The Certification Process






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  • Accurate Ratings

    Local companies rated
    Highest in Quality and Helpful Expertise®

  • Performance Guaranteed

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  • Deep Info™

    Researched company reports.
    Essential articles and videos by topic experts.

Watch this video on the Diamond Certified Resource: the most accurate and trustworthy way to find local companies rated Highest in Quality and Helpful Expertise®. Companies must score 90+ on a 100 scale and pass all our credential-based ratings. By requiring such a high score to qualify, we cut out mediocre and poorly performing companies. Only the Best Pass the Test®.

We’ve all felt the joy of choosing a good local company and, unfortunately, the pain when we mistakenly choose a bad one. The problem is, every company claims to be good, yet despite these glowing claims some provide inconsistent quality while others are downright unscrupulous.

The Diamond Certified Difference

We’ve solved this problem for you with the Diamond Certified Resource. Only local companies independently rated Highest in Quality and Helpful Expertise® earn Diamond Certified. Our rigorous rating and certification process starts with the in-depth pass/fail rating of each company’s customer satisfaction, license and insurances. Most companies can’t pass our rating and earn Diamond Certified, and every Diamond Certified company must continue to deliver on its promises to you, the consumer. That’s why we conduct ongoing customer satisfaction research and credential-based ratings and monitor each company’s performance.

We’re Here for You

Every Diamond Certified company is backed by our powerful Performance Guarantee, so you’ll feel confident in your choice when you use our always-free web resource or Diamond Certified Directory. If you try unsuccessfully to resolve a disagreement with a Diamond Certified company, our mediator will work with you and the company to attempt to reach an agreement that both parties can live with. If the mediation fails to produce a mutually agreeable solution due to failure of the Diamond Certified company to honor contractual obligations, uphold industry standards or participate in good faith, we will refund your purchase price up to $1,000.

Each time you visit, you’ll see each Diamond Certified company’s Deep Info, including researched company rating reports, verbatim survey responses, essential articles, photo galleries, videos and expert tips. We put all the information you need to choose a company in one place, and no other web page can match this depth of information.

Only the Best Pass the Test®

When you choose a Diamond Certified company, you’ll never be fooled by fake or cherry-picked reviews because we survey a large, random sample of each company’s customers by telephone (typically 100 surveys) to get the most accurate ratings and verify only real customers are responding. Company owners can’t cherry-pick by telling friends and selected customers to post 5-star reviews on our site—we don’t allow it.

So, if you want quality, you’ll have confidence in choosing a Diamond Certified company. We encourage you to visit this website on a regular basis to find updated ratings on top rated companies in your area, see verbatim survey responses on each Diamond Certified company, and read thousands of industry-specific expert articles and tips. We care about customer satisfaction, and we care about you. We’re proud to give you all the information you need to choose with confidence.



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Each Diamond Certified Company Report gives you the most accurate and comprehensive Deep Info available for each company. It includes proof of Diamond Certified status, rating charts, verbatim survey responses, essential articles about the company, a capabilities table, a Diamond Certified Video Profile, key photos, company owner expert tip contributions and more. Click on the graphic to learn more


    We survey a large, random sample of each company’s customers by telephone to get the most accurate ratings...


    In addition to providing rating scores for Quality, Intent to Return and Helpful Expertise®, each surveyed customer is...


    You get to see the company in action, meet the managers, and learn as they describe their specialties and customer...


    You can choose to scan or go deep into these five researched articles on each Diamond Certified company: Company...


    Each company’s key info is logically organized within this table. You’ll find this system of display gives...


    Top rated local company owners are experts in their fields, and they’ve written topic-based expert articles and created...


    If a picture is worth a thousand words, how about an entire portfolio? You’ll get a better sense of each company once...


    This is a good place to go if you want to do extra research on a company. Here you’ll find a link to each company’s...

Creating a Heat-Resistant Home in the Bay Area

Posted on August 04, 2020 by James Florence

Here in the Greater San Francisco Bay Area, we don’t often suffer the extreme weather conditions experienced elsewhere in the United States. However, we do see our share of hot and cold weather, and unlike the rest of the country, our homes typically aren’t built to ward off either. Few homes in the Bay Area have central air conditioning, so when hot weather strikes, there isn’t much we can do but sweat it out.

