Exterior Foam Coat #026

Exterior Foam Coat #026
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SKU: #026-3
Weight: 3.40 lbs
Fortifier/additive: Not an additive
Feel: Strong/hard
Application time: 3-40 Minutes
Work time: 1-3 hours
Cure time: Sets up in hours but takes 5 days to reach full strength
Weatherproof: Weather Resistant
Sandable: Sandable only before completely set
Paint/Stain: Can be stained or painted
Compatible with: Boost; Mesh; Acrylic Paint; Stain

Select Size:

Rock hard finish for all of your outdoor (and indoor) foam projects. This stuff is super tough. It is not sandable. Has a rough stone feel when dry. It can be troweled smooth, or brushed to make a super rough finish.

-Adheres to polystyrene foams.
-Forms a weather resistant surface.
-Easy to mix. Just add water.
-Use above or below grade
-Apply with paintbrush or trowel.
-Many decorative surface textures can be created.
-Soap and water clean-up.
-Add Boost fortifier if extra strength is desired. (will not work with Bounce)

MIXING: Settling may occur in shipping causing a gritty texture that does not stick well. Remix if there is separation in dry mixture. Use when temperatures are between 40°F (4°C) and 100°F (38°C). Mix in a clean container with clean water. Add about 3 parts powder to 1 part water and mix until Foam Coat turns to a smooth paste. A drier mix is stronger. Do not overmix.
APPLYING: If using extruded foam (ie Blueboard or Pinkboard) roughen surface with coarse sandpaper. Fill big cracks and holes by applying pasty mixture with a trowel. You may add more water until mixture is thin enough to apply with a paint brush, although thinning weakens coating. Can be applied with a standard spray hopper. Use thinned mixture to texture large areas. For best strength apply at least 1/4" (6mm) thick. Multiple coats may be applied. Try texturing surface before coating sets.
SET TIME: Use within 30 minutes. Sets up in 1-3 hours.  Fogging the surface for 24 hours will increase strength. 
FINISHING: Remove dust before painting. This product goes on rough and is not sandable. Finish as the surface is setting up.
CLEAN-UP: Clean tools and brushes with clean soapy water before coating hardens.

WARNING: Avoid prolonged contact with skin. Wear dust, skin and eye protection. Use approved respirator when sanding. In case of eye contact, flush immediately with water, consult a physician. Wash hands with soap and water after use and before eating. Keep out of reach of children.

1/64” thick 36 sq ft
1/16” thick 9 sq ft
1/4" thick 2.25 sq ft

  • Bulk 25 lbs Foam Coat ships in a separate box from anything else that you order, so the shipping charges may be more than what you see calculated.
  • If the FedEx Shipping charges for the 25 lbs of Foam Coat alone come out to more than $14, then make a note in the "notes" box at the end of the order form saying that you prefer we ship by USPS Priority Mail (2-3 day delivery) in a Medium Flat Rate Box for $14.30. An order of 50 lbs of Foam Coat will fit in a USPS Priority Mail Large Flat Rate Box for $18.80
  • Discount rates are available for large quantities. Pallets can ship for as low as $150 to most commercial locations in the continental US. Call or email us for details. 866.735.9255

1/64” thick 288 sq ft
1/16” thick 72 sq ft
1/4” thick 18 sq ft

1   Day   750 psi
7   Day   2500 psi
28 Day  3500 psi

1   Day   350 psi
7   Day   550 psi
28 Day  1250 psi

Flammability: Noncombustible and not explosive.
Auto-ignition Temperature: Not Applicable
Flash Points: Not Applicable

Click here for Foam Coat System Mixing Details and User Tips

Click here for Foam Coating and Gluing FAQs

Made in USA.

