Window Replacement in Myrtle Beach: What to Know First

Window replacement in Myrtle Beach succeeds or fails on three things: the ratings printed on the label, the way the window is installed and flashed into the wall, and whether the job meets the coastal requirements of the South Carolina Residential Code. Style and color matter to you, but wind pressure, wind-driven rain and windborne debris are what test a window on the Grand Strand.

Top GM Construction is a licensed and insured general contractor with more than 17 years of experience, offering window repair and replacement in Myrtle Beach, North Myrtle Beach, Conway, Surfside Beach, Murrells Inlet and Little River. This guide walks through what the code, FEMA and the rating programs actually say, in plain language, so you can compare products and hold any bid you receive (ours included) to the same standard.

Why coastal conditions change how windows are replaced

In Horry County, South Carolina, a replacement window is judged by how it handles wind, water and flying debris, not only by how well it insulates. The South Carolina Building Codes Council publishes a wind map for each county, and the Horry County map places the ocean side of the county in the highest wind-speed bands the residential code uses. That is why windborne debris protection (glass that resists, or is shielded from, objects carried by the wind) comes up on most coastal window jobs here. The map is a planning tool, not a ruling on your house: the local building official confirms what applies at a specific address.

Water is the load homeowners tend to underestimate. According to FEMA’s 2023 Hurricane Ian Recovery Advisory 3, whose recommendations "can be applied throughout the United States," water intrusion "can cause dry rot and fastener corrosion that weaken the window or door frame or the wall itself." A leak at a window rarely stays a window problem; it becomes a wall problem.

Salt air, humidity and heat are part of the picture too. They do not change which rating you need, but they are a good reason to ask each manufacturer for its written coastal guidance and to keep up with the maintenance described below.

Repair or replace: signs that point each way

Repair a window when the unit itself is sound and the problem is a wear item; replace it when the frame, the glass seal or the opening around it has failed. FEMA’s Hurricane Ian Recovery Advisory 3 treats several common issues as maintenance rather than failure: sealants "can degrade over time and will need to be replaced once they exhibit signs of edge curling, cracking, and/or other breaks or delamination," and "sealant joints require periodic inspection and replacement." The same advisory says weep holes (the small drain openings in the bottom of the frame) "should not be covered or plugged with caulk."

Full body of unrecognizable handyman on windowsill with instruments assembling window while working in room with battery during renovation works — Illustrative photo by Ksenia Chernaya on Pexels. Ksenia Chernaya / Pexels

Interior of room with wooden workbench and windows removed from hinges with white frame placed near wall in light room during repair works — Illustrative photo by Ksenia Chernaya on Pexels. Ksenia Chernaya / Pexels

Signs that lean toward repair:

Cracked or curling exterior sealant with no water stains or soft material behind it
Weep holes blocked by dirt, paint or caulk
A sash that sticks, or hardware and latches that no longer close firmly
A single cracked pane in an otherwise healthy unit

Signs that lean toward replacement:

Soft, swollen or rotted frame material, or rot in the sill or wall below the window
Water stains on interior trim or drywall after storms, even after the sealant was redone
Fog or condensation trapped between panes of an insulated glass unit
Windows that have no label or known ratings, in a location where the building official expects impact protection

When water has been getting past the unit for a while, the real question is what the opening looks like behind it. That usually cannot be answered until the old window comes out, which is why a careful bid explains how hidden damage will be handled.

Impact windows or shutters: what the code asks near the coast

Near the South Carolina coast, the residential code requires exterior glass in windborne debris regions to be protected, and either impact-rated windows or approved protection over standard windows can meet that requirement. Section R301.2.1.2 of the 2021 South Carolina Residential Code states: "Exterior glazing in buildings located in windborne debris regions shall be protected from windborne debris." The same section allows an exception using wood structural panels at least 7/16 inch thick, spanning no more than 8 feet, fastened according to its table.

A windborne debris region is the part of a hurricane-prone area where the code expects glass to be protected, defined by wind speed and distance from the water. As quoted in a South Carolina permitting guide from the City of Goose Creek, it covers "portions of hurricane-prone regions that are within 1 mile of the coastal mean high-water line where the basic wind speed is 130 mph (49 m/s) or greater," or portions of the hurricane-prone region "where the ultimate wind speed is equal to or greater than 140 mph (54 m/s)." Whether your property falls inside that definition is the building official’s call, based on the state map.

