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AG Millworks

Looking for project inspiration, before and afters, FAQs, and expert advice? You've come to the right place! Explore the blog to learn more about our folding, sliding, and swing door systems.

Choose the Right Patio Door Sill
Saturday, April 12 2014



A sill is that thing you step over (sometimes referred to as a threshold) when you pass through a door opening. You may never notice it, but the sill plays an important role in weatherproofing any doorway that leads into your home. Almost every swinging door has a sill of some sort, with good reason. In order for a door to swing or slide freely, there must be a certain amount of airspace around the perimeter, and therefore, a gap where air and water could conceivably penetrate and enter the interior spaces of your home, especially at the base of the door. A raised sill creates a barrier to keep any water that may collect around the base of the door from entering your home during a driving rain storm. Important, right?


Well now consider your patio door sill. Patio door openings can range from 5 feet to up to 50 feet or more in width and up to 12-feet in height. That’s a lot of wide open space; and patio doors are often positioned on the most exposed elevation of your house. It is important to consider whether you need a raised sill as a water barrier, or if the opening has enough protection to consider a sleek, recessed track system or recessed channel system for your masterpiece of indoor/outdoor living.


For a Bi-Folding patio door you have three sill/no sill options.


1.      A Raised Sill made from aluminum or wood with a built-in weep system to collect water and divert it to the exterior through the front of the sill. A raised sill offers the very best protection from water penetration, but with a 2” tall dam on the interior face of the sill, this thing is hard to miss, and you and your guests have to step over it when passing through the doorway.

2.      A Raised ADA Sill in aluminum with no weep system, which requires a 1″ wide x ½” deep channel be cut into the concrete to install it. Although this option is required in commercial applications and is needed in a home where a wheelchair is part of daily life, this sill has no dam to stop water and no weep system, so is not appropriate where weather exposure is a problem.

3.      A Recessed Channel—this option requires that a 1” wide x ¾” deep channel be cut into the concrete. An aluminum “u” channel is fixed into the cutout and the top of it sits perfectly flush with the finished floor. This gives you the most unobstructed indoor/outdoor appearance and nothing to step over or trip over. A recessed channel has no weep system and offers absolutely no protection against water entering the house, since there is no dam to keep water out and is really only appropriate where rain and garden hoses can never hit this door. Only stone, tile, or other water- resistant flooring material should be used to the inside of any door that does not have a raised sill—never wood, which would be damaged by any water that might find its way into the house.


For a Lift and Slide Patio Door or Multi-Slide Patio Door, you have two options, one with a sill, and one with tracks only.


1.      A Raised Sill made from aluminum or wood with a raised track set into it for each sliding door panel. The raised sill has a 2” dam on the interior so it provides superior protection against water penetration.

2.      A Stainless Steel Recessed Track System that is concealed beneath the finished floor, so the only thing visible after flooring is installed is a ¼” x 1/8” strip of stainless steel for each active door panel. A stainless steel recessed track system is great for openings with no weather exposure, and gives you an almost completely unobstructed floor with no sill to step over, but offers absolutely no protection against water penetration.


Before you purchase your AG Millworks patio doors, your sash and door supplier and builder will help you choose the right sill option for your patio doors and AG Millworks will build your patio doors exactly as you specify them. So what are you waiting for? Let’s get your patio door into production!

Just click here: Match me with a Dealer


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    About us

    Welcome to AG Millworks, where we combine extraordinary designs with traditional old world craftsmanship and innovation to produce ageless millwork creations that will bring your building project to life.

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    Phone:  (805) 644-4494
    3111 Golf Course Drive
    Ventura, California 93003