When you imagine a floor all you think of is the top layer. What is my floor going to look like in my home? But have you taken a moment to ask yourself what’s beneath the surface? Knowing about the full layout of your floor can be helpful in detecting damage and saving costs. So we’re going to tell you everything you need to know about subfloors. 


There are generally four layers that make a floor. The joist, the subfloor, underlayment, and the top layer. 

  • The joist is the first layer of flooring. Every floor has joists, with the exception of concrete. Joists are made of engineered wood, laminated wood, or dimensional lumber and are laid out as short columns to provide foundation to the floor above. 
  • The subfloor is the next layer and the first complete floor right above the joists. 
  • The underlayment is the next layer and it’s used as a cushion between carpet or laminate and the subfloor. Its purpose is to keep moisture from rising through the subfloor and increase noise dampening. 
  • Finally, the top layer is the floor you’re familiar with. By this point it doesn’t provide much structural support but it’s what brings the whole house together. 

What’s a Subfloor

Diving deeper into the subfloor, a subfloor is what provides the structural integrity of the rest of the floor. It is the first full layer of flooring above the joists. The type of subfloor one might build depends on cost, endurance, noise insulation, comfort, and cleaning effort.


The material used for subfloor depend on which level the floor is on. Below-grade, or basement/underground floors are usually made of concrete. Same goes for ground level if there is no basement. Above-grade floors, or floors above the bottommost level are usually made of plywood. 

Signs of Damage

Now that you know about subfloors, it’s time to learn about how to spot signs of damage. Here is a small list of things to watch out for, that could be signs of subfloor damage: 

  • Squeaking – if you’re walking around your floor and you’re hearing a lot of squeaking, then the subfloor underneath might be losing its integrity. 
  • Sagging – same thing goes for sagging. If you see sagging anywhere on your floor, that’s a sign that its losing its strength and is preparing to give in. 
  • Bad smell – if you smell something really bad and it’s coming from your floor, that’s a sign that your subfloor has attracted mold due to high moisture. 

Knowing these signs can help you spot problems with your floor more quickly, saving you a lot of time and money in the long run. If you see any of these signs in your home, call us immediately, and we will handle it.