Water leaking in at the sill: causes and repair cost in Myrtle Beach

Water coming in under a sliding glass door on the Grand Strand is almost never a broken door. It is a drainage problem: the sill weep holes are packed with beach sand, so the water the sill is designed to collect has nowhere to go and backs up over the interior lip. Clearing the drains and renewing the weatherstrip and interlock runs $100 to $250, and the $95 to $175 service call is applied. Only when the sill or track has corroded through does this become a $300 to $650 track replacement.

Check this first

Vacuum the whole sill. Both grooves, corner to corner. Sand, pine needles, and the grey paste that old lubricant turns into all end up in the same place.
Find the weep holes. Look along the outside face of the sill for small slots or round openings, often two or three across the width, sometimes covered by a small hinged plastic flap. Those flaps are supposed to swing open outward and close against wind. Sand jams them shut.
Flush it. With the track clean, pour a cup of water into the outer groove. It should run out the front within seconds. If it pools, work a pipe cleaner or a length of soft wire through each weep hole and flush again.
Look at the weatherstrip and interlock. The fuzzy pile along the panel edges and the interlocking stiles where the two panels meet are what keep most of the water out in the first place. Flattened, missing, or brittle pile means far more water reaching the sill than the drains were designed for.
Watch during rain if you can. Water arriving at one corner points at flashing or the wall above. Water rising evenly along the sill is drainage.

What is usually wrong

What you see	Likely cause	Fix and cost
Sill fills and spills inward in heavy rain	Weep holes blocked with sand	Clear drains, weatherstrip and interlock $100 to $250
Water only when wind drives from the ocean side	Worn pile, gapped interlock, panel sitting low	Weatherstrip $100 to $250, plus rollers $175 to $350 if the panel dropped
Steady drip at one jamb corner	Failed perimeter sealant or flashing above	Sealed and assessed on site; framing work quoted separately
Sill soft, pitted, or holed through	Salt corrosion of the aluminum sill	Full track and sill replacement, $300 to $650
Water inside the glass cavity, not on the floor	Failed insulated unit	New sealed unit, $350 to $900
Leak began right after a storm	Frame racked, sealant split	Track work $150 to $650, or replacement if the frame moved

Those ranges are published on the pricing page.

Why this is a Grand Strand problem

Two things. First, the sand: fine quartz grit blows into every open track from Cherry Grove to Litchfield, and it is exactly the size to bridge a weep hole and then set hard when it gets wet. Second, the rain. Coastal South Carolina gets tropical rainfall in bands that drive horizontally against the ocean face of a building, which is the one condition a sliding door sill is least able to shed. On September 30, 2022, Hurricane Ian came ashore near Georgetown as an 80 mph storm and pushed the tide gauge at Springmaid Pier to 10.77 feet above mean lower low water, almost a foot higher than during Isaias in 2020, according to the National Weather Service’s summary of the storm. Doors that had never leaked in ordinary weather leaked that day, and most of them needed drains and pile, not replacement.

Ground-floor lanai doors in Surfside Beach and balcony doors on the ocean face of a tower have this problem for the same reason and get the same fix. Doors in Socastee and Longs leak far less often, and when they do it is usually sealant or flashing rather than salt-blocked drains.

When replacement beats repair

A sill that has corroded through is the one clear case. Once there are holes in the bottom of the pan the water is going into the wall and the floor system, not out the front, and a track cap over a rotten sill hides it rather than fixing it. If the sill is holed, the frame is racked, or the leak is coming from the rough opening rather than the door, get numbers for full replacement, $1,500 to $4,000 non-impact and $3,000 to $6,000 impact-rated, and compare. Everything short of that is a repair.

What to expect on the call

Say where the water appears, in what wind direction, and whether the sill holds water after you pour a cup in. Photograph the sill from outside, showing the weep holes, and the interior floor where the water lands. We clear the drains, replace pile and interlock, check the panel height so the door seals against the jamb, and tells you honestly if what you have is a wall problem rather than a door problem. The repair cost estimator gives the range before anyone visits.

Frequently Asked Questions

Why is water coming in under my sliding glass door?

In most cases the sill drains are blocked. A sliding door sill is designed to collect the water that gets past the panel and drain it back outside through small weep holes at the front edge. Pack those with beach sand and old sealant and the sill fills up in a hard rain and spills inward over the interior lip.

How much does it cost to stop a sliding door leaking at the sill?

If it is weep holes and worn weatherstrip, weatherstrip, pile, and interlock work is $100 to $250 and clearing drains is part of the visit. If the sill or track is corroded through, full track replacement is $300 to $650. The $95 to $175 service call is usually applied to the repair.

Can I clear the weep holes myself?

Yes, and it is the first thing to try. The weep holes are small slots or round openings along the outside face of the sill, sometimes behind a small plastic flap. Vacuum the track, then work a soft wire or a pipe cleaner through each opening and rinse from inside the track with a bottle of water until it runs out the front.

Is water at the sill covered by insurance?

Wind-driven rain entering through a door during a named storm is treated differently by every policy, and slow leakage from blocked drains is normally maintenance, not a covered loss. Photograph the door and the wet floor with a date before anything is repaired, and read your policy or ask your agent before assuming.