FormExtender Ultimate Kit

A concrete form extender is a steel concrete forming tool that slides onto the end of a 2x4 form board to fill the remaining gap without cutting. It holds in place with a tension fit, so you don't need stakes, nails, or extra tools. This lets you use up the short boards you already have.

FormExtenders slide directly onto the end of your existing form board and extend to fill whatever gap is left. The tension fit holds the extender firmly during the pour, and when the job is done, it slides off and is ready to reuse. Instead of measuring and cutting a board to length, you grab the nearest shorter board and drop in an extender for the difference.

The Ultimate Kit includes 12 FormExtenders: three 6 in., three 12 in., one 18 in., one 24 in., one 36 in., one 18 in. with Gap, one 48 in., and one 60 in. That range covers everything from small gap fills to large, complex pours. It's the widest FormExtender kit MudMixer offers.

FormExtenders are built to fit standard 2x4 lumber, the most common board size used in residential concrete forming. They work for flatwork like patios, sidewalks, driveways, and hardscape borders.

Yes. The 18 in. Gap extender is made to form around fixed obstacles like sprinkler heads, deck posts, pavers, and plastic edging without removing them. You bridge the gap with the extender and keep your layout intact, which saves you from cutting a board to fit around the obstruction or pulling it out entirely.

FormExtender kits are available in person at Home Depot through participating dealers. Availability varies by location, so check the dealers page to find a stocking dealer near you. You can also order either kit directly through this site with free shipping on orders over $249.