Open web floor trusses can save time, money
I’m sure you’ve driven across or seen large steel truss bridges that are made by combining any number of huge steel beams into right triangles that interconnect. When viewed from the side they look like open boxes with a diagonal piece of steel extending from one corner of each box to the opposite corner. Imagine how strong this design is to be able to hold countless tons of concrete roadway, cars, trucks and even giant train locomotives!
Did you know this same technology can be used in your home, room addition, light-commercial building and so forth? You can have these same trusses built using wood. I had my first experience with open web floor trusses made from standard 2x4s about 40 years ago. Ever since that day, when we installed these in a room addition, I was sold on the many benefits.
These magnificent trusses spanned almost 24 feet with no bearing walls beneath them. The homeowner wanted a giant basement recreation room with no silly support posts in the middle of the room.
The homeowner got involved in the design early in the planning stage. He was a giant of a man. He insisted that there be no bounce in the floor as he didn’t want to feel like he was walking on a spongy trampoline. The room above the basement recreation room was his master bedroom. He told me he wanted that floor to feel like he was walking on a thick concrete floor.
The software used by the engineers at the truss manufacturing plant allowed the designer to make the trusses stiffer than an old-fashioned
starched shirt collar. To achieve the desired strength with virtually no deflection, the trusses ended up being about 26 inches tall. The homeowner had a huge grin on his face when he walked across the plywood subfloor and there was no bounce whatsoever.
Another advantage floor trusses bring to the table is their flatness. Each one is a clone of the other. Normal dimensional floor joists are not always the exact same dimensions, and often they have crowns in them. A crown is a hump in a floor
joist caused by a natural curve down the length of the board. Problems arise when you install one floor joist that is flat next to another that has a half-inch tall crown. When you apply the subflooring, you immediately notice the floor is not flat.
All of the mechanical trades love open web floor trusses. You never have to drill any holes. HVAC installers and plumbers are able to install pipes and ducts just about anywhere in the trusses since the vast majority of the cross sections have wide open
space. You don’t have this flexibility with other engineered floor joists. I draw plumbing riser diagrams each week for homeowners, architects, builders and plumbers. Several times in the past year I’ve had to call the customer and tell them that it’s virtually impossible to pipe a bathroom as drawn by the architect. The plan calls for wooden joists and these products don’t allow holes to be drilled in specific locations close to where they rest on a bearing wall. You never ever have this problem with floor trusses.
To put some of this in perspective, allow me to share a more recent story. Months ago, a woman hired me to be her virtual general contractor for a house that’s being rebuilt in the northern forests of Maine. I was able to get involved in the early stages of planning and recommended using floor trusses for the lower level of the house.
These trusses were very long and rested on the foundation walls and two huge steel I-beams. Because she couldn’t find a plumber she trusted, she talked me into installing all the plumbing in this house. The vast majority of the plumbing is on the first floor and the required pipes are nestled within the trusses.
I can tell you that the trusses saved many days of labor, since I didn’t have to drill through any joists. The open design allows for faster installation of the pipes. What’s more, without the tall trusses, many of the pipes would have had to hang below the ceiling in the garage. Normal dimensional lumber or I-joists wouldn’t have provided enough room to accommodate the pipes and the pitch needed to get them to drain.
Using trusses saved this woman thousands of dollars, and she gets to have a nice smooth drywall ceiling in the garage with no exposed pipes. The alternative would have been clumsy soffits built at an extra cost to hide the pipes that hung below traditional or engineered floor joists. The radiant heat installer and electrician are extremely happy. The trusses will allow them to work much faster.
Firefighters dislike floor trusses. These products fail faster in a fire, putting firefighters in grave danger when they’re inside a house working or trying to ventilate a roof.
My suggestion to them is to stay outdoors and do their best to fight the fire. Fire departments can have the building department notify them each time a new house has these products. If it takes longer to extinguish the fire using a defensive posture, it just becomes a greater loss for the insurance company.