Sub Floor System: Framing Expertise For House Construction
A HOMEOWNER'S GUIDE
Ever wondered what's going on beneath your feet inside your home? I'm here to talk about something that doesn't usually get much spotlight but is crucial to your home's structure: the sub floor systems. These hidden heroes lie between your shiny top floor and the drywall below, and they play a massive role in your home's comfort and design.
What Are Sub Floors, Anyway?
Sub floors are essentially the backbone of your floor. They need to handle the weight of everything in your home and span across spaces without extra support posts or walls where possible. It gets pretty technical with all the structural engineering involved, so let's leave those details to the pros. What you should focus on is choosing the type of sub floor system that works best for your needs.
The Three Musketeers of Sub Floor Systems
There are generally three types of sub floor systems to choose from:
Conventional Lumber (2x12s and 2x10s)
I-Joists
Floor Trusses
Each of these options has its own pros and cons, so let's dive into what each one offers.
1. Conventional Lumber 2x12s and 2x10s
This is the granddaddy of flooring systems, having been used for centuries. It's readily available at most local lumber yards and is the most budget-friendly option. Most contractors know their way around this material, which speeds up the building process. However, it has a lower load-bearing capacity and a shorter span compared to the others. Also, be prepared for potential squeaks, as the narrow width can lead to misdriven nails or screws.
2. I-Joists
Introduced in the early '70s, I-joists have become a popular choice for modern builders. I-joist is an engineered wood product that has greater strength in relation to its size and weight. The biggest difference from dimensional lumber is that the I-joist carries heavy loads with less lumber than a dimensional wood joist. It uses 50% less wood than dimensional wood joists and is about 50% lighter.
The idea behind the I-joists was to help eliminate typical problems that come with using solid lumber joists, such as bow, crown, twist, cup, check or split. I joists' structural strength and little or no shrinkage help eliminate squeaky floors.
I-joists are not difficult to install and the market is familiar with it. Although it costs more than the conventional lumber, it is still very popular among home builders. Sometimes, when long spans there are small blockings installed across the middle of the joist to prevent bending when there is weight applied on top of it.
Insulation between I-joist
Insulating between I-joists can be tricky. The insulation material needs to be cut the exact size and shape of the between the joist area, otherwise thermal bridging will occur. That's why recommended insulation material for between the I joust area is closed cell spray foam insulation, that can add up to the cost but it will deliver the best performance.
A downside? The disadvantage is very rapid structural failure when directly exposed to fire. The lightweight nature of I-joists makes them more vulnerable to fire than dimensional lumber.
Floor Trusses
Floor trusses are structurally different from flour joists or conventional lumber. floor trusses are fabricated for individual projects specific requirements. like roof trusses, floor trusses are custom made for every single house. you can not buy floor trusses in your local lumber store like you can do with I joists or conventional lumber. Clear spans Floor trusses can be much longer than those of I-Joists.
Floor truss system: advantages and disadvantages
In terms of logistics it needs more advanced planning as manufacturers typically take time to produce it. They are made and delivered to the exact sizes, so once they are manufactured you can not change or modify the floor trusses. On the other hand I joists or the conventional lumber are delivered raw and then built on site. which generally requires more carpentry skill and takes longer, as carpenters need to adjust every single piece to the existing dimensions.
One of the noticeable differences is the utility installation. Floor trusses due to their open web design can accommodate almost any kind of HVAC, Electrical, and Plumbing configuration without compromising ceiling height in the house and without dropping any bulkhead in the rooms. Because of how easy it is to access utilities, builders and renovators can save time and money on the installation and maintenance of utilities.
Cost comparison
floor trusses are usually about 15% more expensive than the I joists depending on the area you live. but considering the ease of installation it can decrease the cost of framing as well as other utility installations such as HWAC and plumbing, as contractors will spend less time doing the work.
Something that all floor systems have in common is that during the installation they all require applying lots of glue between the plywood and I joist or floor truss and proper amount of nails or screws (in every 6 inches). as it can prevent squeaking noises in the future
After installation and during exploitation they all require regular checkups for mold, rot, insects, moisture buildup etc. it is necessary to make sure that your flour lasts a long time without squeaking, sagging and other malfunctions. Make an arrangement about this with your builder.