Being a custom home builder in Alachua, Fl since 2015, I've seen many customers cut areas and then regret it, and I've also seen how important certain areas to my clients when we are designing plans and their previous home didn't have enough space in these particular areas.
1. Walkspace In Your Kitchen. When Islands became extremely popular in the 2000s, it cut down quite a bit on the amount of space people had to work with in their kitchen. The main thing you want to be sure of is that you're maintaining a minumum of 36" of clearance from countertop to countertop, and you want to be sure that the 36" minimum walkspace holds true especially where the fridge is, as this will be one of the busiest spots in your kitchen, so you'll want plenty of room to operate. Oftentimes, when across from an island, I'll recommend a counter-depth fridge to gain an extra 6" of walkway and work space.
A Plan with Appropriate Walkspace in the Kitchen
2. Foyer Space. The foyer is often the first place guests come when entering your home, and will be the place you receive them. You'll want this area to feel inviting, and you don't want your guests to feel cramped. Ideally, a coat closet or coat rack will be nearby as well!
A Plan with a Large Foyer
3. Laundry Room. When designing a custom plan and running into budget concerns, the laundry room is typically one of the first rooms on the chopping block for many clients. But considering how essential a laundry room is to most homes, you'll want to consider how functional a laundry room can be. Some of the features you'll want to consider include: folding table, sink, hanging rod, and broom closet!
A Laundry Room with Many of the Recommended Features
4. Storage Room. For many draftsmen, adding storage rooms into a house plan can be a bit like a playing a complicated game of tetris, but storage closets are some of the most functional features you can add! Every household will have linens, coats, brooms, and there's always a spot needed to store christmas trees and other decorative and personal items. Storage closets always need to be considered, and if your plan doesn't have them, they need to be added in before completing the plan!