The TV executions break on 9 October, and continue the "Living UnLtd" strategy developed by the creative consultancy after Ikea moved its £8 million UK account out of St Luke's in November 2001.
The new spots will be supported by in-store activity and "fun sheets" outlining ways in which Ikea shoppers can perk up their home lives. They will appear in November and December issues of women's glossies. Media planning and buying is through MediaCom.
"Nosh" opens on black-and-white footage of overly formal eating occasions.
A public service broadcast-style voiceover announces a new trend, "noshing".
It then shows a couple eating in the bath, two ladies in face-packs scoffing snacks and other examples of people eating in informal settings.
"Shlomp" has the same austere opening, showing people attempting to sit up straight. It then cuts to scenes of unbridled relaxation, during which a woman slides off the sofa while reading her children a story, and an executive conducts a meeting on a reclining sofa. The two 30-second ads will also be backed with three ten-second executions.
The executions were written by Naresh Ramchandani and art directed by Dave Buonaguidi. They were directed by Brian Baderman at All Films. The "nosh" funsheet was photographed by Dan Burn-Forti.
The ads come as Ikea ploughs ahead with plans to launch a loyalty-card scheme, Ikea Family, aimed at design-conscious homemakers.
Karmarama's co-founder, Ramchandani, said: "We wanted to present Ikea's modern living ideas in a fresh and positive way while hanging on to the mischief that is part of the Ikea personality."
Ikea's external communications manager, Frances Evans, added: "The role of the communication is to encourage women to challenge the home conventions they are living in."