Every input explained, the common mistakes flagged, and the ASCE 7 engineering methodology behind the numbers — for installers who need the answer fast and engineers who need to understand the math.
The same mount, the same antenna, the same height — but two very different ballast requirements depending on where you're standing.
Consider two identical installations: a 1.2m satellite dish on a Baird B4-4x4 at 3' mast height. One is on a 2-story suburban office building in Cedar Falls, Iowa. The other is on a 10-story coastal commercial building in Miami Beach. The Miami installation requires roughly 3–4 times more ballast than the Cedar Falls installation — not because the mounts are different, but because wind speed, building height, and exposure category compound dramatically.
This is why "fill the trays" is genuinely good advice for low-exposure sites and genuinely dangerous advice for high-exposure ones. And it's why running the calculation works in both directions — on many sheltered residential or suburban commercial installs, you may only need a portion of the tray capacity. That's real time saved on the roof, less weight to haul, and lower PSF loading on the roof structure.
Under-ballasting risks catastrophic mount failure in high winds — equipment damage, roof damage, and liability exposure. Over-ballasting wastes crew time, adds unnecessary roof loading, and on PSF-sensitive roofs can itself be a problem. Site-specific calculation is the only way to know which situation you're in.
The good news: the inputs are straightforward, Baird's ballastcalc.com does all the math, and the output is a printable document your customer, building engineer, or permit authority can review. The whole process takes under five minutes once you understand what each input means — which is exactly what this guide covers.
Every ballast calculation traces back to six variables. Understanding each one is the difference between a number you trust and a number you're guessing at.
The first question ballastcalc.com asks is what you're mounting. The dropdown contains hundreds of pre-loaded equipment configurations — antennas, cameras, Starlink models, satellite dishes, and wireless gear — each with a specific make, model, and mounting height already built in. Select your device and the tool automatically handles the wind area calculation for you. You don't need to look up EPA values or do any math — just find your equipment in the list.
Start typing your city name and the tool presents a matching list — select your city and ballastcalc.com automatically retrieves the correct ASCE 7-10 design wind speed for that location from the ASCE wind speed map. You never need to look up wind speed manually. In the continental U.S., design wind speeds range from roughly 85 mph in the sheltered midwest interior to 160+ mph along the Gulf Coast and Florida peninsula.
Wind speed increases with height above the ground. ASCE 7 models this through the velocity pressure exposure coefficient (Kz), which increases as height increases. The formula follows a power law — roughly, wind pressure at 200 ft is about 40–60% higher than at 30 ft, depending on exposure category. Enter the height of the roofline where the mount will sit, measured from the ground.
Select your roof surface material from the dropdown. Each roof type has a friction coefficient that Baird determined through internal testing — the calculator applies the correct value automatically based on your selection, so you don't need to know the numbers. The tool also asks separately whether the roof is peaked (Yes/No), which determines whether a flat-base NPRM or a peak ridge mount is appropriate for your installation.
This field lets you manually enter a wind speed if you have site-specific data or a value from a licensed engineer that differs from the automated city-based value. For most installations, leave this blank — the city selection in Step 2 already retrieved the correct ASCE 7-10 design wind speed for your location. Only use this field if you have a specific reason to override the automated value.
Exposure category describes the roughness of the terrain surrounding your site for a half-mile or more in the upwind direction. It is the single most consequential input in the calculation — the difference between Exposure B and Exposure D can change your required ballast weight by 50–80% on the same building at the same location.
If you're mounting solar panels, equipment enclosures, or other hardware on the mast alongside the antenna, select each additional item from the equipment dropdown as well. Mount additional items as low on the mast as possible — the overturning moment increases with height, so a solar panel at 8' contributes far more to the required ballast than the same panel at 2'.
The practical sequence for getting from a site address to a printable ballast document.
