STOP WATER UNDER YOUR PATIO DOOR: WHAT’S REALLY GOING ON
Puddles by the threshold, swollen boards, chilly draughts and a musty smell are classic signs of water finding its way under your patio door. It’s rarely the glass unit. Most leaks start at the threshold: blocked tracks or weep holes, tired silicone, failed gaskets, missing end caps, or doors sitting slightly out of line. Sliding and French doors can both suffer, but the leak paths differ around the track and corners.
The good news: these faults are usually repairable, quickly and affordably. A tidy repair protects floors and skirting, restores seal contact and helps keep energy bills down—without the cost and disruption of a new door. For a broader overview of door types and fixes, see our patio doors guide. We take a repair-first approach wherever it’s safe and sensible, helping you avoid premature replacements.
QUICK CHECKS YOU CAN DO BEFORE WE ARRIVE
- After rain, run tissue along the inside cill and both bottom corners of the frame. Fresh damp marks point to threshold ingress.
- Outside, pour a small amount of water onto the outer track from a watering can. It should drain through weep holes within seconds. Slow or no flow means a blockage.
- Differentiate leaks from condensation: moisture on panes and beads without pooling at the threshold is usually condensation. See 5 quick fixes to stop window condensation.
- For a faster quote, take clear photos or a short video of both bottom corners, the full threshold, outside silicone lines and the weep holes.
THRESHOLDS, TRACKS AND WEEP HOLES—HOW DRAINAGE SHOULD WORK
At the base of a typical uPVC or aluminium sliding door you’ll see an outer track (rain zone) and an inner track (room side), with a threshold cover and end caps. Rain is designed to enter the outer track, then escape through weep holes and a sub-sill. If that flow is blocked, water takes the path of least resistance—often indoors at the corners.
A healthy setup has clean channels, clear weep holes, intact end caps and a sound external silicone bead. On worn doors, gaskets can flatten or perish, and missing end caps let water roll sideways into the frame. If your rollers or track need attention, see our guide to sliding patio door roller and track repairs. For tired gaskets and seals, we offer gasket and seal replacements that restore compression and stop leaks.
This image was generated with AI and may not always represent the product or service exactly.
THE USUAL CULPRITS CAUSING WATER UNDER DOORS
- Blocked weep holes and outer tracks (grit, pet hair, algae) cause water to back up and spill inboard.
- Flattened threshold gaskets and corner seals create capillary paths for wind‑driven rain.
- Missing or loose end caps let water run along the frame and into the inner track.
- Cracked, shrunk or patchy external silicone—especially at bottom corners and cill/brick joints—admits water.
- Door misalignment reduces seal compression; common after seasonal movement and usually a simple adjustment.
AFFORDABLE FIXES FOR SLIDING PATIO DOORS
- Restore drainage: deep clean the track, clear weep holes and flush the sub-sill.
- Refit/replace threshold end caps and add discreet drip trims where helpful.
- Re-silicone key external joints to stop wind‑driven rain.
- Set the sash up to seal: adjust roller height and alignment so the door sits square and drains correctly.
These steps often stop the leak and improve the slide, comfort and energy efficiency. For pricing context on track and roller work, see sliding patio door roller and track repairs (UK costs).
AFFORDABLE FIXES FOR FRENCH DOORS AND SIDE PANELS
- Renew the bottom weather bar and threshold seals; upgrade compression gaskets.
- Re-silicone external joints along the cill, frame perimeter and mullions for a continuous barrier.
- Adjust hinges to lift and pull doors back into square for even seal contact.
- Toe-and-heel glazing in dropped sashes or side panels to prevent sag and maintain compression.
New gaskets make a big difference to draughts and leaks—see our gasket seal repairs and replacements page for options we carry.
WHEN LEAKS POINT TO BIGGER ISSUES
- Spongy or rotten timber sub-sill, a sunken cill or a visibly twisted/warped frame.
- Patio level or internal floor bridging the damp‑proof course (DPC), or cill set too low.
- Poorly sealed junctions behind trims, or render/tiles bridging the frame drainage paths.
We still start with the least invasive repair to buy time and reduce damage, then set out your options. If storms have driven water under the frame, photograph the damage, keep receipts, and note dates and weather conditions. Our guide to documenting window and door damage after a storm explains what insurers look for. If a frame section needs work, we’ll advise on the best‑value repair versus replacement route.
This image was generated with AI and may not always represent the product or service exactly.
PREVENT LEAKS WITH SIMPLE MAINTENANCE
- Twice a year, brush out the outer track and weep holes; wash with mild detergent and warm water, then rinse.
- Do not force debris down weep holes—flush gently until water runs freely outside.
- Annually, inspect external silicone around the frame and along the cill; renew early if you see cracks or gaps, especially at bottom corners.
- Keep mats, planters and gravel clear of drainage paths so weep holes can breathe.
A 20–30 minute clean each spring and autumn can prevent callouts and protect floors and skirting.
COSTS, TIMELINES AND WHAT WE DO ON THE DAY
Typical guide prices (inc. labour, ex. parts where noted):
- Track clean and unblock: £60–£120
- External re-silicone to bottom frame/cill joints: £80–£180
- New threshold gaskets or end caps: £25–£75 for parts + £40–£90 fitting
- Roller or hinge adjustments: £65–£140
Exact cost depends on door type, size and condition.
- On the day we assess the door, confirm pricing, carry out the repair, water‑test from outside and tidy up.
- We stock common end caps, gaskets and trims for same‑day fixes.
- You’ll get simple aftercare tips and a clear note of any future work to consider.
BOOK LOCAL PATIO DOOR REPAIRS TODAY
Plastic Doctor covers homes across Essex and Suffolk with fast appointments. Many patio door leaks are fixed in one visit. Send photos for a quick estimate or book a convenient slot. Use contact us to get started.
We can also sort gaskets, locks and handles while we’re there, plus general alignment. If you’re a landlord, we handle tenanted properties with minimal disruption and clear updates. For local support in north Essex, see our page for door repairs in Colchester.
FAQs
Why does my patio door only leak in heavy rain?
Blocked weep holes or weak corner sealing can cope in light rain but fail under volume or wind‑driven conditions. Restoring drainage and renewing the external bead usually solves it.
Is silicone inside the frame a good fix?
No. Internal silicone can trap water and send it elsewhere. The right fix is to restore external drainage and sealing so water exits outside as designed.
Will you need to remove my door to fix a threshold leak?
Usually not. Most repairs are done with the door in place. We may lift a sliding sash briefly to adjust rollers or refit end caps.
How long do repairs take?
Simple cleans and re‑seals take 45–90 minutes. Add time for roller or hinge adjustments. We aim to water‑test and finish in a single visit.
Do you carry parts for older uPVC or aluminium doors?
Yes. We stock common gaskets, end caps and trims, plus universal options for older systems. If something is specific, we’ll source it quickly.
Will a repair reduce draughts and energy bills?
Yes. Restored seal compression and fresh gaskets cut draughts, helping rooms feel warmer and reducing heat loss through the doorway.
Can you work at tenanted properties?
Yes. We liaise with tenants, keep disruption low and provide clear before‑and‑after photos for landlords and agents.
