Learn how to measure for a Larson replacement storm door, including opening width, height, mounting surface, hinge side, handle clearance, and out-of-square conditions.
Larson Storm Door Measuring Guide
How to Measure for a Replacement Storm Door
A storm door must fit the exterior mounting surface—not simply match the entry-door slab behind it. Contractors measuring homes in Davenport, Bettendorf, and the Quad Cities should document the opening at multiple points, verify the mounting rails have a sound and flat surface, and confirm hinge, handle, closer, and trim clearances before ordering.
The Most Important Rule: Measure the Storm-Door Opening
Storm doors typically attach to exterior trim surrounding the entry door. Measure the clear opening where the storm-door frame will install, from the inside edge of one mounting surface to the other and from the top mounting surface to the threshold. Do not use the entry-door slab dimension as a substitute.
Product specifications, size ranges, and required mounting surfaces can change. Always compare field measurements with the current instructions and sizing chart for the exact Larson model being ordered.
Measurements and Conditions to Record
| Field Item | Where to Check | Why It Matters |
|---|---|---|
| Opening width | Top, middle, and bottom | Reveals taper and out-of-square trim |
| Opening height | Left, center, and right | Identifies slope and usable height |
| Mounting surface | Head and both sides | Must support rails and fasteners |
| Trim depth | Around the full perimeter | Affects handle and frame clearance |
| Hinge side | Viewed from the exterior | Controls swing and hardware position |
| Obstructions | Handle, light, wall, railing, and soffit | Prevents operating conflicts |
Tools for a Reliable Storm-Door Measure
- Tape measure capable of spanning the full opening
- Long level and shorter torpedo level
- Framing square or diagonal-measure worksheet
- Rigid rule for mounting-surface depth
- Camera for straight-on and close-up photographs
- Current Larson measuring guide and model information
Write dimensions in the same order every time—width first, then height—and clearly mark inches. A quick unlabeled number in a phone is not enough protection against a wrong-size order.
1. Identify the Actual Mounting Surface
Locate the flat exterior trim face that will receive the storm-door rails and head frame. It must be wide enough for the selected system, deep enough to keep hardware clear, and structurally sound enough to hold fasteners. Decorative profiles, capped trim, rotted brickmould, proud masonry, or uneven cladding can reduce the usable surface.
Do not assume aluminum-wrapped trim is sound underneath. Probe questionable areas carefully and document movement, soft wood, open joints, and evidence of water entry. A new storm door should not be fastened over concealed deterioration.
2. Measure Width at the Top, Middle, and Bottom
Measure horizontally between the inside edges of the left and right mounting surfaces. Take readings near the top, at the center, and near the bottom. Keep the tape level and record all three numbers rather than averaging them.
Differences reveal tapered trim, a racked opening, or a previous installation that was built around an irregular frame. Compare the complete set of readings—not merely the smallest—with the permitted opening range for the chosen storm door.
3. Measure Height on the Left, Center, and Right
Measure from the underside of the top mounting surface to the point on the sill or threshold specified by the manufacturer. Take measurements at both sides and the center. Note whether the threshold slopes, bows, or includes a raised cap that changes the landing point.
A porch surface is not automatically the correct lower reference. The storm door’s sweep and expander must meet the intended threshold while clearing the exterior surface throughout the swing.
4. Check the Opening for Square, Plumb, and Level
Compare diagonal measurements and use a level on both side mounting surfaces and the head. A slight variation may fall within the adjustable range of the selected system; a severe variation can prevent consistent reveals, reliable latching, and proper sweep contact.
Do not force a rectangular door into a visibly distorted opening. Correct loose, bowed, or deteriorated trim first. The finished installation should have balanced sightlines, an even head gap, straight mounting rails, and a sweep that does not climb sharply from one side to the other.
5. Confirm the Hinge Side and Swing Path
Viewed from the exterior, record whether the storm door will hinge on the left or right. The preferred side often coordinates with the entry door, stairs, walking path, porch layout, railing, wind exposure, and location of the primary-door handle.
- Make sure the storm-door handle will not collide with the entry-door handleset.
- Check that the closer has room to mount and operate.
- Confirm the open door will not strike a wall, light fixture, post, or railing.
- Consider how occupants approach the opening with groceries, tools, or mobility devices.
- Document the intended hinge side in words and photographs.