Navigate to ballastcalc.com. The tool is free, requires no account, and runs entirely in the browser. Here's the sequence:
After getting your ballast weight, verify that the resulting PSF (pounds per square foot) load is within your roof's rated capacity. The ballastcalc.com output includes this number. If PSF exceeds your roof's rating, do not simply reduce ballast — instead, step up to a larger-footprint mount base (B4-4x4 or B4-6x6) that spreads the same weight over more area. See the NPRM selection guide for PSF guidance by mount model.
The calculator produces two separate ballast requirements. Here's what each means and which one governs your installation.
The weight needed to prevent the mount from tipping over — rotating about its leeward base edge under wind load. This is the more commonly governing value. It increases with mast height, antenna EPA, and building height. The moment arm (mast height + half the mount base height) amplifies the wind force significantly at taller mast heights.
Always use the larger of the two values. The ballastcalc.com output will indicate which one governs for your specific inputs. If the required ballast weight exceeds the capacity of your selected mount's tray configuration, the solution is not to under-fill — it is to move to a mount with more tray capacity or a larger base footprint.
The output gives both a weight (lbs) and a recommended block count. Standard concrete ballast blocks used with Baird mounts weigh approximately 35–40 lbs each. The block count is calculated based on the specific blocks compatible with your mount's tray dimensions. When sourcing blocks locally, verify the weight per block matches the assumed value — lighter decorative pavers are not a substitute for dense concrete ballast blocks.
Most installation problems trace back to one of these. All of them are easy to avoid once you know they exist.
A 1.8m dish is not 1.8 × 1.8 meters of wind area. The EPA accounts for the parabolic shape's actual aerodynamic load and typically runs 3–5× higher than the geometric area. Always use the antenna manufacturer's EPA value from the spec sheet.
Rooftops of high-rise buildings, sites near coastlines, and open-terrain commercial properties frequently qualify as Exposure C or D. The terrain upwind of the site — not just what's immediately surrounding the building — determines the correct category.
Building height is the distance from the ground to the roof surface. Mount height is the additional mast height above that. They are entered separately. Confusing them — entering, say, 15 ft when the building is 40 ft tall — dramatically under-calculates the required ballast.
A solar panel, equipment enclosure, or even a large cable bundle on the mast adds wind area. These items are often omitted from the EPA input. Estimate the frontal area of every item on the mast and add it to the antenna EPA before running the calculation.
Concrete paving stones and decorative garden blocks are typically 20–30% lighter per unit volume than dense ballast-grade concrete blocks. If your calculation assumes 38 lb blocks and you use 28 lb pavers, you are under-ballasted even with a full tray. Source ballast blocks that match the weight assumed in the documentation.
Getting the right ballast weight is only half the job. If that weight loaded into a small-footprint mount exceeds your roof's PSF rating, you have a structural problem even if the mount won't blow over. Always verify PSF against the building's structural documentation or the building engineer's guidance.
If the antenna changes, a solar panel gets added, or the mount gets moved to a different part of the roof (different height, different exposure), the calculation needs to be re-run. The original documentation is specific to the exact inputs entered — it does not cover modifications.
For structural engineers, system designers, and anyone who wants to understand what the calculator is actually computing.
Ballastcalc.com implements ASCE 7-10 Chapter 27 and 29 wind load methodology for components and cladding, adapted for non-penetrating roof mount stability analysis. The calculation has two independent checks — overturning and sliding — and the governing (larger) ballast weight is the required minimum.
The velocity pressure at height z is calculated as:
Kz varies with height and exposure category per ASCE 7-10 Table 27.3-1. Representative values:
| Height (ft) | Exposure B | Exposure C | Exposure D |
|---|---|---|---|
| 15 | 0.57 | 0.85 | 1.03 |
| 20 | 0.62 | 0.90 | 1.08 |
| 30 | 0.70 | 0.98 | 1.15 |
| 40 | 0.76 | 1.04 | 1.22 |
| 60 | 0.85 | 1.13 | 1.31 |
| 80 | 0.93 | 1.21 | 1.38 |
| 100 | 0.99 | 1.26 | 1.43 |
| 150 | 1.12 | 1.36 | 1.52 |
| 200 | 1.20 | 1.43 | 1.59 |
This table illustrates why exposure category matters so much: at 30 ft, the Kz for Exposure D is 64% higher than for Exposure B — meaning the wind pressure is 64% higher before any other factors are applied.
