How to Spray Foam Insulation Yourself, Step by Step From the Kit Manuals

Step 1: Check the temperature of the space and the cans

The temperature of the work and the cans comes first, because every one of the five kit documents gives the same working window of 41 to 86 F. Four of them name 68 F as the best can temperature, and BEEST asks for 68 to 77 F. A colder job yields less foam and cures more slowly, as the FastCoat and ThermCoat sheets both say.

Bring the cans indoors the day before if the space is cold, and check the forecast for a garage, shed or crawl space that follows the weather. The spray foam weather check reads the outdoor conditions for your area, and the surface itself has to be inside the window as well as the air.

Step 2: Clean and lightly mist the surface

The surface has to be clean, dry and free of dust, oil and grease before it is sprayed, says the Stanley manual. The FastCoat, ThermCoat, Stanley and Sprayman manuals then ask for a light mist of water on the surface to improve adhesion and curing.

A light mist means a spray bottle, not a wet wall. Scrape off loose paint, old foam and dust on rim joists and masonry first, because foam bonds to what it touches and comes away with anything loose.

Step 3: Cover what stays clean, ventilate and suit up

Cured foam only comes off with a knife or a scraper, say the FastCoat, ThermCoat, Stanley and Sprayman manuals, so cover windows, wiring, floors and anything else that has to stay clean before the first can is opened. Uncured foam on skin, tools or surfaces comes off with the foam cleaner, if you catch it before it hardens.

Ventilate the space while you work: the SprayCoat and SuperCoat documents limit use to well-ventilated areas, and the Sprayman manual adds that fresh foam should not sit in a direct draft. Wear gloves, goggles, a mask and coveralls, as the FastCoat, ThermCoat and Sprayman manuals list them; the Stanley manual names the first three. BEEST is the one maker that names the respirator, a NIOSH respirator with organic vapor cartridges, and a paper dust mask is not that, so buy a cartridge respirator if your kit box only holds a mask.

Step 4: Shake the can and attach it to the gun

Shake each can for 20 to 30 seconds to mix the contents, then screw it onto the gun, the FastCoat, ThermCoat, Stanley and Sprayman manuals say. Hold the can upside down, with the gun below it, for the whole time you spray.

The gun has an adjustment knob or screw at the back that sets the output. Start low on a test board, then open it until the bead is even.

Step 5: Fit the right nozzle and hold the right distance

Nozzle A is for walls and other vertical surfaces and nozzle B for ceilings, on the FastCoat, SprayCoat, ThermCoat and SuperCoat documents alike; BEEST uses a blue tip for vertical work and a black one for horizontal. Hold the gun 12 to 18 inches from a wall. Under a ceiling, all five documents say 6 to 8 inches, and the FastCoat, ThermCoat, Sprayman and Stanley manuals hold the gun at about 45 degrees. One picture on the FastCoat sheet shows 12 to 16 inches, against 6 to 8 in its own text and manual.

Spray a wall from the bottom up in smooth, steady passes, the Sprayman manual says, and fill a vertical gap from the bottom to the top without overfilling it, because the foam keeps expanding as it cures.

Step 6: Spray the first layer, about 1 inch thick

Each of the five kits builds insulation in layers of about 1 inch, and none of them asks for a single thick pass. A slow, steady sweeping pace, as BEEST puts it, keeps the layer even, and stopping in one spot builds a lump you trim off later.

How thick the finished foam should be depends on the job and the climate zone, and the guide to spray foam thickness works it out from the target R-value. Most of the kit documents recommend at least 2 inches: the manuals build it as two layers of about 1 inch, and the FastCoat and ThermCoat data sheets ask for at least three layers to get there.

Step 7: Wait, mist again and spray the second layer

Wait about 30 minutes before the next layer on the FastCoat, ThermCoat, Sprayman and Stanley manuals, or 15 to 30 minutes on BEEST’s guide, and mist the first layer lightly with water before you spray over it. The FastCoat, ThermCoat and Stanley documents ask for the first layer to cure before the next goes on.

Step 8: Trim at 40 minutes and cover after 24 hours

The foam becomes trimmable after about 40 minutes, say the four coat kits, and you cut or shave the high spots with a knife or a spatula. Full cure takes 24 hours on the same four documents, and BEEST’s official page gives about 6 hours for FullStop against 24 in its own guide.

