Skip to content
Free Shipping On All Orders
Free Shipping On All Orders
Delta FL – Dimpled Membrane for Slab-On-Grade Floors – 3’6” x 30’

Delta FL – Dimpled Membrane for Slab-On-Grade Floors – 3’6” x 30’

$216.86


FREE SHIPPING
SKU DFL-3.6x30

DELTA®-FL is a heavy-duty, dimpled plastic membrane designed to protect concrete and slab-on-grade floors from moisture, making basements dry, comfortable, and livable. It acts as both a capillary break and vapor barrier, preventing moisture from migrating through the concrete and damaging flooring materials.

The unique dimpled structure creates an air gap that equalizes water vapor pressure above and below the slab, stopping moisture from entering the basement space. This not only keeps floors dry but also provides a thermal break, making the floor feel warmer and increasing overall comfort.

With DELTA®-FL, sensitive flooring materials remain protected, and your basement becomes a more functional, inviting living area. It’s an effective, long-term solution to moisture issues, ensuring a dry and comfortable space.

Roll Size: 3'6 x 30' (105 Sq Ft)

Product Info

  • Model: Delta FL
  • Material: Special virgin high-density polyethylene stabilized (oxidation & UV)
  • Data Sheet: Download >
  • Installation Instructions: Download >
  • 3 Part Spec Sheet: Download >
  • Brochure: Download >
  • Free Shipping
  • Need a written quote? Request Online
  • Questions?  Call (800) 731-8420

Product Benefits

  • Provides a reliable capillary break and vapor barrier, ensuring a dry, livable basement
  • Creates a thermal break, making basement floor feel warmer
  • Impact-resistant HDPE makes the product extremely tough and rugged
  • Outstanding compressive strength of >4500 lb/sf
  • Minimal reduction in head room (8 mm)
  • Installed dimple side down, a ventilated air space is created above the slab, allowing equalization of water vapor pressure
  • Seams are simply taped with DELTA®-MOISTURE PROOF TAPE to ensure that moisture cannot migrate inwards through the joint areas
  • The lightweight product comes in two different roll sizes. It is fast and easy enough for the average homeowner to install
  • DELTA®-FL topped with plywood sheets will allow a variety of floor coverings to be installed: carpeting with underlay, vinyl flooring, hardwood flooring
  • Laminate floors can be directly laid on top of the membrane

SHIPPING TIME

  • All Delta rolls ship for free (standard ground, see map)
  • Call: (800) 731-8420 for pricing and shipping questions.

    Shipping estimates shown on the map pertain to this specific product only. Orders typically ship within 5 business days if the order is placed before 12:00 noon EST. Transit times displayed in the map are listed in business days, and are approximate.  The day that the order is shipped is not counted as a transit day.

    map_0154_JUL24.jpg__PID:580f1856-8cbb-4d73-bcab-b7de26ed3a49

    Other Delta Products:

    Delta Adhesive for Cold Weather Applications - 4.5 Gallons
    Delta Adhesive for Cold Weather Applications - 4.5 Gallons

    Delta Adhesive for Cold Weather Applications - 4.5 Gallons

    $576.91
    Delta Bug Screen - Bag of 5' Strips (20 Units)
    Delta Bug Screen - Bag of 5' Strips (20 Units)

    Delta Bug Screen - Bag of 5' Strips (20 Units)

    $219.15
    Delta Drain 2000 HI-X
    Delta Drain 2000 HI-X - 4' x 50'
    Delta Drain 2000 HI-X - 4' x 50'
    Delta Drain 2000 HI-X - 4' x 50'
    Delta Drain 2000 HI-X
    Delta Drain 2000 HI-X - 4' x 50'
    Delta Drain 2000 HI-X - 4' x 50'
    Delta Drain 2000 HI-X - 4' x 50'

    Delta Drain 2000 HI-X - 4' x 50'

    $301.22
    Delta Drain 2000 HI-X
    Delta Drain 2000 HI-X - 6' x 50'
    Delta Drain 2000 HI-X - 6' x 50'
    Delta Drain 2000 HI-X - 6' x 50'
    Delta Drain 2000 HI-X
    Delta Drain 2000 HI-X - 6' x 50'
    Delta Drain 2000 HI-X - 6' x 50'
    Delta Drain 2000 HI-X - 6' x 50'

    Delta Drain 2000 HI-X - 6' x 50'

    $516.41
    Delta Drain 6000 HI-X
    Delta Drain 6000 HI-X - 4' x 50'
    Delta Drain 6000 HI-X - 4' x 50'
    Delta Drain 6000 HI-X - 4' x 50'
    Delta Drain 6000 HI-X
    Delta Drain 6000 HI-X - 4' x 50'
    Delta Drain 6000 HI-X - 4' x 50'
    Delta Drain 6000 HI-X - 4' x 50'

