It’s one of the unwritten rules of remodeling that a project will always cost more and take longer than expected. Unlike the many HGTV shows now, jobs don’t always work out exactly on time, and problems don’t simply resolve themselves over a commercial break.

But just because this may be the norm, you don’t have to take it as a given. With the right combination of planning, discipline and smart shopping, your renovation can end on budget and ahead of schedule. Here’s how to get there:

Build a cushion

Hidden surprises, including structural damage behind walls and outdated electrical, are the biggest remodeling budget busters. Building a 10 to 15 percent cushion into your initial budget will help cover these unforeseen issues.

Involving your contractor early in the process also helps set a realistic budget. While they can’t see through walls, they might be able to do a pre-inspection of the house to spot potential problem areas. A spongy floor or spotted ceiling, for example, is a sure sign of water damage.

And be careful not to fall in love with a design that’s way beyond your budget.

Negotiate upfront

Most contractors are willing to negotiate over the price of the job. That’s especially true if they know you’ll turn into a repeat customer, so if you have additional projects in mind, be sure to share that information upfront.

Getting bids from multiple contractors will increase your bargaining power. You should also check HomeAdvisor’s True Cost Guide to get a handle on the current market rate for a given project. As with any deal making, the more information you have, the stronger your position will be.

Stick to the plan

It’s often said that the four most expensive words in home remodeling are “while we’re at it.” If you’re intent on sticking to a budget, you must resist the urge to change the design plan after the work is underway.

The more detailed the design up front, the easier this will be. Avoid a lot of “allowances” in the written contract — basically blank spaces that your contractor will fill out later, say for light fixtures or flooring materials. It’s easy to underestimate how much these items will cost.

Resist the urge to change the design plan after construction has begun if you want to stick to your remodel budget. Change orders can run up a project’s cost quickly and add unexpected problems as well leading to even more additional costs.

Do some of the work yourself

DIY can help control project costs. Just be sure to make it part of the initial negotiations with your contractor. Low-impact prep work is ideal, like tearing up carpets or taking away old cabinets.

Unless you’re an experienced DIYer, think twice about taking a sledgehammer to walls. Just because Chip and Joanna make it look easy, the work is messy and backbreaking, plus you run the risk of damaging load-bearing walls or buried plumbing and electrical lines. Believe me on TV they have had it all checked out and are only putting that sledge hammer to one little area for the camera.

At the back end of the project, finish-level painting is a great project to tackle yourself. Doing so could shave a few percentage points off the total budget.

Go bargain hunting

Salvage yards and second-hand stores can be great sources for inexpensive remodeling wares, from fireplace surrounds to sinks.

On a major project, like a whole kitchen renovation, however, while this may save you thousands of dollars, making used materials fit your space will present design and installation challenges, so it’s important to work with an architect and contractor with the right skill set and experience and let them know your plans early.