Vented Deck?

Are you investing in a standing seam metal roof to replace your shake roof but worried that an inexperienced installer could make hidden mistakes that lead to leaks, condensation, or premature roof failure? Have you received multiple roofing proposals that all seem to promise the same result, leaving you wondering why one roofer is charging so much more?

At RoofSmart, we are one of the very few roofing companies in the area that pay attention to attic ventilation. We have helped hundreds of customers update their ventilation so that it works properly, including building vented decks.

In this case study, we'll show you how we transformed an aging shake roof into a properly ventilated standing seam metal roof, why converting to a vented deck was essential for this vaulted ceiling, and how comparing our proposal to a competitor's revealed critical differences that protected the homeowner from an improper installation.

What issues can a shake roof with a vaulted ceiling have?

Recently, we got a call from a customer that we met at a home show who wanted us to come out and inspect his shake roof with a vaulted ceiling. He knew right away that he wanted some framing updates as well as a new roof.

At first, he wasn’t sure if he wanted metal shingles, Euroshield, or a standing seam metal roof. After discussing the pros and cons of each type of material, the customer decided that he wanted a steel standing seam metal roof.

This customer’s home had an array of issues that needed to be dealt with. Here are the initial problems that I uncovered during my inspection:

• Condensation in vaulted ceiling: One area of the roof had a vaulted ceiling with tongue-and-groove. It had a lot of condensation, which demonstrated that the attic was not ventilated properly. The right way to fix this is to set up a vented deck, which I’ll go over in a different section.
• Chimney repair issues: There was a leaky chimney that required advanced masonry to take apart. This prevented us from installing the proper end-wall flashing on it to protect it from leaks.
• Client initially insisted on doing everything: This client provided CAD drawings for framing and felt that he had to do everything himself. Once I showed him my solution for fixing the problems on his roof and gave him an honest breakdown of how my proposal compared to other roofers’ proposals, he decided to follow my plan.

The shake roof was very old and in poor condition, so it was time to update the roof. He also wanted to extend the roof outward to fill in a small gap in the roof and install a skylight right next to it.

What issues did we fix on this roof?

Aside from installing the new metal roof, there was a lot of work that this roof needed. Here are the main issues that the crew fixed before installing the roof:

• Adding a vented deck: Since this roof has a vaulted ceiling with condensation issues, it needs a vented deck, which means layering foam insulation and creating a small space for air to flow in the attic. This combo of breathing room and insulation protects the roof from condensation.

• Extended the eave through a valley by sistering rafters: We trimmed the beam and extended the eave all the way through the valley because the customer did not like the way it looked with a gap.

• Installed new skylight: Right next to the eave extension, the customer wanted a skylight installed. So the crew made sure to cut out a hole and put a curb in that spot to prepare for a curb-mounted skylight installation.
  

RoofSmart vs. Major Competitor: How did we prove that our roof solution was better even though it was more expensive?

Many customers think that our competitors offer the same thing we do for a lower price, but that’s just not true. We charge more because we’re doing more. Our commitment to solving all your roof issues and our ability to do things like framing and carpentry work make us stand out from other roofers. 

At RoofSmart, we know that our proposals are often more expensive than the proposals our competitors make. A lot of customers are hesitant to sign after seeing the cost, but once I make it clear that they are getting a lot of added value, they choose us.

For example, this customer got a proposal for $10k less than ours and was inclined to go with them because he thought that we would do the same thing. I requested that he send me the proposal so that we could compare and see if that was true.

Here are the big differences I found when comparing the other roofer’s scope of work to ours:

• The competitor offered:
• 26-gauge metal
• Installing roof on top of polyiso foam insulation (with no backer board)
• RoofSmart offered:
• 24-guage metal
• Vented deck with polyiso foam layers
• Will install metal roof on solid board (not foam)

I was alarmed to find out that the other roofing company was going to install the metal panels directly on top of the foam insulation because that is not how you fasten a metal roof to the roof decking. Foam can tear or break easily and does not hold screws securely. Metal needs to be installed on top of plywood, or another solid sheathing option.

This improper installation cut down the cost of the job by a lot. Also, they wanted to use a lighter, thinner metal size than I suggested, which is another thing that brought down the total cost.

My intervention secured the contract by demonstrating the value of RoofSmart's thorough scope of work. The customer could tell the difference in the thought that I had put into creating solutions for his roof’s problems. In the end, he was very happy with the way that the roof turned out.

Proper Vented Deck Installation Under a Standing Seam Metal Roof

How do you properly vent a vaulted ceiling under a metal roof?

This project shows that installing a standing seam metal roof is about much more than choosing a premium roofing material. To get the longevity and performance homeowners expect, the roof underneath has to be designed correctly.

In this case, solving the condensation problem meant creating a vented roof assembly, reinforcing the framing, installing solid roof decking, and addressing several other hidden issues before the metal panels ever went on.

It also highlights why comparing roofing proposals isn't just about price. A lower bid may leave out critical components like proper ventilation or solid sheathing, which are both details that can affect the lifespan of your roof.

Read our article “What Are the Challenges of Venting a Vaulted Ceiling in Seattle?” to learn why vaulted ceilings are especially vulnerable to condensation in Seattle's climate, the common ventilation mistakes roofers make, and the best solutions for keeping your roof dry, energy efficient, and built to last.