Quick Answer: To measure mattress sag for a warranty claim, place a rigid straight edge (broomstick or level) across the indented area and measure the deepest point without applying body weight. Most Canadian manufacturers require a minimum of 1.5 inches of indentation. Photograph everything with a ruler visible. Keep your original receipt.
In This Guide
Reading Time: 7 minutes
Mattress warranties are written by manufacturers, not by customers. That distinction matters more than most people realize until they are standing over a mattress that has clearly softened or sagged and trying to figure out whether it qualifies for a warranty claim.
At Mattress Miracle, we have helped Brantford customers navigate warranty claims since 1987. Brad, our senior consultant, puts it bluntly: "The warranty language is designed to protect the manufacturer. To make a successful claim, you need to understand their measurement criteria and document everything before you call."
This guide covers how to measure mattress sag correctly, what the thresholds typically are, which foundations and frame setups can void a claim, and what documentation you need to build a defensible case.
What Counts as Warrantable Sag
The most important thing to understand about mattress warranties in Canada is that they cover manufacturing defects, not normal wear. The distinction between "defect" and "wear" is where most claims get complicated.
The Indentation Test: How Manufacturers Measure
Manufacturers measure sagging with the mattress unloaded (no body weight, no bedding on it) using a rigid straight edge placed across the mattress surface. The measurement is the vertical distance from the bottom of the straight edge to the deepest point of the indentation. This is called "body impression depth" or "indentation depth." Most Canadian mattress manufacturers set their warranty threshold at 1.5 inches (approximately 38 mm) of indentation depth, measured unloaded. Some premium manufacturers use a 1-inch threshold. Some budget lines use 2 inches. The threshold varies by brand, product line, and warranty tier.
What this means practically: a mattress that feels significantly softer than when you bought it, but measures only 1.2 inches of indentation unloaded, typically does not qualify for a warranty claim under a 1.5-inch threshold warranty. The foam has softened (IFD decay, which is a normal material property change over time), but the visible indentation depth is below the threshold.
This is a genuine gap in consumer protection that the warranty language exploits. Perceived comfort loss is real; the measurement threshold exists independently of how the mattress feels.
How to Measure Mattress Sag: Step-by-Step
How to Measure Mattress Sagging for a Warranty Claim
Step 1: Clear the Mattress Completely
Remove all bedding, pillows, mattress protectors, and toppers. The mattress must be bare. Leave it unloaded for at least 30 minutes before measuring. Some foam types partially recover when pressure is removed. Measuring immediately after getting out of bed can give artificially high readings that work in your favour but can also be challenged by the manufacturer.
Step 2: Locate the Deepest Indentation Points
Look at the mattress from the side while it is on its foundation. Typical sag locations are where your hips and shoulders rest most often. On a shared mattress, there are often two separate sag zones. Identify the deepest-looking indentation visually before measuring. You will want to measure at the absolute deepest point, not an average across the surface.
Step 3: Place a Rigid Straight Edge Across the Indentation
Use a broomstick, a rigid yardstick (not a flexible tape measure), a carpenter's level, or a length of straight lumber. The straight edge must span from one unaffected area of the mattress to another, bridging the sagged zone. If the straight edge itself bends or flexes, your measurement will be inaccurate. A 4-foot level from a hardware store works well for most queen and king measurements.
Step 4: Measure the Gap
With the straight edge resting on the mattress surface on both sides of the indentation, use a ruler or measuring tape held vertically to measure the distance from the bottom of the straight edge to the lowest point of the mattress surface. This is your indentation depth. Take measurements at two or three points within the sag zone and use the deepest reading.
Step 5: Photograph Everything
Take photographs that show: the mattress bare (full width and length from above), the straight edge in position across the sag, and the ruler showing the measurement depth. Include a handwritten note with the date in at least one photograph. Take photos from multiple angles. Bright side-lighting from a flashlight or lamp held at mattress level shows sag much more clearly than overhead room lighting.
Step 6: Photograph the Foundation
Take photographs of the bed frame and foundation or box spring. Photograph the slat spacing with a ruler showing the gap between slats. Most mattress warranties require slat spacing of no more than 3 inches (some specify 2 to 2.5 inches). If your slat spacing exceeds the warranty requirement, document when you purchased the frame and whether the manufacturer's instructions specified slat spacing requirements at the time of purchase.
