Sash weight is one of the most important pieces of information needed when selecting replacement window balances. The balances must provide enough support for the sash without making the window too difficult to close or allowing it to fall.

Before You Start

Tools and information you may need:

• Bathroom scale, shipping scale, or platform scale
• Original sash
• Phone or camera for reference photos
• Paper or notes app for recording the weight
• Small block or stable platform, when needed
• Work gloves and safety glasses
• A second person for a large or heavy sash
• Any balance stamps, markings, or identification numbers

Safety Warning: Window sashes may contain heavy glass and can shift unexpectedly when disconnected from their balances. Maintain control of both sides and ask for assistance when the sash is large, awkward, or difficult to remove.

Do not place your hands beneath an unsupported sash or allow the sash to drop onto the scale.

Window balances counteract the weight of a movable sash. Most vertically operating windows use one balance on each side.

The left and right balances work together as a pair. In a properly matched system, each balance supports approximately one-half of the total sash weight.

If the balances are too weak:

• The sash may fall or drift downward.
• The window may not remain open.
• The balances may wear out prematurely.
• The sash may move unevenly.

If the balances are too strong:

• The sash may be difficult to lower.
• The window may rise on its own.
• The sash may resist closing completely.
• Locks and meeting rails may become difficult to align.

Important: The sash weight helps determine the required balance capacity, but it does not identify the complete replacement by itself. Balance type, channel length, spring length, attachment style, guide configuration, and original markings may also be required.

Before weighing anything, determine whether the window is single-hung or double-hung.

Single-hung window:

• Usually has one movable lower sash.
• The upper sash is normally fixed.
• Only the movable sash requires operating balances.

Double-hung window:

• Has movable upper and lower sashes.
• Each sash normally has its own balance pair.
• The upper and lower sashes must be weighed separately.

Label the recorded weight as upper sash or lower sash so the measurements are not confused later.

1. Place the scale on a firm, level floor.
2. Do not use thick carpet or an uneven surface.
3. Turn the scale on and confirm that it reads zero.
4. Test it with an object of known weight when accuracy is uncertain.
5. Confirm that the scale’s capacity is greater than the expected sash weight.

A scale that rocks, rests on carpet, or does not return to zero may produce an inaccurate reading.

The removal procedure depends on the window and balance style.

Common sash-removal systems include:

• Tilt sashes with tilt latches, pivot bars, and pivot lock shoes
• Non-tilt sashes using block and tackle balances and take-out clips
• Spiral-balance windows using brackets or pivot shoes
• Coil-balance windows using pivot bars and locking shoes
• Wood windows using removable jamb liners or sash cords

Follow the correct removal procedure for the window. Keep the sash level and support both sides throughout removal.

Place the removed sash on a padded surface until the scale is ready.

1. Confirm that the scale reads zero.
2. Lift the sash with both hands.
3. Center the sash on the scale.
4. Make sure the complete weight is resting on the scale.
5. Keep your hands on the sash only for balance, without lifting or pressing downward.
6. Wait for the reading to stabilize.
7. Record the weight immediately.

Keep your feet, knees, tools, and nearby objects from touching the sash or scale while the reading is taken.

A sash may be wider than the weighing surface of a bathroom scale.

1. Place a rigid, stable board or platform across the scale.
2. Confirm that the board does not touch the floor.
3. Turn on or zero the scale with the board already in place when the scale supports that function.
4. If the scale cannot be zeroed, weigh the board separately.
5. Place the sash in the center of the board.
6. Subtract the board’s weight from the combined reading when necessary.

The board must remain stable and transfer the entire load to the scale without contacting another surface.

1. Remove the sash from the scale.
2. Confirm that the scale returns to zero.
3. Weigh the sash a second time.
4. Compare the two readings.
5. Repeat the process when the readings differ noticeably.

Record the confirmed weight rather than relying on a single quick reading.

Use caution: This method is less reliable because jamb friction, weatherstripping, misalignment, partially connected balances, and contact with the frame can affect the reading.

Both the left and right balance systems must be completely disconnected from the sash before it can be weighed accurately.

Depending on the window, this may involve:

• Releasing block and tackle balances from sash cams
• Disconnecting spiral-balance brackets
• Removing pivot bars from pivot lock shoes
• Disconnecting coil-balance shoes or carriers
• Releasing sash cords or chains

Once disconnected, the sash will feel much heavier because the balances are no longer supporting it.

Inspect the sash and jamb before placing the scale beneath it.