    Delta Drain 6000 HI-X - 4' x 50'

    $313.00
    Delta Drain 6000 HI-X
    Delta Drain 6000 HI-X - 6' x 50'
    Delta Drain 6000 HI-X - 6' x 50'
    Delta Drain 6000 HI-X - 6' x 50'
    Delta Drain 6000 HI-X
    Delta Drain 6000 HI-X - 6' x 50'
    Delta Drain 6000 HI-X - 6' x 50'
    Delta Drain 6000 HI-X - 6' x 50'

    Delta Drain 6000 HI-X - 6' x 50'

    $534.08
    Delta Drain 6200 HI-X
    Delta Drain 6200 HI-X - 4' x 50'
    Delta Drain 6200 HI-X - 4' x 50'
    Delta Drain 6200 HI-X - 4' x 50'
    Delta Drain 6200 HI-X
    Delta Drain 6200 HI-X - 4' x 50'
    Delta Drain 6200 HI-X - 4' x 50'
    Delta Drain 6200 HI-X - 4' x 50'

    Delta Drain 6200 HI-X - 4' x 50'

    $326.33
    Delta Drain 6200 HI-X
    Delta Drain 6200 HI-X - 6' x 50'
    Delta Drain 6200 HI-X - 6' x 50'
    Delta Drain 6200 HI-X - 6' x 50'
    Delta Drain 6200 HI-X
    Delta Drain 6200 HI-X - 6' x 50'
    Delta Drain 6200 HI-X - 6' x 50'
    Delta Drain 6200 HI-X - 6' x 50'

    Delta Drain 6200 HI-X - 6' x 50'

    $554.07
    Delta Drain 9000 HI-X
    Delta Drain 9000 HI-X

    Delta Drain 9000 HI-X

    $632.66
    Delta Drain Drainage Composite
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7
    Delta Drain Drainage Composite - 6' x 65'7

    Delta Drain Drainage Composite - 6' x 65'7"

    $1,077.31
    Delta Drain Drainage Composite
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7
    Delta Drain Drainage Composite - 8' x 65'7

    Delta Drain Drainage Composite - 8' x 65'7"

    $667.09
    Delta Drain Grip Fastener
    Delta Drain Grip Fastener

    Delta Drain Grip Fastener

    $151.51
    Delta Drain Mold Strip
    Delta Drain Mold Strip

    Delta Drain Mold Strip

    $133.50
    Delta Drain Screw Fastener
    Delta Drain Screw Fastener

    Delta Drain Screw Fastener

    $67.35
    Delta Dry & Lath – Rainscreen & Fiberglass Lath – 3.3’ x 46’
    Delta Dry & Lath – Rainscreen & Fiberglass Lath – 3.3’ x 46’
    Delta Dry & Lath – Rainscreen & Fiberglass Lath – 3.3’ x 46’
    Delta Dry & Lath – Rainscreen & Fiberglass Lath – 3.3’ x 46’

    Delta Dry & Lath – Rainscreen & Fiberglass Lath – 3.3’ x 46’

    $425.51
    Delta Dry Stucco & Stone – 2 in 1 Ventilated Rainscreen – 3.3’ x 46’
    Delta Dry Stucco & Stone – 2 in 1 Ventilated Rainscreen – 3.3’ x 46’

    Delta Dry Stucco & Stone – 2 in 1 Ventilated Rainscreen – 3.3’ x 46’

    $312.53
    Delta Dry – Ventilated Rainscreen – 3.3’ x 50’
    Delta Dry – Ventilated Rainscreen – 3.3’ x 50’
    Delta Dry – Ventilated Rainscreen – 3.3’ x 50’
    Delta Dry – Ventilated Rainscreen – 3.3’ x 50’

    Delta Dry – Ventilated Rainscreen – 3.3’ x 50’

    $287.68
    Delta FL Moisture Proof Tape - 2.5
    Delta FL Moisture Proof Tape - 2.5

    Delta FL Moisture Proof Tape - 2.5" x 108'

    $41.56
    Delta LFS - Liquid Flashing & Sealant - 10 FL Oz Tube
    Delta LFS - Liquid Flashing & Sealant - 10 FL Oz Tube

    Delta LFS - Liquid Flashing & Sealant - 10 FL Oz Tube

    $24.41
    Delta MS Flash - 2
    Delta MS Flash - 2

    Delta MS Flash - 2" x 6' - 33 Strip Bundle

    $108.64
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane - 5' x 65.6'
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane - 5' x 65.6'