One reliable way to beat the heat is to invest in home improvement measures that lower heat gain and increase energy efficiency. Some measures are more costly and intensive than others, but all of them can make your home more comfortable during hot weather.  Read more

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Posted in: Energy Efficiency, Seasonal, Bay Area, Home Improvement
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Diamond Certified TV Commercial Wins a 2020 Telly Award!

Posted on July 27, 2020 by Matt Solis

We’re excited to announce that Diamond Certified recently won a Telly Award for “Best Local TV Commercial.” Our CEO, Greg Louie, spearheaded the creation of three compelling Diamond Certified TV spots, which you can view below. Greg worked with the talented folks at Mnemonic Agency to create these effective commercials last year, which have since run thousands of times on 22 cable networks, KTVU and YouTube.

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Posted in: Press Releases, Uncategorized, Diamond Certified News
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  • Linda G.

    Verified customer
    Quality 10
    Loyalty Yes
    Helpful expertise Yes

    I have been very happy with the service for many years.
    When I had a really rundown old car, he didn't take advantage of me and helped me keep it running without extra costs. He was very fair.

    Response to Diamond Certified Company Gabe's Auto Care Center

  • Philippa H.

    Verified customer
    Quality 10
    Loyalty Yes
    Helpful expertise Yes

    They were here on time, very professional, and they were quick and clean.
    Probably just the professionalism

    Response to Diamond Certified Company JC Carpet & Upholstery Cleaning


John Alden is managing member of Mountain House Estate, a Diamond Certified company. He can be reached at (707) 948-6943 or by email.


John Alden: An Inspired Estate

By James Florence, Diamond Certified Resource Reporter

CLOVERDALE — Between his past livelihoods as an agricultural engineer and a real estate broker, John Alden has a pretty impressive professional resumé. However, one credential he never imagined he’d add is owner-operator of a wedding venue. “Not in a million years did I expect to be doing this,” he laughs. “It was sort of a coincidence, really. After living in Carmel for several years, I decided to move north of the Bay Area to be closer to my family’s timber and vineyard properties.

There was a property I’d driven by many times—over the years, I watched it be developed and go into foreclosure. Read more

Expert tip
Choosing a Focus for Your Wedding
CLOVERDALE — Every couple wishes they had an unlimited wedding budget, but unfortunately, very few have that luxury. Still, many couples operate as if they were on an unlimited budget and spread themselves too thin in the process.… Read more

Tommy Ngai is owner of Exclusive Auto Care and Auto Body, a Diamond Certified company. He can be reached at (650) 273-5409 or by email.


Tommy Ngai: Exclusive Expertise 

By James Florence, Diamond Certified Resource Reporter

REDWOOD CITY — Few automotive professionals can boast equal expertise in mechanical and body work, but that’s precisely Tommy Ngai’s claim to fame. It all began with an early introduction to the field. “I’ve been working on cars since I was 12 or 13 years old,” he recounts. “Growing up on a farm, my first encounters with auto repair work consisted of fixing tractors. My brother-in-law owned a gas station that had a little repair shop, and I went to work for him as soon as I was old enough.”

During subsequent years, Tommy worked at Honda and Subaru dealerships before opening his own repair shop in 2012. Read more

Expert tip
The Importance of a Pre-Purchase Auto Body Inspection
REDWOOD CITY — You probably know that before buying a used vehicle, you should take it to a professional mechanic to have it checked out. However, an additional step you might not be aware of is having your… Read more

Scott Yeaman is president of Yeaman Auto Body Inc., a Diamond Certified company. He can be reached at (408) 412-9572 or by email.


Scott Yeaman: An Educator at Heart

By James Florence, Diamond Certified Resource Reporter

PALO ALTO — Soon after he started doing auto body work to supplement his day job, Scott Yeaman realized he could make a better living if he made it his main career. “I used to be a math and science teacher in Palo Alto and Los Gatos,” he recounts. “I’ve always enjoyed working on and driving cars—I restored my ’55 Chevy and raced Porsches. My uncle had an auto body shop in Oakland and offered to give me some work to help me make ends meet. After training with him, I started doing auto body jobs on the weekends and during winter and summer breaks. Read more

Expert tip
2 Beneficial Additions to Your Auto Insurance Policy
PALO ALTO — When buying auto insurance, it’s important to know what you’re getting. Many people have a limited understanding of what’s included in their policies, and as a result, they may miss out on some beneficial perks.… Read more

Pat Martinez is owner of West Coast Mechanical, a Diamond Certified company. He can be reached at (831) 241-5070 or by email.