Impact protection is proven by testing, not by a sales description. According to the Building America Solution Center at Pacific Northwest National Laboratory, building codes require "impact-resistant glass, shutters, or panels for new homes located in ‘Windborne Debris Regions,'" with products "rated and labeled in accordance with ASTM E 1996 and ASTM E 1886 or AAMA 506." The City of Goose Creek guide adds: "Impact resistant glazing that meets ASTM E 1886 and 1996 is compliant and offers continuous protection without having to install panels or shutters," and information on the proposed compliance method "must be submitted for review at the time of application and approved by the Building Official prior to installation." That is Goose Creek’s policy, not Horry County’s, but it shows how a South Carolina building department can treat the question.

Two more points are worth knowing. According to the same Solution Center page, the FORTIFIED Home standard "requires that all windows, exterior doors, and skylights be impact rated or protected with qualified protection systems" for houses in hurricane zones, tested for large missile "D," and protected glazing "may help qualify for a homeowner’s insurance policy discount." Ask your insurer what documentation they need before you order windows, not after. The South Carolina Department of Insurance also runs the SC Safe Home program, which lists impact-rated or wind-rated windows among eligible improvements for primary residences in coastal counties designated by the program; when we checked in September 2026, the program page said it was not currently accepting applications.

Design pressure and performance grade: the two numbers that matter most

On a window label, design pressure (DP) is the wind load, in pounds per square foot (psf), the window is rated to resist, and performance grade (PG) is a rating tied to a minimum DP that also required passing a water penetration test. They are not the same thing. According to FEMA’s 2023 Hurricane Ian Recovery Advisory 3, "the DP rating is not always an indication of water penetration resistance. The important designation regarding water penetration resistance is the PG rating."

FEMA’s advisory gives a worked example: "A product with the PG rating of 60 has a minimum DP rating of 60 pounds per square foot (psf) and has passed the water penetration resistance test at 15% of the positive DP rating, 9 psf. The higher the PG rating, the more resistant the product is to water penetration." For products tested to AAMA/WDMA/CSA 101/I.S.2/A440, FEMA’s key recommendation is to "ensure all windows and sliding doors have a PG rating that equals the positive DP rating for the product."

You will find these numbers on the label. FEMA’s advisory shows a real temporary label that carries a design pressure block (for example "+38.7 / -60.0 psf"), the test standard, and an energy block from the National Fenestration Rating Council (NFRC), the organization whose certified ratings ENERGY STAR uses, listing U-factor, solar heat gain coefficient (SHGC), visible transmittance and air infiltration, along with the instruction "DO NOT REMOVE LABEL PRIOR TO INSPECTION." One sticker carries both the structural and the energy ratings, and inspectors look for it. The residential code’s window labeling section, R609.3, which follows the model International Residential Code text, requires exterior windows and sliding doors to be tested by an approved independent laboratory and to bear a label identifying the manufacturer, performance characteristics and approved inspection agency.

Window style affects water resistance too. FEMA’s advisory notes that "fixed windows and operable window and door products with compression seals provide the best resistance to water infiltration," naming awning and casement windows, and it groups double-hung and sliding windows under less effective water intrusion resistance. That does not rule out a double-hung window, but on an exposed wall it is a reason to look harder at the PG rating and the installation detail.

Window replacement permits in Myrtle Beach and Horry County

Plan on a permit to replace windows in Myrtle Beach or elsewhere in Horry County, because window replacement is not on the list of permit-exempt work in section R105.2 of the 2021 South Carolina Residential Code. Section R105.1 of that code says anyone who "intends to construct, enlarge, alter, repair, move, demolish or change the occupancy of a building or structure ... shall first make application to the building official and obtain the required permit." The R105.2 exemptions cover items like fences, sidewalks, painting and finish work, small decks and window awnings, not window replacement.

Horry County’s "When to get a Building Permit" page repeats the same requirement and the same kind of exemptions, including window awnings, and does not list window replacement as exempt. The City of Myrtle Beach answers the question this way: "The answer, generally, is ‘yes,’ but exceptions exist," and points residents to its Construction Services department. The city also states that contractors working inside city limits must hold a City of Myrtle Beach business license and be licensed by the South Carolina Department of Labor, Licensing and Regulation (SC LLR), the state agency that licenses builders.