Make sure the sash is not being supported or restricted by:

• A partially connected balance
• Tight weatherstripping
• Paint buildup
• Jamb liners or guide channels
• Locks, stops, or clips
• Dirt or debris inside the track
• A bowed frame
• A sash that is rubbing heavily on one side

Any upward friction or remaining balance tension may cause the scale to display less than the sash’s true weight.

1. Raise the disconnected sash high enough to position the scale beneath it.
2. Center the scale below the sash.
3. Lower the sash slowly onto the scale.
4. Keep both sides level.
5. Do not press downward or lift upward while reading the scale.
6. Allow the number to stabilize.
7. Record the result.

Maintain control so the sash does not drop, tilt, twist, or slide off the scale.

Take the reading more than once and watch for inconsistent results.

A questionable reading may be indicated by:

• The number changing when the sash is moved slightly
• Different readings from repeated attempts
• The sash visibly rubbing against the jamb
• One side appearing lighter or higher than the other
• Remaining tension from a balance or cord
• The scale rocking or sitting unevenly

When the in-frame reading cannot be confirmed confidently, remove the sash and weigh it directly.

A double-hung window has separate balance systems for the upper and lower sashes.

1. Remove and weigh the lower sash.
2. Label the recorded weight as lower sash.
3. Remove and weigh the upper sash separately.
4. Label that result as upper sash.
5. Record the balance markings associated with each sash.

Do not add the upper- and lower-sash weights together. Each sash requires a balance pair selected for its own weight.

Record the full scale reading rather than rounding immediately to the nearest whole pound.

Include:

• Total sash weight
• Pounds and ounces, or pounds with a decimal
• Whether the weight belongs to the upper or lower sash
• Whether the sash was removed or weighed in place
• The type of scale used
• Any uncertainty caused by friction or limited access

When recording pounds and ounces, remember that 16 ounces equals one pound.

Preserve the original measurement in your notes even when a product chart groups the sash into a broader weight range.

Vertically operating windows commonly use two balances—one on the left and one on the right.

Together, the pair supports the complete sash. Each balance generally contributes approximately half of the required support.

Do not divide the sash weight and then order a balance using only that number unless the product instructions specifically request capacity per balance. Many replacement charts list the sash-weight range supported by the complete balance pair.

Use the product chart as written: Confirm whether a published weight range refers to one balance or the installed pair. Do not assume all manufacturers label balance capacity the same way.

Sash weight should be documented with the original balance information whenever possible.

Record:

• Balance type
• Metal-channel or tube length
• Channel width and depth
• Spring length, when required
• Stamp, code, tip color, or coil marking
• Top and bottom guide style
• Shoe, bracket, hook, or clip configuration
• Left- and right-side orientation
• Photos of the complete original balance

Clear photos can help connect the sash weight to the correct balance system.

Include photos of:

• The complete window from the interior
• The sash removed from the opening
• The sash positioned on the scale
• The stabilized scale reading
• The complete balance from both sides
• All stamps, numbers, colors, and markings
• The upper and lower balance attachments
• The jamb where the balance was installed
• The sash connection point

• Using a scale on carpet or an uneven floor
• Failing to confirm that the scale reads zero
• Holding part of the sash weight while reading the scale
• Pressing downward on the sash
• Allowing the sash to touch the floor, wall, jamb, or another object
• Leaving one or both balances connected
• Ignoring jamb and weatherstripping friction
• Combining the upper- and lower-sash weights
• Forgetting to subtract the weight of a support board
• Rounding the result too aggressively
• Relying on one unstable reading
• Selecting a balance by sash weight alone
• Discarding the original balances before confirming replacements

Before selecting replacement balances, confirm:

• The correct movable sash has been identified.
• Upper and lower sashes were weighed separately.
• The scale was placed on a hard, level surface.
• The scale was checked for zero.
• The complete sash weight rested on the scale.
• The reading was confirmed at least twice.
• Any platform weight was removed from the result.
• The exact weight was recorded.
• The balance type and length were documented.
• All original balance stamps and attachments were photographed.
• The product chart’s weight-rating method was confirmed.

The most reliable way to determine sash weight is to remove the sash and place its complete weight on a level, properly zeroed scale.

When weighing a sash inside the frame, disconnect both balances and eliminate as much jamb friction as possible. Treat the result cautiously and repeat the measurement.

On a double-hung window, weigh the upper and lower sashes separately. Use the confirmed sash weight together with the balance type, length, stamp, attachment style, and manufacturer specifications to identify the correct replacements.