Cured foam that stays exposed to sunlight needs paint, plaster or another coating against UV, on the FastCoat, ThermCoat, Stanley and Sprayman documents. In a room people use, the foam belongs behind a thermal barrier such as half-inch gypsum board.

Step 9: Clean the gun, or park it for later

Clean the gun as soon as you finish with the foam cleaner made for it: take off the foam can, spray cleaner on the adapter and nozzle, screw on the cleaner can and pull the trigger until clear liquid comes out. If you are only taking a break, close the adjustment screw, spray a little cleaner on the nozzle tip and leave the can on the gun, upright with its base down.

Store cans upright in a cool, dry place between 41 and 77 F and never above 122 F, say the Stanley and Sprayman manuals. A can left upside down blocks its own valve.

How long the job takes

No maker publishes how long a spray foam job takes, so the time is the sum of the steps they do give. A 20 by 20 foot garage ceiling at 2 inches is 800 board feet, about 44 cans with a 10 percent allowance, sprayed as two layers. The waits the documents set are fixed:

• 30 minutes between the first and second layer, on the FastCoat, ThermCoat, Sprayman and Stanley manuals
• 40 minutes after the last layer before trimming
• 24 hours before the foam is covered, painted or closed in

Prep, masking and cleanup come on top of the spraying. Plan the spraying for one day and the covering for the next, and check the cure figures for your exact product in the spray foam cure times table, which sets every kit we track side by side.

What the five kit manuals say, side by side

The five ranked kits agree on the window, the layers and the cure, and differ on the ceiling distance, the wait between layers and the protective gear they name. Each cell is the document’s own figure; “not stated” means the documents we hold do not give one.

Step	FastCoat	SprayCoat	ThermCoat	SuperCoat	FullStop
Working temperature	41 to 86 F	41 to 86 F	41 to 86 F	41 to 86 F	41 to 86 F
Best can temperature	68 F	About 68 F	68 F	68 F	68 to 77 F
Shake	20 to 30 s (manual), 20 s (sheet)	20 to 30 s	20 to 30 s	20 to 30 s	Not stated
Distance from a wall	12 to 18 in	12 to 18 in	12 to 18 in	12 to 18 in	12 in
Distance under a ceiling	6 to 8 in (one sheet picture: 12 to 16 in)	6 to 8 in	6 to 8 in	6 to 8 in	6 to 8 in
Layer	1 in; 2 layers (manual), 3 or more to 2 in (sheet)	About 1 in	1 in; 2 layers (guide), 3 or more to 2 in (sheet)	About 1 in	About 1 in, 2 in total
Wait between layers	About 30 min	About 30 min	About 30 min	30 min	15 to 30 min
Mist with water	Before and between	Before and between	Before and between	Before and between	Not stated
Trim	40 min	About 40 min	40 min	40 min or less	After full cure
Full cure	24 h	24 h	24 h	24 h	24 h (guide), about 6 h (page)
Protective gear named	Gloves, goggles, mask, coveralls	Gloves, goggles, mask, coveralls	Gloves, goggles, mask, coveralls	Gloves, goggles, mask	Organic vapor respirator, glasses, coveralls, nitrile gloves

Questions before you start

The questions below come up before the first can is opened: the gear, the cover over the foam and the job itself.

What do you need to buy besides the kit?

The kit box holds the foam, the gun, a cleaner and some protective gear, and the rest is a short list: a cartridge respirator if the box only has a mask, plastic sheeting and tape, a spray bottle, a long knife or saw for trimming, and extra cleaner for a job that runs over several days. The list of what you need for spray foam insulation sets it out item by item.

Do you need to cover spray foam insulation?

In a room people use, yes: the building code expects foam plastic to sit behind a thermal barrier, most often half-inch gypsum board, with narrower rules for attics and crawl spaces used only for service. The guide to ASTM E84 Class A spray foam explains what a Class A result does and does not excuse.

Which kit should you spray?

The kits above share most of their instructions, so the choice turns on the documents behind each one, the box contents and the price. The spray foam insulation kits ranking orders them by what each maker publishes.