Saturday they are available, but doesn't look like they are available on Sunday:
From Whitehouse.gov:
Public tour requests must be submitted through one's Member of Congress. These self-guided tours are available from 7:30 a.m. to 11:30 a.m. Tuesday through Thursday, 7:30 a.m. to 1:30 p.m. Fridays and Saturdays (excluding federal holidays or unless otherwise noted). Tour hours will be extended when possible based on the official White House schedule. Tours are scheduled on a first come, first served basis. Requests can be submitted up to six months in advance and no less than 21 days in advance. You are encouraged to submit your request as early as possible as a limited number of spaces are available. All White House tours are free of charge. (Please note that White House tours may be subject to last minute cancellation.)
If you wish to visit the White House and are a citizen of a foreign country, please contact your embassy in Washington, DC for assistance in submitting a tour request.