WARRANTY: HWFF Inc./dba Hot Wire Foam Factory warrants this product to be of merchantable quality when used or applied in accordance with the instructions herein. The product is not warranted as suitable for any purpose or use other than the general purpose for which it is intended. Liability under this warranty is limited to the replacement of its product (as purchased) found to be defective, or at the shipping companies’ option, to refund the purchase price. In the event of a claim under this warranty, notice must be given to The Hot Wire Foam Factory in writing. This limited warranty is issued and accepted in lieu of all other express warranties and expressly excludes liability for consequential damages. MSDS available.


Hy HWFF We have a large project that we are making plans on covering it with your exterior foam coat . This will be to large of a project to apply foam coat by hand & we would like to spray it on ! I have read you can apply foam coat with a hopper, but can not find any information on how to mix & or apply it using a spray method ? Any info on this would help greatly Thanks Jerry

Hi Jerry, You are the second person to ask about this today. I've used a cheap under $100 hopper gun and tiny pancake compressor from Home Dopey and a $250 gun that has a built-in pressure meter/regulator and 6 built-in tips that ran off a $2,000 stationary Ingersol compressor. Didn't notice a big difference. Just get the mix to a pancake batter consistency and you should be fine. You will only need Boost for the first somewhat wet coat, and not a very thick coat, just enough to give the next layer something to stick to. The Exterior Foam Coat sticks really well to itself. Don't let foam coat with Boost dry in your or on any equipment. It does not come off with any known solvents and doesn't easily chip off. I've got a video almost finished showing someone mixing and spraying this with a hopper.

I want to re-coat 2 foam planters because the white finish is wearing off. Would this work for my project?

Yes, you can use our Exterior Foam Coat, but depending on what kind of foam the planters are made out of you might have to add Boost liquid fortifier. Foam Coat will stick well to polystyrene foam, the kind that has the little white bubbles, but not polyurethane which is smoother and harder and often yellowish. Boost will make the foam coat stick to almost any surface. You can first do a thin coat with Boost, then your subsequent coats without it. 

Hello, I am using two part expanding polyurethane foam to cast garden sculptures rather than cement. The purpose is so clients who cannot either move or host an 800 lb piece of work can still have one in their garden. Would you recommend the Exterior Foam Coat for this? I see the Boulder Image pictures in your gallery where they have done similar work and it appears to be holding up to lots of moisture and use. Any tips on getting it sticky enough for this type of foam or will mixing it with Boost be enough? The problem is that this foam is glossy and doesn't have much 'tooth'.

Hi Ron,

People who have been using the two part expanding polyurethane foams like Great Stuff can't get our coatings to stick. Probably because they are waterproof. Several customers have recently tried adding Boost to All Purpose and to Exterior Foam Coat with one reporting back that they adhered well. I can't vouch for this as I haven't tried it myself.

Note that subsequent layers should not need Boost. If you go thicker than 1/8" with Boost you could get some surface fissures. We have applied up to 1/2 thick layers of straight Exterior Foam Coat with no cracking.

One of the most difficult parts of coating foam is getting the first layer to leave the brush to go onto the foam, so yes, hopper-spraying at least the first coat on to give some 'tooth' to the next layer is a smart technique. Pancake batter thickness seems to work well in our hopper gun.

We, and many of our customers, have made boulders out of EPS foam, but each needs to be carved.

If you would like to send some scraps of this foam to us we will do some testing:
Hot Wire Foam Factory
Product Testing/Dave
216 East Laurel Ave
Lompoc, CA 93436

How long do I need to wait between layers of all purpose foam coat and a second layer of foam coat or paint, and how much longer would the drying time be for the exterior foam coat? Thank you for using our shopping system

Hi Patricia,

You can apply subsequent layers up to 3/8" thick of All Purpose Foam Coat in about one hour increments. For painting, wait until the last coating no longer feels cold to the touch and when it loses its darker/wet look, usually in 2-3 hours.

The Exterior Foam Coat applied in1/8" to 1/4" thick layers will be dry enough for subsequent layers in 6-12 hours, depending on how hot and dry the atmosphere is. You can apply subsequent layers as soon as it sets up, usually in 1-2 hours, but applying this soon will increase the overall drying time. For painting, follow the same instructions as for the All Purpose, but it will be quite a bit longer, probably 6-12 hours.

