Window Security for California Homes

Window security is usually sold as a product: a film, a bar, a "security window." It works better treated as a sequence. A burglar looking at a window wants it to open quickly and quietly, so the job is to remove the quick, quiet options one at a time, starting with the cheapest. This page goes through them in that order. It is part of our California window guide.

Start with what costs nothing

• Lock them. An unlocked window offers no resistance at all. Windows left open a few inches for air on a summer night in Sacramento are the classic case.
• Check that the lock engages. On an older window whose sashes have sagged or whose frame has moved, the latch can look closed without catching the keeper.
• Look at the window from outside. Can it be reached from the ground, a fence, a trash bin, an air-conditioner pad or a low roof? Is it hidden from the street and the neighbors?
• Trim the cover. A window behind a tall hedge gives someone time to work.

Locks and latches by window type

How a window locks depends on how it opens, and the types are not equal.

A casement with a multi-point lock is among the hardest common windows to pry, because the sash is clamped into the frame along its edge and there is no meeting rail to work at. A sliding window is among the easiest, which is why sliders get their own section below. If you are choosing styles, see how to choose a window style.

Sliders and the lift-out problem

California is slider country. Millions of tract houses were built with aluminum horizontal sliding windows and sliding patio doors, and the design has a built-in weakness: the sash sits in a bottom track and is held in at the top only by a channel with enough clearance to let it be installed. If there is too much clearance, a closed and latched sash can be lifted until its bottom edge clears the track, then swung out.

The fixes are simple:

1. Anti-lift blocks. A block or screws in the upper track above the closed sash, set so the sash still slides but cannot be raised. Many current windows include these from the factory.
2. A secondary lock. A pin through the overlapping frames, a keyed track lock or a clamp-on stop. It also lets you fix the window a few inches open.
3. A bar or dowel in the bottom track. Crude and effective against sliding, though it does nothing about lifting.

If you have original single-pane aluminum sliders, the latch, the track and the glass are all weak, and that is a fair reason to put those windows first in a replacement plan. Our page on sliding windows covers the current designs, and a separate guide covers sliding patio door replacement.

Glass: tempered is for safety, laminated is for security

This is the most misunderstood point in window security.

Tempered glass is heat-treated to be stronger than ordinary annealed glass, and when it breaks it breaks completely, into small granular pieces. That is the purpose: it is safety glazing, intended to reduce cutting injuries, and the code requires it in specific hazardous locations such as doors, glass next to doors, and glass near the floor or a tub. But a broken tempered pane leaves nothing in the opening. A center punch defeats it in a second.

Laminated glass is two sheets of glass bonded to a plastic interlayer, like a car windshield. When it breaks, the fragments stay stuck to the interlayer and the pane stays in the frame. Getting through takes repeated blows, time and noise. That delay is what security is.

Both types can qualify as safety glazing. The 2025 California Residential Code, Section R324 (formerly R308), requires safety glazing in hazardous locations to meet the federal standard at 16 CFR 1201 or ANSI Z97.1, and laminated products are tested to the same standards. So laminated glass can go where tempered is required, if it carries the right marking. Our page on California tempered glass requirements lists the locations.

Laminated glass in an insulated window brings a side benefit: it is also one of the standard ways to cut noise (see types of soundproof windows). Its cost is weight and price, so most homeowners use it selectively: ground-floor windows out of sight, sidelights beside an entry door, and glass within reach of a door lock. Other glass options are at types of window glass.

What forced-entry ratings mean

If a window brochure mentions forced-entry resistance, it is referring to one of these.

ASTM F588

The current forced-entry test for windows is ASTM F588, "Standard Test Methods for Measuring the Forced Entry Resistance of Window Assemblies, Excluding Glazing Impact." The current edition is F588-26. It simulates the methods of unskilled or opportunistic burglars, with loads and simple tools applied to the sash, frame and hardware, and it assigns a performance grade of 10, 20, 30 or 40, with 40 the most resistant.

Read the title again: excluding glazing impact. An F588 grade tells you the sash cannot easily be pried, lifted or manipulated open. It tells you nothing about what happens when someone hits the glass.

NAFS

The North American Fenestration Standard (AAMA/WDMA/CSA 101/I.S.2/A440) is the general performance standard windows are certified to for air, water and structural load. It incorporates forced-entry testing, and operable windows certified to NAFS are typically tested to F588 at Grade 10 where the test applies. So most certified windows from reputable manufacturers have passed the basic grade. Few are tested higher, and a higher grade is worth asking about for a vulnerable opening.