    Delta MS – Below Grade Dimpled Membrane - 5' x 65.6'

    $714.12
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane - 7' x 65.6'
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane
    Delta MS – Below Grade Dimpled Membrane - 7' x 65.6'

    Delta MS – Below Grade Dimpled Membrane - 7' x 65.6'

    $837.93
    Delta Multi-Band Tape for WRBs
    Delta Multi-Band Tape for WRBs

    Delta Multi-Band Tape for WRBs

    $72.14
    Delta Drain Sealant
    Delta Drain Sealant

    Delta Sealant

    $25.54
    Delta Drain T-FASTner
    Delta T-FASTner
    Delta T-FASTner
    Delta Drain T-FASTner
    Delta T-FASTner
    Delta T-FASTner

    Delta T-FASTner

    $28.43
    Delta Trela – Pitched Metal Roof Underlayment – 3’3” x 98’
    Delta Trela – Pitched Metal Roof Underlayment – 3’3” x 98’

    Delta Trela – Pitched Metal Roof Underlayment – 3’3” x 98’

    $676.31

    Delta® FL – Dimpled Membrane for Slab-On-Grade Floors: An Overview

    A moisture-protecting underlayment designed to keep basement and slab-on-grade floors warm, dry, and comfortable.

    Delta FL dimpled membrane diagram
    Cross-section of Delta® FL’s dimpled profile

    What is Delta® FL?

    Delta® FL is a dimpled membrane underlayment designed for use over concrete slabs, including basement and slab-on-grade floors. Made of high-density polyethylene (HDPE), it creates a reliable moisture barrier and a thermal break between the cold, damp concrete and finished flooring materials.

    Available in a convenient 3’6” x 30’ roll, Delta® FL is engineered to make basements and concrete slab floors warmer, drier, and more comfortable—while helping protect finished flooring from moisture damage.

    Delta FL being installed over concrete slab
    Easy installation directly over concrete slab

    How it works

    The unique dimpled profile of Delta® FL creates an air gap between the concrete and the finished flooring. This allows incidental moisture to move freely under the membrane and escape at the edges, instead of becoming trapped under flooring materials. The air gap also provides an insulating effect, reducing the cold feel of concrete floors.

    Key benefits

    • Moisture control: Stops ground moisture from seeping into finished floors.
    • Thermal break: Reduces heat loss through the slab, keeping floors warmer underfoot.
    • Durability: Made from tough HDPE that resists rot, mildew, and chemical degradation.
    • Comfort: Provides a smooth, solid base for finished flooring, improving comfort in living spaces.
    • Versatility: Compatible with laminate, engineered hardwood, carpet, and vinyl flooring.
    Delta FL underlayment during basement flooring project
    Delta® FL underlayment during a basement remodel

    Applications

    Delta® FL is ideal for:

    • Basement finishing projects
    • Slab-on-grade residential floors
    • Concrete garage conversions
    • Recreation rooms, workshops, and home offices

    Installation overview

    1. Ensure the concrete slab is clean, level, and free of debris.
    2. Unroll Delta® FL membrane with the dimples facing down.
    3. Cut to fit around walls and obstructions.
    4. Tightly butt side seams and tape joints with manufacturer-approved tape.
    5. Install finished flooring (laminate, carpet, engineered hardwood, etc.) directly over the membrane.

    Case study: Basement renovation

    Project: A homeowner in a cold-climate region wanted to finish their 1,000 sq. ft. basement into a family recreation room. Concerns included dampness, mold risk, and uncomfortably cold floors.

    Solution: Delta® FL was installed across the entire basement slab. Finished laminate flooring was then laid directly over the membrane without additional sleepers or plywood.

    Outcome: The finished basement had noticeably warmer, drier floors. Moisture testing after one season showed no elevated humidity under the flooring. The homeowner reported significant comfort improvements and peace of mind knowing their investment was protected.

    Frequently Asked Questions

    Can Delta® FL be used under carpet?
    Yes. Delta® FL provides a stable, dry base for carpet and padding in basement and slab-on-grade applications.
    Do I need plywood over Delta® FL?
    No. Finished flooring such as laminate, engineered hardwood, or carpet can be installed directly over Delta® FL.
    How thick is the membrane?
    Delta® FL is approximately 5/16" (8 mm) thick, creating an effective air gap between the slab and flooring.
    Is it resistant to mold?
    Yes. Made from HDPE, Delta® FL does not support mold growth and helps prevent moisture from reaching organic flooring materials.
    What roll size is available?
    The product is sold in 3’6” x 30’ rolls, covering approximately 108 square feet per roll.
    Get a Quote