The music video was directed by Kinga Burza and makes use of video, still shots and stop motion animation. Colourful everyday items such as toothbrushes, shoes, socks and toys (one of which appears to be a Yellow Power Ranger) are prominent.
It follows the song closely, and is made up of several main scenes; Nash playing a card game, turning in bed, eating lemons ("you've said I must eat so many lemons, because I am so bitter"), sitting on a staircase, arm wrestling, decorating a cake and sitting in her lounge. The video ends as she packs her suitcase and walks out of the house.
The song has received almost universally positive reviews from British critics. In August 2007, The Guardian gave the song a mixed review, citing its strong comparisons to Lily Allen, but praised the "indelible chorus". In September 2007, Pitchfork Media gave a positive review of the song, citing Nash's "gift for communicating confusing romance with a keen eye for detail and scene-stealing turns of phrase".
The Los Angeles Times also cited Nash's lyrical gift in Foundations in their review. In January 2008, Rolling Stone gave the song a positive review stating, "The rushed verses of "Foundations" – in which Nash dissects a couple's argument – convey sadness and snarkiness at once, and those verses sound pretty inviting, too." That same month, The New York Times gave the song an overwhelmingly positive review, hailing the song as her best and continuing with "The song is bright, peppy and mercilessly perceptive". In February 2008, Slant Magazine hailed the track as "energetic and borderline sadistic". In December 2008, Slant ranked the song at No. 17 on their list of the top 25 U.S. released singles of 2008.