6. Check Handle and Primary-Door Clearance
Measure the distance between the storm-door mounting plane and the entry-door hardware. Lever handles, large escutcheons, smart locks, and projecting handlesets may interfere even when the opening size is correct. Also check decorative glass frames, mail slots, knocker hardware, and applied trim.
This clearance check is especially important with full-glass designs, where clean sightlines make an awkward hardware conflict highly visible. Contractors can compare Larson full-glass storm doors and Larson full-view storm-door styles while planning the opening.
7. Match the Door Style to How the Home Will Use It
Measurement establishes fit, but lifestyle determines the right configuration. A household that frequently changes between glass and screen has different priorities from one that wants convenient ventilation, maximum glass, or added security.
For convenient seasonal airflow, review Larson venting storm doors or Larson Screen Away storm doors. Where security is a leading requirement, compare the opening and hardware needs of the Larson Platinum Secure Screen.
8. Inspect the Threshold, Trim, and Water-Management Details
Look for rot, peeling finishes, open trim joints, failed sealant, loose threshold components, and staining. A storm door is not a repair for an actively leaking entry opening. Correct the source and restore a secure mounting surface before installation.
Do not seal drainage paths indiscriminately. The entry door, sill, flashing, trim, cladding, and storm door must function together. Follow the current instructions for approved sealant locations and fastener placement.
Final Pre-Order Checklist
- Confirm the exact Larson model and current size chart.
- Record width at the top, middle, and bottom.
- Record height at the left, center, and right.
- Verify square, plumb, level, and threshold slope.
- Measure the usable mounting surface on all three sides.
- Confirm hinge side, swing path, and closer clearance.
- Check storm-door handle clearance against primary-door hardware.
- Document trim deterioration, water damage, and required repairs.
- Confirm color, glass, screen, ventilation, hardware, and security options.
- Review photographs and measurements before submitting the order.
For product selection and current availability in eastern Iowa and the Quad Cities, request a Larson storm-door quote from Suburban Wholesale & Supply.
Common Measuring Mistakes
- Using the entry-door slab size as the storm-door opening size
- Taking only one width and one height measurement
- Measuring between decorative edges instead of usable mounting surfaces
- Ignoring an out-of-square opening because the old door operated
- Failing to check handle-to-handle interference
- Choosing hinge side without evaluating the walking path
- Fastening over loose aluminum wrap or rotted brickmould
- Ordering from an old size chart rather than current model instructions
Frequently Asked Questions
Where do you measure for a replacement storm door?
Measure the clear opening between the exterior mounting surfaces where the storm-door frame will attach, plus the height from the head mounting surface to the manufacturer-specified threshold point.
Should storm-door width be measured in three places?
Yes. Measure at the top, middle, and bottom because exterior trim can taper or move. Record all three dimensions and compare them with the current sizing chart.
How do I choose the hinge side for a storm door?
Viewed from outside, choose the side that supports a natural walking path and avoids conflicts with the entry-door handle, walls, railings, lights, and other obstructions.
Can a storm door fit an out-of-square opening?
Minor variation may be adjustable within the product’s limits, but a substantially distorted opening should be corrected before installation. Confirm acceptable tolerances in the instructions for the selected model.
Can I install a storm door over aluminum-wrapped trim?
Only when the underlying trim is structurally sound and the complete mounting condition meets the manufacturer’s requirements. Aluminum wrap alone should not be assumed to provide adequate fastening support.
A Clean Installation Begins With an Honest Measure
The wrong question is, “What size was the old storm door?” The right question is, “What does this opening support now?” Measuring every side, confronting irregularities, and confirming hardware clearances produces a storm door that operates smoothly and frames the entry with balanced, professional lines.
Contractor Notes
We‘re here to help.
Suburban Wholesale & Supply works with contractors, remodelers, builders, and property professionals across Davenport, Bettendorf, Moline, Rock Island, and the wider Quad Cities. If How to Measure for a Replacement Storm Door affects a project you are pricing, our team can help compare product lines, confirm available options, and prepare a quote that fits the opening, exterior, or jobsite requirements.
Our counter and showroom teams support window, patio door, entry door, storm door, siding, trim coil, gutter protection, and accessory orders every week. We can talk through manufacturer differences, color and finish selections, installation details, lead times, and documentation so you can give your customer clear answers before the work begins.
For current availability, contractor pricing, product literature, or help matching this topic to a real project, contact Suburban Wholesale & Supply or send the details through our quote form. We will help you move from product research to an accurate material order with fewer surprises.
Share This Post
Share it on Facebook or X, or send it through your device share sheet for Instagram.