CeraZorb® Insulating Synthetic Cork Underlayment (4' x 4') - 25 Sheets / 400 sq.ft

CeraZorb® Insulating Synthetic Cork Underlayment (4' x 4') - 25 Sheets / 400 sq.ft

$1,100.00 19 Reviews

  • Heat and cold resistant, and will not rot, support mold and mildew, or absorb moisture.
  • Stable and durable, remaining unchanged after repeated impact loads.
  • CeraZorb® has a 1.5 R-value, and it offers crack isolation of up to ¼”.
  • Lightweight, up to 25 times lighter than 1/4” backer board, and weighs in at only 28 lbs. per each 400 sq. ft. box.
  • Can be set under tile and stone, over any acceptable sub floor.

CeraZorb Underlayment Description

CeraZorb is a synthetic cork underlayment that is installed on top of a subfloor and below a heating element. It is recommended when installing an electric floor heating system over a concrete slab to prevent heat loss. By creating a thermal break, the heat is prevented from sinking into the concrete, and more heat radiates into the floor covering and room. In addition to preventing unnecessary heat loss, CeraZorb provides sound dampening benefits and double the crack isolation benefits when compared to cork.

CeraZorb is lightweight—up to 25 times lighter than traditional 1/4" backer board. It is available in 2’ x 4’ and 4’ x 4’ sheets, and in packs of up to 100. CeraZorb is a 5 mm. (roughly 3/16 in.) thick, synthetic cork underlayment system that is specifically designed for setting tile and stone and is an excellent insulation choice under our TempZone™ electric radiant floor-heating product. It’s a very resilient underlayment with compressive strength of 34 psi at 10% deformation. 

Twenty-five 4’ x 4’ sheets provides 400 sq. ft. of coverage and is great for medium sized projects. Typically ships in 1 box.


Insulation Specification

Acoustic testing on 6" slab, no ceiling IIC 52 wood construction. FIIC 59 - 7.5" concrete slab. ΔIIC 20 - 6" concrete slab
Compressive Strength 34 psi @ 10% Deformation
R-value 1.5

Product Dimensions

Coverage 400 Sq. Ft.
Length 4′
Thickness 0.187″
Weight 27.5 lbs
Width 4′


UPC (GTIN-12) 881308056308

Warranty / Certifications

TCNA Robinson test Light Commercial
Warranty 5 years

Customer Questions & Answers

Is a floor heating underlayment always required?

No, an underlayment isn’t always necessary. 

However, there are some situations in which the use of an underlayment would be required, such as heating over a cement slab (where an insulating underlayment would most likely be required).

How do I figure out how much underlayment I’ll need for my floor heating project?

The best way is to use our Radiant Floor Heating Quote Builder tool. It’s a great way to get an estimation by simply providing project information like room size and subfloor type. 

Which floor heating underlayment is best for a high-moisture installation like a bathroom?

Typically, an uncoupling membrane like Prodeso will be best for this application because it can be paired with accessories to effectively waterproof the subfloor. 

However, if you have a cement subfloor, then CeraZorb synthetic cork is a good choice because of its high R-value and moisture resistance. 

How are insulating underlayments different from uncoupling membranes?

Insulating underlayments and uncoupling membranes share some key characteristics like providing crack isolation benefits. But they are separated by their primary functions. 

Insulating underlayments, like cork or CeraZorb, provide a thermal break between a subfloor and the heating elements, which can help prevent “heat sink” and increase energy efficiency. This can be particularly beneficial if you are trying to heat a room above a cement slab or above an unheated garage. 
Uncoupling membranes, like the Prodeso membrane, are great for protecting relatively fragile floor coverings like tile from foundational movement. They also allow for faster installation times than many other types of floor heating. 

Customer Reviews

CeraZorb Underlayment achieved an average rating of 4.9 stars with 19 reviews by our customers.

Just enough insulation from slab.

Kelly C., Biloxi, MS on 02/25/2019

Product minimizes heat loss from concrete slab on cold days. Product was grouted down first and then the element rolled out. Great at minimizing thickness of completed floor!

Liliana, Eldon, MO on 02/17/2019

Works surprisingly well

Andrea B., Brattleboro, VT on 02/01/2019

I'll admit, when this arrived I was doubtful that it would do anything - it's pretty thin. But halfway through the CeraZorb underlayment installation on the basement floor, we could feel it working - definitely blocked the chill coming through the concrete! I'm certain this will keep the radiant floor heating in the room where it belongs, and not seeping down into the concrete below.

Daniel R., Nogales, AZ on 01/30/2019

Ron L., Albert Lea, MN on 08/13/2017

Great product

CNR G., PASSAIC, NJ on 05/14/2017

Great product, fast shipping

Great product

Tim O., BELLEVILLE, IL on 02/03/2017

Great product, would highly recommend if you are putting a heated floor over a concrete basement floor. They are pricey though if you need a lot.

Great Protection and Resistance

Mike T., Fishers, IN on 01/08/2017

This product was easy to install and added great protection and resistance between the slab an the heated floor.

I will be using this system on all future jobs

Bruce A., WOODCLIFF LAKE, NJ on 11/03/2016

Great product with exceptional customer service. I will be using this system on all future jobs.

Very impressed

Graeme H., EDMONTON, AB on 09/07/2016

Very impressed with the insulation value of these tiles especially for being only 5 mm thick.

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