a 9 inch flat foundation — 9 Inch Foundation

Engineered to support your Stearns and Foster^® mattress with a perfectly solid, flat surface.

Profile

High - 9"
Low - 5"

Size

$315.00

Qty

Free Delivery — Arrives in 2-3 Weeks

Designed in the USA
^{Crafted with care and to last}

Fashion
+ Function

The perfect mattress isn't complete without the perfect foundation. Our flat foundations are designed to take the place of a traditional box spring and can be placed directly on your existing bed frame.

Fashion

Name: Flat Foundation 9" - Twin Long
Brand: Stearns & Foster
SKU: 748369625235
Price: 240.00 USD
Availability: InStock
Rating: 4.7368421052631575 (133 reviews)

+ Function

CRAFTED TO

Complement

Constructed with the finest textiles, our Stearns & Foster^® foundation is designed to enhance the look and feel of your mattress.

Why You'll Love It

Perfect Match

Our solid surface foundation is crafted to provide years of stationary support. Designed and upholstered to complement our mattresses and your bedroom décor.

Why You'll Love It

SF Lux Hybrid Mattress on a foundation Mobile

Perfect Match

Our solid surface foundation is crafted to provide years of stationary support. Designed and upholstered to complement our mattresses and your bedroom décor.

An image showing the difference in height between the 5 and 9 inch foundations

Custom Comfort

Our foundations are available in a 9” height that matches a traditional box spring and a lower 5” profile for a more modern look that will easily fit through more narrow stairways.

Custom Comfort

Our foundations are available in a 9” height that matches a traditional box spring and a lower 5” profile for a more modern look that will easily fit through more narrow stairways.

Crafted

For you

Constructed with the finest textiles that enhance the look and feel of your mattress, our Stearns & Foster^® Foundation is designed to complement your style.

Product Specifications

Size Availability

Twin: 74L" x 38W"

Twin Long: 79L" x 38W"

Full: 74L" x 53W"

Queen: 79L" x 60W"

Split Queen: 79L" x 30W" (each piece/ 2-piece foundation)

King/Split: 79L" x 38W" (each piece/ 2-piece foundation)

CA King/Split: 83L" x 36W" (each piece/ 2-piece foundation)

Product Weight

High Profile 9"

Twin: 31 lbs.
Twin Long: 35 lbs.
Full: 42 lbs.
Queen: 48 lbs.
Split Queen: 60 lbs. (30 lbs each piece)
King/Split: 70 lbs. (35 lbs each piece)
CA King/Split: 70 lbs. (35 lbs each piece)

Low Profile 5"

Twin: 25 lbs.
Twin Long: 29 lbs.
Full: 38 lbs.
Queen: 46 lbs.
Split Queen: 58 lbs. (29 lbs each piece)
King/Split: 58 lbs. (29 lbs each piece)
CA King/Split: 56 lbs. (28 lbs each piece)

Warranty & Returns

Warranty

Your Stearns & Foster foundation is covered under a 10-Year Limited Warranty.

View warranty details.

Return Policy

This product cannot be returned and the 90-Night Trial does not apply.

Care Instructions:

We made caring for your foundation straightforward and easy.

Read our product care instructions.

Sort by:

Rated 5 out of 5 stars

Flat Foundation

Aug 11, 2026

Source:

Stearns & Foster

Sweepstakes

Bill, Bolivia NC

The foundation works like it’s supposed to..quietly and out of sight.

Rated 5 out of 5 stars

Flat Foundation

Jul 6, 2026

Source:

Stearns & Foster

Sweepstakes

Mike, Las Vegas NV

The Reserve mattress is very comfy and luxurious. The flat foundation I was disappointed with. It’s not a true flat foundation.

Rated 5 out of 5 stars

Flat Foundation

Jun 28, 2026

Source:

Stearns & Foster

Sweepstakes

Hapy Sleeper, Maryland

This unsung hero is the perfect match for our brand new Stearns and foster mattress! It’s just the right height, well-made, and quality construction.

Rated 5 out of 5 stars

Flat Foundation

Jun 21, 2026

Source:

Stearns & Foster

Sweepstakes

S.G., Scottsdale, Arizona

Hello, I received the Sterns and Foster tight top estate mattress, which was my mistake. I then contacted Stern and Foster support and change to the Stearns and Foster pillow top queen mattress. As we speak, The pillow top queen mattress is in production and will be shipped out as soon as possible. I am anxiously awaiting this new Sterns and Foster pillow top queen mattress, as we already have a king size pillow top mattress. I can’t tell you how excited I am to have an additional queen size estate pillow top, which will be in an additional bedroom. I would not even think about purchasing a mattress from another company as Sterns and Foster is quite the best. Thanks again SG

Rated 5 out of 5 stars

Flat Foundation

Jun 8, 2026

Source:

Stearns & Foster

Sweepstakes

Great Foundation , Salem

This 9” Stearns & Foster Flat Foundation is the perfect height to give our new mattress a lift. It fits perfectly in our Queen bed frame. It is well made. Highly recommend this item.

Rated 5 out of 5 stars

Flat Foundation

Apr 1, 2026

Source:

Stearns & Foster

Sweepstakes

Robin, South Lyon, MI

We were looking for the firm mattress we purchased for another home two years ago when my back started aching. All research shows if your spine is old and not in the best shape, the firmer the better. Alas, the mattress was not available in any store anymore, so we called Sterns and Foster directly and were told "sure, we can make that mattress again for you". We were thrilled and within just 2 days my back was feeling much better. This was such a blessing, as I just started drug therapy for my cancer and felt the care, concern and urgency to get this to us quickly was genuine and heartfelt. I hope the "paying forward" that was done by your salesperson and company comes back to you tenfold. Thank you!!!!

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Flat Foundation

Limited Time

Free Flat Foundation (Up to $315 Value)

Fashion
+ Function

Fashion