Section R102.7.1 of the 2021 South Carolina Residential Code adds a principle that matters for replacement work: alterations and repairs "shall not cause an existing structure to become less compliant with the provisions of this code than the existing building or structure was prior to the addition, alteration or repair." Swapping a window for one that does less than the one you have is exactly the kind of change that sentence is written to prevent.

South Carolina currently enforces the 2021 South Carolina Residential Code, which took effect on January 1, 2023. A newer code cycle is in the adoption process, so confirm the edition in force with Horry County Code Enforcement or your city’s building department when you apply.

Full-frame or insert replacement: which one fits your house

Insert replacement fits a house whose existing window frames are sound and dry, and full-frame replacement fits a house with signs of leaks or rot, because only full-frame removal exposes the opening for repair. An insert (also called retrofit or pocket) replacement sets a new window inside or over the existing frame; a full-frame replacement removes the old window down to the rough opening, the framed hole in the wall. Each has its own industry installation standard, published through FGIA: AAMA 2410 "covers the installation of retrofit windows" and applies to retrofit windows "with an exterior flush fin installed over a pre-existing window frame," while FMA/AAMA/WDMA 2710 gives guidelines for full-frame replacement of windows without removing external brick veneer and notes that "many variations in existing conditions will be encountered."

Neither method is automatically right. Because an insert works within the existing frame, ask the installer to show you how the finished opening and glass area will compare with what you have now before you decide.

Installation is where windows fail: flashing, sill pans and anchoring

A window’s ratings only hold when it is installed exactly as its manufacturer specifies, so flashing, sill pans and anchoring decide whether a well-rated window stays dry. According to FEMA’s 2023 Hurricane Ian Recovery Advisory 3, "Installation of windows and doors is not generic and is specific to each manufacturer to achieve the required performance ratings such as the design wind DP rating and water penetration resistance," and "It is critical that windows and doors be installed as specified by the manufacturer."

Flashing laps like shingles

Flashing is the layered material around the opening that sheds water down and out. FEMA’s advisory states: "Flashing is required to be applied in shingle-like fashion, where the top layer laps over the bottom layer to direct water down and out of a structure. One of the more common window and door flashing mistakes is the failure to layer flashing in a shingle-like fashion." Section R703.4 of the 2021 South Carolina Residential Code says the same, requiring approved corrosion-resistant flashing "applied shingle-fashion in a manner to prevent entry of water into the wall cavity or penetration of water to the building structural framing components."

Windows and siding meet at exactly this detail. If your siding is also due, our guide to siding installation in Myrtle Beach explains the water-resistive barrier and flashing behind the cladding, the same layer the window flashing has to lap into.

A sill pan catches what gets past

A sill pan (pan flashing) is flashing installed at the bottom of the opening, where water collects. Section R703.4.1 of the 2021 South Carolina Residential Code states: "Where flashing instructions or details are not provided, pan flashing shall be installed at the sill of exterior window and door openings." The pan has to be "sealed or sloped in such a manner as to direct water to the surface of the exterior wall finish or to the water-resistive barrier for subsequent drainage." FEMA’s Home Builder’s Guide to Coastal Construction (FEMA P-499) has a technical fact sheet on window and door installation, which the Building America Solution Center describes as covering "flashing detail concepts for window and door openings that provide adequate resistance to water intrusion in coastal environments."

Anchoring holds the whole system together

Fastener type, spacing and embedment come from the product’s approval and installation instructions, not from habit. FEMA’s advisory explains why that matters for water, not only for wind: "If the window and door assemblies are not anchored properly as specified by the Product Approval, flashings and sealants may be less effective during a windstorm, resulting in water intrusion." After installation, the maintenance items from the repair section still apply: periodic sealant inspection and replacement, and open weep holes.

Energy ratings on the label: U-factor, SHGC and ENERGY STAR

For a home in Myrtle Beach or elsewhere in Horry County, the two energy numbers to compare on a window label are U-factor (how much heat moves through the whole window; lower is better) and solar heat gain coefficient, or SHGC (how much of the sun’s heat comes through; both the state energy code and ENERGY STAR cap it for this climate). Both appear in the National Fenestration Rating Council (NFRC) block on the label, and ENERGY STAR bases its window criteria on "ratings certified by the National Fenestration Rating Council."

Horry County is climate zone 3A in the South Carolina Energy Code (the 2009 International Energy Conservation Code, adopted by state law) and is marked as a warm-humid county. For zone 3, the energy code’s table lists a maximum fenestration U-factor of 0.50 and a maximum SHGC of 0.30, with a footnote allowing a maximum U-factor of 0.65 in zone 3 for impact-rated fenestration. Whether those values apply to your particular replacement job is a question for the permit office, but they are a useful baseline when comparing products.