Note that if you apply either foam coat with a hopper gun you can keep applying thin layer after thin layer until it starts slumping (see the video on our YouTube Channel: Exterior Foam Coat Applied With Hopper Gun. It will dry much faster when applied with a hopper gun.

It's always a good idea to play around with some small batches until you find the procedure that best suits your needs. Victoria, who teaches foam coating, tells her students that once they've made a couple of batches it will feel simpler than cooking a batch of pre-mixed cookies.

Let us know if you have any further questions,

I am using polystyrene foam to create a slate look background like this one on YouTube-

He is using All Purpose Foam Coat in his video. It is easier to apply and dries faster than the Exterior Foam Coat, but the Exterior is stronger and looks and feels more like real stone than the All Purpose and will have enough texture for your lizard to climb on.

Thinning down a lot will weaken both of the coatings. It's better to exaggerate your details an put it on thicker. You can create a lot of your detail in the foam coat as it dries. Check out the Foam Gone Wild DVD.

We have a foam-coat/stain system that is aquarium safe and will produce a beautiful natural stone or reef look. Exterior Foam Coat is applied over the foam shape. The coating is then sealed with Stainfast, which is also a base for water-base stains. Stainfast does not have NSF approval because it is not a coating. It seals on a molecular level. It is a densifier which prevents water from passing through after the chemical conversion. Stainfast was used to seal sea life exhibits at Sea World in San Diego.

Lots more information on using Foam Coat in aquariums and reptile enclosures here:
And examples with images here:

Lots of good options!

How durable would Exterior Foam Coat be outside with wind and rain snow direct sun and wide temperature changes from +90 to -40? I plan on using the Pink foam board 4x8 sheets and carving my own Stone Faux Pannels to future on the bottom of my porch and house, we have a lot of wind rain and snow and hot sun and sub zero temperature.

The Exterior Foam Coat is made to hold up in all weather conditions. It will easily withstand the hottest climate conditions, and although low temperatures will not damage Exterior Foam Coat a combination of moisture and freezing temperatures can. Our product is similar, though stronger and stays adhered to foam much better than stucco, but will react the same to extreme weather conditions. Here is an article that will give you some good parameters for your project:
Exterior Foam Coat is denser and less permeable than stucco, so should work somewhat better in moist freezing conditions than stucco does. Do any homes in your area have stucco finishes? Have you noticed a breakdown of the stucco where it is not sealed with paint?

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3 Most useful customer reviews
Scott Aldrich
Feb 22, 2017
This customer purchased the item at our site.
I build Vivarium Hardscapes and use this product to provide a rock like feel and appearance, it also provides much needed strength.
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Tina Padziora
Dec 31, 2016
This customer purchased the item at our site.
OMG. No more plaster use for my projects!! This exterior foam coat is awesome. I tested it by applying it to my styrofoam then blasted it with a high pressure water hose (apx 20 feet from target) then for kicks I took a sand blaster (apx 30 feet from target) to it so I could see what weather would do. Not 1 dent, scrape, or puncture anywhere. This stuff dries really fast and is really hard as rock when dry. If you want a product that will give you a stable long lasting finished project this is what you need. And NO I do not work for this company. But I will be buying stock if it is available!
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Bobby Harpoon
Nov 26, 2016
This customer purchased the item at our site.
This is a great product for increasing the streangth of the surface of your prodcts. I was amazed by how tough it dried. There are vidieos on how to create texture on the outer surfaces with this product. The one draw back that I have found. Is clearly stated in their own product descrption. "This product goes on rough and is not sandable. Finish as the surface is setting up." When I left some high ridges or spikes where the adhesion properties made it create a high draw point when lifting the application tool. It was very difficult to remove when dried. Best to make the finish as needed while applying product. It does make the surface tough which is the high light to this product.
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