The phrase "add on a week" is correct and usable in written English.
It can be used when discussing extending a time frame or duration by an additional week.
Example: "Due to unforeseen circumstances, we need to add on a week to the project timeline."
Alternatives: "extend by a week" or "increase by a week".
Some volunteers add on a week's vacation and then deduct a prorated part of the airfare.
When you think that you can add on a week of rest and recuperation somewhere, like on the exotic island of Langkawi, in a 5-star hotel, and still save $10,000 on what it would have cost you in the U.S., it's no wonder that Malaysia's medical tourism industry is on the rise.
In short, religious men and women physically separate during the days of menstruation and add on an additional "clean week," making about 12 days out of the month in total.
Want to climb Mt. Kilimanjaro but then maybe add on a week-long safari afterwards?
You may be able to store up your vacation time to use to either start your parental leave early or add on a few weeks after the baby is born.
However, by the end, the VIEN undergraduate researchers were all wishing they could add on a few extra weeks to the summer.
A Washington Heights resident, he said he preferred New York to Los Angeles "because you have more access to stage time," adding: "On a slow week I'll do two New York shows.
While Ronaldo's reported £80m fee outstrips Kaka, it is understood he will earn a salary of around €8m net (£6.8m), which when Spain's non-domicile tax rate of 25% is factored in is close to €211,000 (£180,000) a week before add ons.
Add on another week if you plan on visiting the Golden Ring towns, the palaces around St Petersburg, and Novgorod, where it's best to stay at least one night.
Each week, the script kept adding on — almost as if the writers had an inside bet to see how far and wide the parody could stretch.
Lithium or placebo was added on a double-blind basis for 6 weeks to the drug regime of 62 patients with major depressive illness (in both hospital and primary care settings) who had failed to respond to a controlled trial of fluoxetine or lofepramine.