Pat Martinez: Service-Oriented

By James Florence, Diamond Certified Resource Reporter

LIVERMORE — After years working on the outskirts of the HVAC industry, Pat Martinez decided to venture further in, not realizing just how far those first few steps would eventually take him. “I used to work as a warehouse manager for a supplier of HVAC air filters,” he recounts. “At a certain point, I was feeling tired of managing people and wanted to do something a little more hands-on. I saw these HVAC technicians coming into the warehouse every day and I figured, ‘Why not try that?’ I ended up getting into the union and becoming an apprentice. The funny thing is, Read more

Expert tip
Understanding HVAC Maintenance
LIVERMORE — You’ve probably heard that HVAC maintenance is important, but you may not know why it’s important or what exactly it consists of. To provide further insight, here’s some basic information on HVAC maintenance. Why is HVAC… Read more

Luiz Cardoso is owner of Select Pavers, Inc., a Diamond Certified company. He can be reached at (408) 713-1094 or by email.


Luiz Cardoso: A Select Opportunity

By James Florence, Diamond Certified Resource Reporter

HAYWARD — A career setback can be disheartening, but Luiz Cardoso isn’t the type to lose heart easily. Even after being laid off from his long-time position, he kept his head up, and as a result, he was able to spot an even bigger opportunity. “I used to be a manager for Comcast, where I supervised more than 80 employees,” he recounts. “In 2012, the company started downsizing its managers and I was let go. It was a sad day, but with the experience and training I had under my belt, I knew I wouldn’t be out of work for long.”

Unable to find another managerial job that paid as well, Read more

Expert tip
An Important Factor for Paver Selection
HAYWARD — When choosing pavers for a home project, it’s important to consider the scope of your options. There are a lot of characteristics to look for in a paver, including color and material type. However, an additional… Read more

Forest Kirk is president of Forest Tree Services Inc., a Diamond Certified company. He can be reached at (707) 927-1019 or by email.


Forest Kirk: Professional Growth

By James Florence, Diamond Certified Resource Reporter

SANTA ROSA — Thanks to an early introduction to the tree service industry, Forest Kirk was able to achieve uncommonly rapid professional growth. “When I was growing up, my mom’s boyfriend owned a tree service business,” he explains. “When I was 11 years old, I started working with him after school and during the summer. I’d also go with him to Fort Ross, where we’d clear out forested areas and process the timber into firewood. Following high school, I started working for another tree service company and trained with a certified arborist. A couple of years later, I decided to start my own tree service business. Read more

Expert tip
Annual Tree Maintenance
SANTA ROSA — Maintaining your trees once a year will ensure their long-term health, make your property safer and save you money. Almost all trees require a similar annual maintenance regimen. This includes: •  Trimming back excess growth… Read more

Paul Gerrard is president of Big Blue Plumbing, a Diamond Certified company. He can be reached at (510) 962-6113 or by email.


Paul Gerrard: Pursuing Excellence

By James Florence, Diamond Certified Resource Reporter

ALAMEDA — Originally from England, Paul Gerrard may have come to the United States in pursuit of adventure, but he stayed to pursue excellence in his trade. “My father was a plumbing and heating contractor, and I apprenticed with his company when I was a young man,” he recounts. “Having an itch for adventure and excitement, I left England in 1996 and came to the States. I found that plumbing in the U.S. was very different from what I was used to, so I basically had to relearn my trade.”

However, the nuts and bolts of the job weren’t the only differences Paul noticed between the plumbing industries in England and the U.S. Read more

Expert tip
Technologically Advanced Water Heater Options
ALAMEDA — Question: Which of the plumbing appliances that you use every day has had no technological advancement in more than 100 years? Answer: your water heater. The traditional storage tank water heater was designed and patented in… Read more

Angel Garcia is owner of Gar-Cal Corporation, a Diamond Certified company. He can be reached at (510) 346-5017 or by email.


Angel Garcia: Expanded Expertise

By James Florence, Diamond Certified Resource Reporter

LIVERMORE — Starting out in a subset of the remodeling industry, Angel Garcia gradually expanded his expertise to encompass all aspects of construction. “Several of my family members were in construction, so I basically followed in their footsteps,” he recounts. “My first job was installing garage doors when I was 18 years old. Later, I started doing handyman services, which I enjoyed so much that I decided to get my general contractor’s license. In 2011, I started Gar-Cal Corporation, and today we handle every aspect of construction, from foundations to framing to whole home remodeling.”