The obsolete references

You will still find AAMA 1302.5 and CAWM 301 cited on websites and in old spec sheets. Both are obsolete. A current product should point to ASTM F588 or to NAFS.

One practical note: a rating applies to the window as tested. It does not survive a poor installation. A frame that is not fastened properly into the opening can be forced as a unit, whatever its grade.

Security film

Security film is a thick polyester film applied to the inside face of existing glass. When the glass breaks, the film holds the pieces together and the pane tends to stay in place for a time.

• It delays; it does not stop. Film buys seconds to minutes depending on thickness and on how it is attached.
• Edge attachment matters. Film that stops at the visible edge of the glass can be pushed in as a sheet once the glass is broken. Systems that anchor the film to the frame hold much better.
• Check the claim. Films can be tested to safety glazing standards such as ANSI Z97.1 and 16 CFR 1201. Ask which standard a product was tested to and on what glass.
• Check the glass warranty. Film on an insulated glass unit changes how the glass heats in the sun, and many window manufacturers exclude it. Our page on window film versus window replacement covers that.

Film makes sense on sound existing windows you are not replacing. If you are buying new windows, specify laminated glass instead.

Bars and grilles: the egress rule

Bars stop entry. They can also stop exit, and in a house fire that is the greater danger. California's rules exist for that reason.

• Escape windows must stay usable. Bedrooms need an emergency escape and rescue opening. Under Section R319.4.4 of the 2025 California Residential Code (the section was R310 in earlier editions), bars, grilles, covers or screens placed over one must be releasable or removable from the inside without the use of a key or tool, or force greater than normal operation of the opening, and the release mechanism must be maintained operable at all times.
• The hardware must be approved. Health and Safety Code section 13114.2 prohibits installing, marketing or selling burglar bars and safety release mechanisms for emergency escape windows or doors in California unless they have been approved by a testing laboratory recognized by the State Fire Marshal. The State Fire Marshal's standards for release systems are in Title 24, Part 12.
• Old bars are the danger. Fixed bars welded or bolted over a bedroom window, with no release or with a padlock, are the ones to deal with. If you buy a house with them, treat it as a safety repair.

The same principle applies to anything else across an escape window: a security screen, a fixed secondary lock that needs a key, or a window painted or screwed shut. Our page on egress window regulations covers the opening sizes; note that current code numbers these rules R319.

Security must also not defeat child safety. Devices that limit how far a window opens are covered in window fall prevention and child safety.

Rentals, briefly

California Civil Code section 1941.3 has required landlords, since 1 July 1998, to install and maintain operable window security or locking devices on windows that are designed to be opened. Louvered and casement windows are excluded, as are windows more than 12 feet vertically or 6 feet horizontally from the ground, a roof or any other platform. The same section requires a deadbolt on each main swinging entry door. Tenants are responsible for telling the landlord when a lock is inoperable, and the landlord's liability turns on failing to fix it within a reasonable time after notice.

The owner's side of this is in landlord window obligations in California, and our work for owners is described on the property managers page.

Sensors and alarms

A contact sensor tells you a window has been opened, and a glass-break sensor that it has been smashed. Neither makes the window harder to get through, but both shorten the time an intruder is willing to stay. Built-in and add-on options are described in smart glass and motorized windows.

A priority order

1. Lock every window, and fix any that do not latch.
2. Add anti-lift protection and secondary locks to sliders.
3. Deal with any fixed bars over bedroom windows.
4. Add sensors if you have or want an alarm.
5. Put security film on vulnerable existing glass you are keeping.
6. When replacing, choose laminated glass and better locking hardware for hidden ground-floor openings, and ask what forced-entry grade the product was tested to.

Most houses get most of the benefit from the first three, which cost very little.

Sources

• ASTM International: F588, Standard Test Methods for Measuring the Forced Entry Resistance of Window Assemblies, Excluding Glazing Impact
• California Civil Code section 1941.3
• California Health and Safety Code section 13114.2
• 2025 California Residential Code, Chapter 3, Sections R319 (emergency escape and rescue openings) and R324 (glazing)
• 16 CFR Part 1201, Safety Standard for Architectural Glazing Materials

Working with Heritage Exteriors

We will check the locks, tracks and glass on your existing windows and tell you which ones a secondary lock would fix and which are worth replacing. When we quote new windows for an exposed opening, we will price laminated glass as an option and tell you what forced-entry grade the manufacturer publishes for the product. Licensed in California, CSLB #1055919. Call (916) 546-2991.