Step 7: Compile Your Documentation Package
Your claim package should include: original purchase receipt (showing date, model, and price), photographs from Steps 5 and 6, your measurement notes, and a written description of the problem. Contact the retailer where you purchased (not the manufacturer directly, in most cases) and ask for their warranty claim form and submission process.
Restonic Warranty: What the Rules Say
We carry Restonic mattresses at Mattress Miracle, and we know their warranty terms well. Here is what Restonic covers, in plain language:
Restonic Warranty Basics
- Coverage period: Varies by model. ComfortCare models carry a 10-year limited warranty. Revive series carries varying coverage.
- What is covered: Manufacturing defects including visible sagging that exceeds the indentation threshold, broken coil springs, and edge support failure not caused by misuse.
- Indentation threshold: Body impressions greater than 1.5 inches (38 mm) as measured without body weight are covered as a manufacturing defect.
- What voids the warranty: Use without a proper foundation, slat gaps exceeding manufacturer specifications, water damage, staining (which is why we always recommend mattress protectors from day one), physical abuse, burns, or removing the law tag.
- Remedy: Restonic warranties typically offer repair or replacement at the manufacturer's discretion. A pro-rated warranty means the replacement value decreases over time even when a defect exists.
The important detail about the law tag: that small tag on your mattress that says "Do Not Remove Under Penalty of Law" (the penalty applies to retailers, not consumers, but manufacturers sometimes use tag removal as grounds to deny a claim). Leave it attached for the life of the mattress.
When you buy a mattress from us, Brad or Dorothy will always explain the warranty terms in plain language before you leave the showroom. We would rather you understand the coverage upfront than be surprised when you need it.
Does Your Bed Frame Affect Your Warranty?
Yes, significantly. Foundation and frame requirements are among the most commonly cited reasons for warranty claim denial.
The 3-Inch Slat Gap Question
Most mattress manufacturers specify maximum slat spacing in their warranty terms. The common specification is slats no more than 3 inches apart, with a centre support if the frame is queen size or larger. Some manufacturers specify 2.5 inches or even 2 inches for foam and hybrid mattresses. If your slat spacing exceeds the specified maximum, the manufacturer can argue that the foundation contributed to the premature indentation and deny the claim. Measure your slat gaps as part of your documentation, even if they meet the requirement. Showing compliance proactively strengthens your position.
Foundation Requirements That Affect Warranty Validity
- Slat spacing: No more than 2.5-3 inches (varies by manufacturer and mattress type). Use a ruler to measure between slats from edge to edge.
- Centre support beam: Required for queen and king frames. Without it, the frame can bow in the middle, causing sag that is attributed to the frame rather than the mattress.
- Box spring condition: If using a box spring, it must be in good condition (no broken springs or sagging), the correct size, and rated for the mattress. A broken box spring can void a mattress warranty.
- Platform bed compatibility: Solid platform surfaces are generally fine. Slatted platforms need to meet slat spacing requirements. Avoid metal platforms with wide gaps.
- Frame leg support: King and queen frames typically require a centre leg in addition to the four corner legs.
Documentation That Makes or Breaks a Claim
We have seen warranty claims succeed and fail based on documentation quality rather than the merits of the defect. A mattress with a genuine 2-inch sag can be denied if the customer cannot produce the original receipt. A marginal 1.5-inch sag can be approved when the customer submits clear photographs, a detailed timeline, and all the right paperwork.
Keep These From Day One
The moment you buy a mattress, photograph it, photograph the receipt, and store both somewhere you will find them in 5-8 years. Email the photos to yourself so they are date-stamped and cloud-stored. Take a photo of the mattress label (with the model number and serial number). This 10-minute task at purchase is worth more than any warranty extension you could buy.
When submitting a claim, your documentation package should include:
- Original receipt or invoice showing model name, price, purchase date, and retailer
- Mattress label photograph (model number, serial number)
- Photographs of the sag with straight edge and ruler visible
- Photographs of the foundation showing slat spacing
- A written timeline of when the problem started and how it progressed
- Any previous communications with the retailer or manufacturer about the issue
Submit through the retailer first. Most manufacturers require warranty claims to go through the point of purchase. If you purchased at Mattress Miracle, call us at (519) 770-0001 and we will walk you through the process and assist with the submission on your behalf.
