Almost four out of 10 homeowners go over budget when doing a remodel, according to a 2014 report from home improvement site Houzz. Another stat that’ll make you think: Only one in five comes in under budget. Protect your bottom line with these five tips:

1.  Reconsider DIY

DIY is cheaper, right? Not necessarily, says Philadelphia-based interior architecture and design expert Glenna Stone. Depending on the project, amateurs beware.

“If you don’t have the expertise, you could end up paying between 10% and 40% more,” Stone says.

Why? While your DIY labor is technically free, your lack of know-how can be costly.

And then there’s hiring and scheduling. A task like moving a wall could mean hiring an engineer and an architect, not to mention coordinating permits. A general contractor knows who’ll do the best work for the best price, and they’ll know when to schedule them to avoid wasting dollars on inefficient use of time.

“If the plumber comes out before you’re ready for him, they’ll charge you for that visit, and then to come out again,” says Stone.

Finally, a contractor is more likely to get it right the first time. There’s nothing like having to buy stuff twice because you messed up. Stone recommends hiring a general contractor for most medium- to large-scale jobs.

Takeaway: Don’t DIY unless you really know what you’re doing. Mistakes cost more than hiring a pro the first time.