Professional Flat Roof Construction with Lantern Services

Look, I've been doing flat roof construction with lantern installations in Queens for over 20 years now, and let me tell you - this isn't something you want to mess around with. A lantern roof is essentially a raised glass structure that sits on top of your flat roof, bringing natural light into the space below while maintaining the clean lines of modern architecture.

The thing about building a flat roof with lantern is that it requires serious precision. You're not just laying down EPDM rubber or TPO membrane and calling it a day. We're talking about creating a proper structural opening, installing a curb system, ensuring perfect waterproofing around the lantern base, and making sure the whole thing can handle Queens weather - from those brutal summer storms rolling in from Jamaica Bay to the ice dams we get in February.

What Makes Flat Roof Construction with Lantern Different

Here's where most contractors screw up - they think a lantern is just like installing a skylight. Wrong. The structural requirements are completely different because you're dealing with a multi-sided glazed structure that needs to shed water in all directions while sitting on what's essentially a flat surface.

When we do flat roof construction with lantern work, we start with the roof deck preparation. The opening needs to be framed properly - usually with doubled-up joists or steel reinforcement depending on the span. Then comes the critical part: the upstand or curb. This thing needs to be at least 150mm high to prevent water ingress, and in Queens with our heavy rains, I usually go higher.

The membrane work around a lantern is where you separate the professionals from the weekend warriors. We use a combination of liquid membrane and reinforcement fabric around the perimeter, then tie it into the main roof membrane system. I can't tell you how many times I've been called to fix leaks where someone just slapped some sealant around the base and hoped for the best.

Structural Considerations for Queens Properties

Most of the buildings I work on in Astoria and Long Island City are older brick structures with flat roofs that weren't originally designed for lanterns. Before we even think about cutting into the roof deck, we need to assess the load-bearing capacity.

A typical lantern roof weighs anywhere from 200 to 400 pounds depending on size and glazing type. Plus you've got to factor in snow loads - the city requires us to design for 30 psf minimum, but with climate change, we've been seeing some crazy accumulations.

Last month we did a job on 31st Avenue where the homeowner wanted a massive 8x10 foot lantern. The existing joists were 2x8s on 16-inch centers - nowhere near adequate. We ended up installing a steel frame system that distributed the load to the exterior walls. Cost an extra $3,200, but that's what proper engineering requires.

Waterproofing Details That Actually Work

The devil's in the details with lantern installations. The upstand needs to be constructed with a positive slope away from the glass to prevent water pooling. We typically use a 1/4 inch per foot slope minimum.

For the membrane system, I prefer modified bitumen with a granulated cap sheet for the main roof area, then switch to liquid-applied membrane around the lantern perimeter. The liquid stuff - we use Tremco or GAF depending on the project - gives us the flexibility to create seamless connections around all those corners and angles.

• Primary seal at the glass-to-frame interface
• Secondary weatherseal on the exterior
• Structural gasket system for wind loads
• Drainage channels integrated into the frame
• Thermal breaks to prevent condensation

The drainage is crucial. Water needs a clear path off the lantern and away from the building. We usually install a perimeter drain around the upstand that connects to the main roof drainage system.

Glass Selection and Performance

Don't cheap out on the glazing. In Queens, we deal with temperature swings from below zero to over 90 degrees, plus the salt air if you're near the water. Standard double-glazed units just don't cut it.

I specify triple-glazed units with low-E coatings for most installations. The U-value should be 0.20 or better to meet energy code requirements. For safety, we use laminated glass on the exterior surface - when a tree branch comes down in a storm, you want the glass to crack but stay in place, not shower your living room with shards.

The glazing bars need to be thermally broken aluminum or composite. Steel looks nice but it'll condensate like crazy in our humid summers. We've had good luck with the Korniche system - British company but their engineering is solid for our climate.

Installation Process and Timeline

Building a flat roof with lantern typically takes us 3-5 days depending on complexity. Day one is structural work - cutting the opening, installing reinforcement, building the upstand. Days two and three are membrane and flashing installation. Day four is setting the lantern unit itself, and day five is final sealing and cleanup.

Weather's always a factor. We can't install the membrane if it's raining or if temperatures are below 45 degrees. Summer's the best time for this work, but everyone wants it done then, so schedule early.

The trickiest part is the crane work for larger units. Some of these lanterns weigh 800+ pounds and need to be set precisely. We usually bring in a small crane for anything over 6x6 feet. Street permits in Queens can take 2-3 weeks, so plan ahead.

Cost Factors and Realistic Budgets

Flat roof construction with lantern isn't cheap. For a basic 4x6 foot unit with proper installation, you're looking at $8,500 to $12,000. That includes structural modifications, membrane work, and a mid-range glazing unit.

Larger units or complex installations can run $15,000 to $25,000. I did one job in Forest Hills last year - custom 10x12 lantern with automated opening vents and integrated blinds - that came in at $28,000.

The breakdown typically looks like this:

• Lantern unit: 40-50% of total cost
• Structural work: 20-25%
• Membrane and flashing: 15-20%
• Installation labor: 15-20%

Don't forget about permits. The city requires a building permit for any structural opening over 2 square feet. That's another $500-800 depending on the value of work.

Common Problems and How to Avoid Them

I've fixed more botched lantern installations than I care to count. The most common issues are inadequate structural support, poor waterproofing details, and thermal bridging causing condensation.

Inadequate drainage is another big one. The lantern needs to be the high point of the roof section, with positive drainage away from the unit. I see contractors all the time who install the lantern in a low spot and then wonder why it leaks.

Thermal movement is something people don't think about. That aluminum frame is going to expand and contract with temperature changes. The membrane system needs to accommodate this movement without tearing. We use expansion joints and flexible sealants rated for the expected movement range.

Maintenance and Long-term Performance

A properly installed flat roof construction with lantern should give you 20+ years of trouble-free service. The glazing units typically come with 10-year warranties, but I've seen them last much longer.

Annual maintenance is pretty straightforward - clean the glass, check the drainage system, inspect the membrane around the perimeter for any cracking or separation. The gaskets might need replacement after 15-20 years depending on exposure.

Oh, and another thing about drainage - keep those gutters clean. A clogged drain can cause water to back up around the lantern base, and that's when you get problems.

The investment in quality materials and proper installation pays off in the long run. I've got customers with lanterns I installed 15 years ago that still look like new. Compare that to the cheap installations that start leaking after the first heavy rain.

If you're considering a lantern roof for your Queens property, get it done right the first time. The headache and expense of fixing a botched job isn't worth saving a few thousand upfront. At Flat Masters NY, we've perfected the process through hundreds of installations across Queens, and we stand behind our work with comprehensive warranties because we know it's built to last.