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Sika Mix-In-The-Bag Expanding Polyurethane Post-Setting Foam Fast Setting 33 -fl oz Repair accessory

Name: Sika Mix-In-The-Bag Expanding Polyurethane Post-Setting Foam Fast Setting 33 -fl oz Repair accessory
Brand: Sika
SKU: 999977070
Price: 16.98 USD
Availability: InStock
Rating: 4.1 (899 reviews)

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4.1

899

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Sika PostFix is a two-component, mix-in-the-bag expanding foam for supporting non-structural posts such as fence, mailbox, and signposts. This two-part, pre-proportioned polyurethane expanding foam has been specifically formulated to provide a lightweight, mix-in-the-bag, fast-setting solution. This high-strength backfill can be used for wooden, PVC, and steel in-ground supports.

Simple application - just roll, mix, cut and pour
Sets in as fast as 3 minutes
High strength and resistant to uptake of water
Seals and protects base of post
Compatible for use in cold conditions without the need for additives

General
Color/Finish Family	Green	Drive on Time (Hours)	2
Series Name	Mix-In-The-Bag Expanding Polyurethane Post-Setting Foam	Curing Time (Hours)	2
Type	Repair accessory	VOC Level	0
Base Material	Polyurethane	Dry to Walk	1-2 hours
Package Quantity	1	Paintable	Yes
Unit of Measure Quantity	33	Number of Coats Recommended	1
Unit of Measure	Fluid ounce(s)	Container Type	Bag
Application Method	Gloved hand

Features
Fast Setting	Yes	Lowe's Exclusive	No

Certifications
CA Residents: Prop 65 Warning(s)	Prop 65 WARNING(S) -

Warranty
Warranty	1-year

Compatibility
For Use on Concrete	No	For Use on Mortar	No
For Use on Stucco	No

Miscellaneous
UNSPSC	30111500

Check out the Best Selling Concrete, Cement & Stucco Mixes on Lowes.com

Review

4.1 out of 5

899 Reviews

75% Recommend this product

Ratings may include incentivized customer reviews.

Read All Reviews

+ 47

What Customers Are Saying

Customers overwhelmingly praise this product for its ease of use and speed, with no mixing or heavy lifting required and posts solidifying in under 30 minutes. Many report excellent results for fence and mailbox posts, appreciating the time savings and physical strain reduction. However, a notable group experienced failures under stress or environmental exposure, with posts becoming loose or shifting after curing. Some found the foam expanded unpredictably or reactivated after setting. Despite these concerns, most customers consider it effective for light-duty applications and would recommend it for solo DIYers.

Customer review summary generated by AI, including incentivized reviews.

899 Customer Reviews

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Made the brick walkway look beautiful

HalfordSeptember 26, 2026
Verified Purchaser

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Would Recommend

Worked great, very easy!

BwitchSeptember 23, 2026
Verified Purchaser

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Would Recommend

Good product worked exactly as anticipated. It expanded rapidly and showed good adhesion to the post.

Expanding PolyurathaneSeptember 21, 2026
Verified Purchaser

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great stuff

Would Recommend

easy to use when you dont have the time to mix concrete. sets within 3 minutes

DrewSeptember 18, 2026

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Great alternative to concrete

Would Recommend

I had to replace my old mailbox post, which was wood and rotten, and I chose this product because it seemed much easier to use than concrete. It was very simple to use and did the job very quickly. I watched a video on the company's website and followed the instructions. It needs to be mixed right next to the project and poured after 15 seconds!! I used a drywall saw to cut away extra after it was cured.

latkins616September 7, 2026
Verified Purchaser

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Sika: Featured Videos

COMPARE PRODUCTS

		Name	Current Item SikaMix-In-The-Bag Expanding Polyurethane Post-Setting Foam Fast Setting 33 -fl oz Repair accessory
		Ratings	899
		Type	Repair accessory
		Base Material	Polyurethane
		Fast Setting
QUIKRETE10-LB WATER-STOP CEMENT	Fast 2KPost Anchor Fast Setting 33.8 -fl oz Fast setting	Fast 2KPost Anchor Fast Setting 33.8 -fl oz Fast setting	SikaSelf-Leveling Expansion Joint Polyurethane Fast Setting 29 -fl oz Mortar Concrete Sealant	QUIKRETE20-lb Polymer Modified Structural Concrete Repair	SikaInstant Concrete Repair Fast Setting 10.1 -fl oz Mortar Concrete Crack repair	DRYLOKFast Plug Fast Setting 10 -lb Mortar Concrete Hydraulic cement	SikaHorizontal Rapid Repair Mortar Fast Setting 50 -lb Mortar Concrete Patch	SikaHigh-Performance Cementitious Grout Fast Setting 50 -lb Mortar Concrete Patch
479	395	346	528	119	69	103	2	2
Hydraulic cement	Fast setting	Fast setting	Sealant	Repair accessory	Crack repair	Hydraulic cement	Patch	Patch
Cement	Polyurethane	Polyurethane	Polyurethane	Cement	Polyurethane	Cement	Cement	Cement

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Sika Mix-In-The-Bag Expanding Polyurethane Post-Setting Foam Fast Setting 33 -fl oz Repair accessory

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