How to Keep Water Out of Exterior Doors: Threshold Solutions

If you see wetness on the inside of the door after rain, the gasket gets blamed first. But the gasket's job is to block air; what stops water is the threshold setup and drainage. If water pools in front of the gasket, sooner or later it gets through — pressurized water finds every gap.

Look at how the water reaches the door

There are two distinct scenarios, with distinct solutions:

• Direct rain: with no eaves, water streams down the face of the leaf and pools at the bottom edge
• Splash-back: even with eaves, water hitting the ground bounces back and soaks the bottom 30 cm of the door

The first thing we look at during a site survey is what sits above the door. Eaves, a porch or a balcony overhang make the solution easier; without them, the threshold side needs more measures.

The drip profile

An L-section profile fitted to the bottom outer edge of the leaf that throws water clear of the door. It looks simple but its effect is large: instead of running down the face and wrapping around the bottom edge, water drops to the ground from the profile's tip. On a door without a drip profile, the bottom edge stays permanently damp and the cladding eventually blisters.

This is a hard problem to describe over the phone. Send a photo of the door and the problem area via WhatsApp to 0532 689 21 46; in most cases we can tell what's going on at a glance. If a site survey is needed, it's free.

A drainage channel in the threshold

The better aluminum threshold profiles have a slim channel in front of the surface the gasket seats on. Water reaching it is guided out along the channel and never presses on the gasket. If the channel fills with dust, leaves and grit, it stops working — it needs cleaning once a year.

Slope

If the ground in front of the door slopes toward it, no threshold solution will hold up for long. The ground needs a slight slope away from the door. On new entrances, saying so during construction is the cheapest fix; on a finished entrance, correcting the slope means floor work.

A layer-by-layer checklist

Layer	Its job	Warning sign
Eaves / porch	Keep water off the door entirely	Leaf face fully soaked after rain
Drip profile	Throw water clear of the leaf	Blistering, darkening at the bottom edge
Threshold drainage channel	Guide arriving water out	Water pooling on the threshold
Gasket	Block air and the last drop of water	Wetness inside, draftiness
Floor slope	Carry water away from the door	A puddle in front of the door

Wind-driven rain is a different load altogether

A door that stays dry in calm weather letting in water during a storm is a complaint we hear often, and it has a logical explanation. In vertical rainfall, water runs down under gravity; once wind enters the picture, it gets pressed horizontally against the gasket line. That significantly raises the force the gasket has to withstand.

On entrances facing the sea or the prevailing wind, a single run of gasket often can't hold that pressure. Two things solve it together: a double run of gaskets and multi-point locking. The second is usually assumed to be a security feature, yet it works directly for airtightness too — by pulling the leaf into the frame at several points from top to bottom rather than one, it distributes gasket compression evenly around the perimeter. With a single-bolt lock, the leaf's top and bottom corners pull away from the frame; water gets in exactly there.

That's why we note the wind direction at the site survey. The same door on the same building can be built with different gasket packages for the north and south facades.

Frequently Asked Questions

If water is getting in, is replacing the gasket enough?

Usually not. The gasket blocks air; what stops water is the threshold drainage and the drip profile. If water keeps pooling after a new gasket, the problem returns.

Can a door have no threshold?

Indoors, yes; on an exterior door it's not advisable. The threshold both provides a true surface for the gasket to seat on and directs water away. Where accessibility is needed, low-profile thresholds are used.

How often should the drainage channel be cleaned?

Once a year is enough. For entrances under trees, it's worth a second check in autumn.

Let's see your entrance

Water problems almost always trace back to a detail specific to the entrance. Send photos of the door and the ground in front of it to 0532 689 21 46; we'll tell you which layer is missing.