The overturning moment MOT is the wind force multiplied by its moment arm (the height from the base pivot point to the centroid of the wind force). The resisting moment MR must equal or exceed MOT with the required safety factor.
The governing required ballast is max(Woverturn, Wslide). Ballastcalc.com computes both and reports them separately so you can see which one controls your installation.
The ballastcalc.com output provides an ASCE 7-10 based calculation suitable for presentation to building owners, facilities managers, and most commercial sites. It does not constitute a stamped engineering document. For projects requiring a licensed PE stamp — certain permit jurisdictions, government facilities, or high-value commercial projects — use the ballastcalc.com output as the basis document and submit it to a licensed structural engineer for review and stamp.
A real-world commercial installation, calculated step by step.
A systems integrator is installing a Starlink Flat High Performance antenna at 5' mast height on the roof of a commercial building in Houston, Texas, 75 feet above grade. The building is in a mixed commercial area — mostly flat, open terrain on three sides. They run the inputs through ballastcalc.com to get the mount recommendation, required ballast, and a printable documentation package.
Results from an actual ballastcalc.com calculation. Run your own site inputs at ballastcalc.com for site-specific results and printable documentation.
Notice this result: the calculator recommended the B4-6x6 rather than a smaller mount — the B4-6x6's larger 72"×72" footprint keeps PSF at a manageable 10.2 even with the full ballast load. The same antenna at 5' on a 2-story suburban building in Exposure B in Cedar Falls, Iowa would require significantly less ballast, demonstrating how much exposure category and building height drive the final number.
There is no single answer — ballast requirements depend on six site-specific factors: geographic location, ASCE 7 exposure category, building height, mount height, antenna EPA, and roof surface type. For a small antenna at low height on a suburban building, you may need 100–200 lbs. For a large antenna at tall height on a coastal high-rise, you may need 800 lbs or more. Use ballastcalc.com for a site-specific number.
Overturning ballast resists the wind trying to tip the mount over, rotating it about its leeward base edge. Sliding ballast resists the wind trying to push the mount horizontally across the roof. Both are calculated separately. The larger value governs. On most commercial installations overturning controls, but on very low masts or high-friction surfaces sliding can occasionally govern.
EPA (Effective Projected Area) is the wind-catching surface area of your antenna in square feet, accounting for the dish shape. It is found in the antenna manufacturer's technical datasheet or installation manual — not calculated from the physical dish diameter. For Starlink Flat High Performance, EPA is approximately 4.8–5.2 sq ft. For a 1.2m satellite dish, approximately 7–10 sq ft depending on manufacturer.
The calculation works in both directions. On sheltered sites at low building heights with small antennas, full trays are usually more than sufficient — and the calculation will confirm that quickly, potentially saving you significant hauling time. On high-exposure sites, full trays may not be enough. The five minutes it takes to run the calc removes all guesswork in both directions and gives you a document you can share with the building owner.
Ballastcalc.com uses ASCE 7-10 methodology, which remains the most widely referenced standard for non-penetrating mount ballast calculations and is accepted by building engineers and permit authorities across North America.
Do not under-ballast. Instead, step up to a mount with more tray capacity or a larger base footprint. The Baird B4-4x4 (48"×48" base) and B4-6x6 (72"×72" base) both accept the same mast pipe and adapters as the smaller Starlink NPRM, but provide more tray capacity and spread the load over more roof area — reducing PSF at the same time. See the NPRM selection guide for details.
The ballastcalc.com output is an ASCE 7-10 based engineering calculation document suitable for most commercial sites, building owners, and facilities managers. It does not carry a licensed PE stamp. For jurisdictions requiring a stamped document, use the ballastcalc.com output as the basis calculation and submit to a licensed structural engineer for review and stamp — this significantly reduces the engineer's time and your cost compared to a calculation from scratch.