ENERGY STAR sets tighter targets that vary by its own climate zones, which are not the same map as the code’s. Under the Version 7.0 criteria (the version ENERGY STAR listed as of September 2026), the South-Central zone calls for a U-factor of 0.28 or lower and an SHGC of 0.23 or lower; the Southern zone calls for a U-factor of 0.32 or lower and an SHGC of 0.23 or lower; and air leakage must be 0.3 cfm per square foot or lower. Check the ENERGY STAR climate-zone map for your ZIP code to see which set applies to your home.

Choosing a frame material for a coastal home

The most reliable way to choose a frame material for a coastal home in Myrtle Beach is to compare the window labels and each manufacturer’s written coastal guidance, not a material ranking. Vinyl, fiberglass, aluminum, wood and composite frames are all sold for coastal homes. This guide does not rank them for salt-air durability, because we have not found a primary source that does so.

Put the labels side by side: the NFRC block tells you how the whole unit performs on energy, and the DP, PG and impact information tells you how it performs on wind and water. Then ask each manufacturer for its written guidance on coastal or salt exposure, including any maintenance it expects, and read how that guidance connects to the product warranty.

How to read a window replacement bid: ten items to check

A window replacement bid in Myrtle Beach should answer the ten items below in writing before you sign. Use the same list on each bid you collect.

The product by name and series, with the label ratings: DP (positive and negative), PG, and the NFRC U-factor and SHGC.
Impact protection method. Impact-rated glazing tested to ASTM E1886 and E1996, or the approved protection system that will be used instead, and confirmation that the building official accepts it for your address.
PG compared to DP. FEMA recommends a PG rating equal to the positive DP rating. Ask whether each unit meets that.
Installation method, named. Insert or full-frame for each opening, and whether the installation follows the manufacturer’s instructions and, where one applies, the matching industry standard (for example AAMA 2410 for a flush-fin retrofit over an existing frame, or FMA/AAMA/WDMA 2710 for full-frame replacement in a brick veneer wall).
Flashing and sill pan. How the opening will be flashed shingle-fashion and how the sill will drain, plus how anchoring will follow the product approval.
Permit and inspection. Who applies for the permit, who arranges the inspection, and a note that labels stay on the windows until the inspection is done.
Safety glazing. Some locations, such as large low panes near walkways, glass next to doors, and glass in bathrooms and near stairs, require safety glazing under the residential code. The bid should flag which openings need it.
Bedroom egress. Bedroom windows are also emergency escape openings. Ask how the replacement keeps or improves the opening size in each bedroom.
Lead-safe work for older homes. If your house was built before 1978, the EPA’s Renovation, Repair and Painting (RRP) rule, which sets lead-safe work practices for contractors, applies, and the EPA notes that "window replacement and demolition of painted surfaces are always covered regardless of square footage." Ask how the crew will meet it.
License and scope. Verify the contractor on the SC LLR license lookup, and inside Myrtle Beach city limits confirm the city business license. Then check what is included: removal and disposal, interior and exterior trim, and how rot found during removal will be handled and priced.

On licensing, South Carolina’s statute lists residential specialty trades such as siding installers, carpenters, masons and painters, and window installation is not a named specialty on that list. The SC LLR Residential Builders Commission defines a residential builder as one who "constructs, superintends, or offers to construct or superintend the construction, repair, improvement, or reimprovement of a residential building" when the cost of the work is above the state’s dollar threshold. The SC LLR license lookup lets you check any contractor, and it is one of the practical reasons hiring a licensed general contractor matters.

Ask about warranties the same way you ask about ratings: in writing, and split in two. Ask which terms cover the product and which cover the installation labor, and what conditions apply to each.

What drives the cost of window replacement

The cost of window replacement in Myrtle Beach depends on the specific openings and the specific house, so a responsible estimate is built line by line rather than quoted per window from a national average. These are the factors that move the number:

Impact protection. Impact-rated glazing versus standard windows with a separate protection system.
Required ratings. Higher DP and PG values for larger openings, taller walls or more exposed locations.
Size, style and count. Oversized units, custom shapes and operable styles all change the product cost.
Frame material and energy package. Frame type, glass coatings and the U-factor and SHGC targets you choose.
Installation method. Full-frame replacement removes the whole unit, which means more work at the opening than an insert.
What turns up behind the old window. Rot in the sill or framing, or failed flashing, adds repair work.
Lead-safe practices for homes built before 1978.
Permit, inspection and access. Upper-story openings and difficult access add time.