Under Ontario's Consumer Protection Act, you also have rights independent of the manufacturer's warranty. If a mattress fails to perform as reasonably expected within a reasonable period, you may have recourse through consumer protection legislation even if the manufacturer's warranty has limitations. For significant claims, consulting with a consumer rights advocate or the Ministry of Government and Consumer Services is worth considering.
Frequently Asked Questions
What is the minimum sag measurement for a mattress warranty claim in Canada?
Most Canadian mattress manufacturers set their warranty indentation threshold at 1.5 inches (approximately 38 mm) measured without body weight, using a rigid straight edge. Some premium manufacturers use 1 inch; some budget warranties use 2 inches. The threshold is specified in your warranty documentation. Measure at the deepest point of the sag, not an average across the surface.
Does a 3-inch slat gap void my Restonic mattress warranty?
It depends on the specific Restonic model and warranty terms. Restonic, like most manufacturers, specifies a maximum slat spacing in their warranty conditions. If your slats exceed that specification, the manufacturer can use this as grounds to deny a claim. Measure your slat gaps before submitting a claim and document that they meet the requirement if they do. If they don't meet the specification, address the frame issue and see whether the manufacturer is willing to assess the mattress defect independently of the foundation problem.
Can I remove the law tag from my mattress?
The "Do Not Remove" warning on the mattress tag is directed at retailers, not consumers. You can legally remove it. However, some manufacturers cite tag removal as a basis to deny warranty claims. Our advice is to leave it attached. It costs you nothing and can prevent a claim dispute.
My mattress feels softer than when I bought it. Is that covered?
Foam softening (IFD decay) is a normal material change that is not covered as a manufacturing defect by most warranties. What is covered is visible indentation that exceeds the threshold measurement. A mattress can feel noticeably softer without showing enough measurable indentation to meet the warranty threshold. This is the most common source of customer frustration with mattress warranties.
How does Mattress Miracle help with warranty claims?
If you purchased your mattress at our Brantford showroom at 441 1/2 West Street, we will assist with the warranty claim process. Call Brad at (519) 770-0001, describe the issue, and we will advise on the measurement process and help submit the claim to the manufacturer on your behalf. We have been doing this for over 35 years and know how to present a claim effectively.
Sources
- Consumers Council of Canada. (2023). Consumer Rights and Mattress Warranties. consumercouncil.com.
- International Sleep Products Association (ISPA). (2024). Mattress Warranty Standards and Industry Practices. sleepproducts.org.
- Ontario. (2002). Consumer Protection Act, 2002, SO 2002, c 30, Sch A. ontario.ca/laws/statute/02c30
- Defloor, T. (2000). The effect of position and mattress on interface pressure. Applied Nursing Research, 13(1), 2–11. (foundational research on mattress pressure and deformation)
- Jacobson, B.H., Boolani, A., and Smith, D.B. (2009). Changes in back pain, sleep quality, and perceived stress after introduction of new bedding systems. Journal of Chiropractic Medicine, 8(1), 1–8. doi.org/10.1016/j.jcm.2008.09.002
- Dunlop, M., et al. (2020). Foam indentation force deflection and its relationship to long-term mattress performance. Journal of Materials Science. (IFD decay reference)
Visit Our Brantford Showroom
Mattress Miracle
441 1/2 West Street, Brantford
Phone: (519) 770-0001
Hours: Mon-Wed 10-6, Thu-Fri 10-7, Sat 10-5, Sun 12-4
Dealing with a sagging mattress and not sure whether it qualifies for a warranty claim? Call Brad before you do anything else. We can advise on the measurement process and, if the mattress was purchased here, help you navigate the claim.
Related Reading
- Mattress Warranty and Sagging Guide Canada: What You Need to Know
- Why Mattress Foam Goes Soft: Understanding IFD Decay
- Coil Gauge In-Store Buyer's Checklist
- Why Does Mattress Foam Turn Yellow? Polyfoam Oxidation Explained
- How to Remove Urine from a Memory Foam Mattress
- Mattress Cleaning Brantford: Services and DIY Guide
- Removable Mattress Covers: What to Ask Before You Buy
- Best Mattress for Night Shift Workers: Sleep Guide