I'm currently renovating a house together with my fiancée and a colleague of mine. In the beginning we tracked all expenses and our planning in Excel, but that got messy pretty fast — especially the part where every cost has to be split three ways.
So I built an app for it. It tracks the expenses and automatically splits each one across the three of us. You can also photograph receipts and store them in the app, so nothing gets lost in a drawer somewhere.
Since then it grew a bit. Besides the budget we now also track defects and it generates a renovation diary, so there's a record of what happened when. I also added the meetings we have with the craftsmen — you can take notes during the meeting and file them under the specific craftsman, so you don't forget what was agreed.
Next thing I want to build is proper sharing, so your partner or friends can manage their own part instead of everything running through one person.
It's on the App Store at the moment. Play Store is planned but not there yet.
I mostly built this for our own renovation, so it's shaped around how we work. If you're in the middle of a renovation too, feel free to try it and tell me what's missing or annoying — happy to hear it.