Timing follows the same logic. The timeline depends on the product, the number of openings and what the crew finds on removal, so it belongs in the written estimate.

Top GM Construction follows the same six steps on every project: Initial Consultation, Detailed Estimate, Contract Signing, Pre-Construction Meeting, Execution and Final Walkthrough. For windows, that order means the estimate comes before the contract, which is the point to run through the checklist above. The same sequence applies whether window repair and replacement is the only item on your list or one of several remodeling services you are planning together.

Frequently asked questions

Are impact windows required in Myrtle Beach?

Impact windows, or another approved protection system, are required in Myrtle Beach where a property is inside a windborne debris region, and the local building official determines that for each address. Section R301.2.1.2 of the 2021 South Carolina Residential Code requires exterior glazing in those regions to be protected from windborne debris, either with impact-rated windows tested to ASTM E1886 and E1996 or with an approved protection system such as shutters or code-compliant wood structural panels. The state’s wind map places the Horry County coast in the highest wind bands, so ask the permit office before choosing products.

Do I need a permit to replace windows in Horry County?

Plan on a permit to replace windows in Horry County, South Carolina. Section R105.1 of the 2021 South Carolina Residential Code requires a permit to alter or repair a building, and window replacement is not on the exempt-work list in section R105.2. Horry County’s permit page does not list window replacement as exempt either, and the City of Myrtle Beach says "the answer, generally, is ‘yes,’ but exceptions exist." Confirm with Horry County Code Enforcement or your city’s building department before work starts.

What is the difference between DP and PG on a window label?

On a window label, DP (design pressure) is the wind load in pounds per square foot the window is rated to resist, while PG (performance grade) is a rating that also required passing a water penetration test. According to FEMA’s 2023 Hurricane Ian Recovery Advisory 3, the DP rating "is not always an indication of water penetration resistance" and PG is the important designation for water. FEMA recommends windows whose PG rating equals the positive DP rating, a check worth making on any bid for a Myrtle Beach home.

Is insert or full-frame replacement better?

Full-frame replacement is the better choice for a window with signs of leaks or rot, because removing the whole unit exposes the opening so it can be repaired, re-flashed and fitted with a sill pan. Insert replacement sets a new window within or over the existing frame (AAMA 2410 is the industry practice for flush-fin retrofit windows installed over a pre-existing frame) and can work well when that frame is sound and dry. For a Myrtle Beach home, the installer should explain the choice for each opening.

What energy ratings should I look for in Myrtle Beach?

In Myrtle Beach, look for a low U-factor (heat moving through the window) and a low SHGC (solar heat coming through) on the window’s NFRC label. Horry County is climate zone 3A in the South Carolina Energy Code, which lists a maximum U-factor of 0.50 and SHGC of 0.30 for zone 3. ENERGY STAR sets tighter targets by its own climate zones, so check its map for your ZIP code and compare products against that set.

Sources: South Carolina Residential Code 2021, sections R102.7.1, R105.1, R105.2, R301.2.1.2, R609, R703.4 and R703.4.1 (chapter 1, chapter 3, chapter 6, chapter 7) and R609.3 testing and labeling text (model IRC wording); SC Building Codes Council, code adoption, home page, wind maps and the Horry County wind map; South Carolina Energy Code 2009 (chapter 3, chapter 4) and SC Code Title 6, Chapter 10; Horry County, When to get a Building Permit; City of Myrtle Beach, Do you need a building permit for your project; City of Goose Creek, SC, Windows and Windborne Debris Protection; FEMA, Reducing Water Intrusion Through Windows and Doors, Hurricane Ian Recovery Advisory 3 (2023); FEMA P-499, Home Builder’s Guide to Coastal Construction; Building America Solution Center, FEMA Fact Sheet 6.1 and impact-rated windows and protective coverings; SC Department of Insurance, SC Safe Home; ENERGY STAR window criteria table, key product criteria and Version 7.0; EPA, Renovation, Repair and Painting Program for contractors; SC LLR Residential Builders Commission; SC Code Title 40, Chapter 59; FGIA, AAMA 2410-13 and FMA/AAMA/WDMA 2710-20.