Water Proof Carpet Underlay - Stage 2

Water Proof Carpet Underlay - 1.8sqm coverage
Water Proof Carpet Underlay - 1.8sqm coverage


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Car Builders Water Proof Carpet Underlay is a single layer, closed cell foam, meaning it does not hold water. It also works great as a thermal and acoustic insulation barrier.

It is suitable for 4x4's, convertibles and industrial vehicles, which get constantly exposed to wet environments.

Car Builders Water Proof Carpet Underlay will not stay damp, smell, rot or attract mould like pre-dated cotton mill scrap, traditionally used under carpets.

It comes with a peel and stick backing and is easy to cut and install. It is also effective as a thermal barrier to reduce heat transfer from the exterior of your vehicle.  The material will reduce radiant heat by up to 20°C, and can be the difference between discomfort and pleasure.



  • Light Weight
  • Easy installation - just peel off the release liner and adhere to surface.
  • Cuts with scissor and knife
  • Reduces heat transfer
  • Does not rot or deteriorate


  • Under carpets
  • Roof skins
  • Inside cavities
  • 1/4 panels
  • Doors
  • Firewalls


Each box comes with 1 sheet inside, each sheet is 1800mm x 950mm resulting in 1.71sq/m.



Waterproof Carpet Underlay FAQ

What thickness carpet underlay should I use?

Carpet underlay thicknesses range between 4-12mm. This range allows you to insulate effectively and fit it under tighter areas such as the transmission tunnel.





Sheet size:
1800 x 950mm 


Closed cell foam

Adhesive Resistance Temperature Range:
-40°C to +110°C (long term) +135°C (short term)

Flame retardant:
Yes, B2

Customer Reviews

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Waterproof underlay

By: on 13 June 2023
I'd tried conventional underlay for my custom floor (hot rod), which has some odd and complex curves in it. I decided to take the plunge with this product. Now I don't know why I ever doubted it. This stuff is great in my opinion. It is actually as good as the marketing suggests. Very easy to use, looks fantastic and forms well around curves (within reason obviously) sticking down really well. Very happy with this product.


Water proof carpet underlay

By: on 19 June 2022
Good quality product. Easy to install and cut to shape, and easy to read instructions on box.


Great product

By: on 8 March 2022
Waterproof underlay was light and very easy to install and cut as advertised and delivery came quicker than expected


Water Proof carpet underlay

By: on 29 September 2021
1st time user of this product and quite impressed, the sticky backing is strong and has stuck down well. I am on to the carpet next and I am confident that this underlay is going to provide a far superior finish than conventional woven underlay's.


Very pleased, great product

By: on 17 September 2021
Does exactly what it says. Two rolls was just right and it went down easily. Huge improvement to the noise and vibration. If I could cut straight it would have been even easier.



By: on 16 June 2021
Easy to mold to shape. Great looking carpet. Priced well.


Fantastic product

By: on 12 August 2020
Installed the waterproof underlay in my 4wd and am solidly impressed. Great quality product and super easy to install. Has made a huge reduction to interior sound levels from wind and road noise


So easy carpet underlay

By: on 3 August 2020
so easy to apply with the self adhesive backing. Just remember it doesn't stretch


Waterproof underlay

By: on 24 July 2020
Easy to install, makes the car interior very nice now.



By: on 3 May 2020
My install in not to turn my gq y60 td42 into an off roader 4x4 etc. It has had 25 years of that and I shipped it over from nz to keep the car I learnt to drive in going. This waterproof liner feels like luxury under the feet. I have both this, acoustic for speaker areas and heavy liner. This is my favorite of them so far. Difficult in the gq with all the euro modifications etc they offered and all the bolts etc. So lined cuts with the fabric tape then the aluminum tape. So far so good. Have added gaffer to some areas that I am still working on.



By: on 28 June 2019
great product ,easy to install and feels good to walk on