Angel says his favorite part of his job is the opportunity for creative ingenuity. Read more

Expert tip
The Importance of Project Preparation
LIVERMORE — No matter what kind of home improvement project you’re planning, chances are you’ll need to invest some time and money into preparation. Doing so will allow you to get the best possible result with your project.… Read more

Billy Alcantara is owner of Safeshield Construction Inc., a Diamond Certified company. He can be reached at (925) 276-5607 or by email.


Billy Alcantara: An Unexpected Opportunity

By James Florence, Diamond Certified Resource Reporter

BENICIA — Following a hiatus from the construction industry, Billy Alcantara found himself drawn back into the field by an unexpected opportunity. “I’ve always been a hands-on type of person, so right out of high school I put on a toolbelt and got into construction,” he remembers. “My older cousin got me into the trade and showed me the ropes. A few years later, I left the construction field to work in sales, and after that I took a job in the manufacturing field. After the financial crash in 2008, my wife and I began to invest in and fix up real estate properties. Read more

Expert tip
Choosing Siding for a Hillside Property
BENICIA — If you’re planning to replace the siding on your home, you have a lot of options to choose from. For example, fiber cement siding has become very popular due to its fire-, water- and termite-resistant characteristics.… Read more

Niv Goldman is owner of Alley Cat, a Diamond Certified company. He can be reached at (415) 523-6064 or by email.


OAKLAND — After a bad experience as an employee, Niv Goldman decided the best way to maintain his professional ethics was to take matters into his own hands. “While working as a salesperson for a large attic cleaning company, I kept getting complaints from unhappy clients,” he recounts. “I tried to work with the company owner to rectify the issue—I didn’t feel right setting expectations higher than what I knew we could provide. Eventually, I knew I had to move on. Instead of going to work for another company and ending up in the same situation, I decided to get my contractor’s license and start my own attic cleaning business.”

Knowing he’d need help getting his new business off the ground, Read more

Expert tip
Identifying and Treating a Rodent Infestation
OAKLAND — It’s not always easy to know when rodents have infested your home—after all, they’re quite good at hiding. Fortunately, even if you can’t see them, there are plenty of clues that can alert you to their… Read more

Chris Marcus is CFO of Miracle Plumbing Inc., a Diamond Certified company. He can be reached at (408) 620-4975 or by email.


Chris Marcus: Like Father, Like Son

By James Florence, Diamond Certified Resource Reporter

SAN JOSE — Having been raised by a plumber, it’s no surprise that Chris Marcus grew up to become one himself. “My father, Phil, has been a plumber since before I was born,” he recounts. “I started going to work with him when I was eight or nine years old. As time went by, I started doing bigger and more complex projects, and by the time I was 16, I had pretty much decided I was going to do plumbing as a career. After doing my own thing for several years, I ended up going into business with my father, Read more

Expert tip
Making Water Heater Maintenance Financially Viable
SAN JOSE — Regardless of what type of water heater you have, if you want it to achieve its full lifespan, you’ll need to maintain it consistently. A traditional water heater needs to be flushed annually to remove… Read more

Gabriel Martinez is owner of Supreme Comfort HVAC, Inc., a Diamond Certified company. He can be reached at (831) 217-3172 or by email.


Gabriel Martinez: One Step Toward Success

By James Florence, Diamond Certified Resource Reporter

MORGAN HILL — When Gabriel Martinez took a job in the HVAC industry at age 18, he had no idea just how far that initial step would eventually lead. “My first job after high school was working in a warehouse for a heating and air conditioning distributor,” he recounts. “A few years later, I got into the field doing maintenance and installation for a couple of contractors. I liked being out in the field—the day goes by much faster when you aren’t stuck in the same place. About four years later, in 2006, I decided to go into business for myself. Read more

Expert tip
The Importance of Changing Your HVAC Air Filter
MORGAN HILL — A crucial aspect of maintaining your heating, ventilation and air conditioning (HVAC) system is regularly replacing its air filter. The purpose of an HVAC air filter is to catch dust, dirt, pet dander, smoke particles… Read more