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Steeling the Show

Tom Silva strikes again! Replacing a load-bearing wall with an invisible beam.

<p>This Old House TV: Manchester house project</p>

This Old House TV: Manchester house project

One of the modern miracles of residential construction is the great open interior spaces made possible by beams made of steel and engineered lumber. The original builders of the McCues' house in Manchester used beefy timbers and full-dimension 2x10 joists, but the spans they were able to get were limited. The widest room was about 16 feet across, and its sagging joists were a sign that that was about the limit of their span, if not beyond.

While 16 feet hardly makes for a cramped room, the McCues' plan called for an open space nearly twice as wide to house their new kitchen, which had always been stuck at the far end of the east wing. Integrating the kitchen with a family-room area on the first floor was a key element of the overall design for the renovation. Not only does it take better advantage of the spectacular harbor view, it's also a nod to the more central role the kitchen plays in the modern lifestyle. All that stood in the way was a wall.

From a structural standpoint, however, this happened to be a very

important wall. Bearing the load of the second and third floors above,

as well as part of the roof, making this particular wall disappear was not exactly the average do-it-yourself project.

What I needed of course was something that would carry a massive structural load but remain virtually invisible. The solution: a large steel I-beam. A steel beam is great because it offers a lot more

load-bearing capability without the increased height you would need in a wooden beam of similar strength. And that means less intrusion into the space we're trying to create.

For this project, we used a w14x82 steel I-beam. These numbers have to do with the beam's carrying capacity. The first number tells you that beam is approximately 14 inches high (the w stands for "wide flange," which refers to the shape of the cross sections on the top and bottom of the beam). The second number indicates the beam has a weight 82 pounds per foot. An engineer uses these and several other considerations to determine what size and dimension of beam is needed to carry a certain

floor load. *

The key to using an I-beam like this for a house project lies in modifying it to connect with the existing wooden floor joists. To accomplish this, we filled out both of the beam's webs with laminated veneer lumber (LVL) to be even with the width of the I, three continuous glued layers on each side. An additional length of LVL along the top will help prevent the beam from squeaking as it comes in contact with the subfloor above. More importantly, once the beam is installed, the LVL lets us attach timber hangars that tie into the floor-joist system.

But first we had to coax and bully the giant into place. One of the very

first things we did ahead of time was to build a platform just outside

the wall at the level where the beam would enter the house through a

carefully sized hole we cut in the side of the house. The platform was

also where we actually put the whole thing together, so the platform had

to be strong enough to handle the weight of the fully assembled beam

— at about 30 feet in length and fully padded out with LVL, nearly

4,000 pounds. So now we had to figure a way to get 4,000 pounds worth of beam from one side of the house to the other. For that we hired a crane. From the other side of the house the crane lifted the I-beam up and over and lowered it onto our scaffold. We did the same thing with the engineered-lumber pieces and completed assembling the beam.

Inside, we had already erected two temporary support walls on either

side of the wall that was coming out, taken down that wall, and to make

way for the incoming beam, cut a slot between the old joists that had rested on the original wall's top plate. Still, getting the thing in was

a tight fit. So much so that as we pushed and pulled the beam in — with the help of a mechanical house jack — we had to shave away at the joist ends with a reciprocating saw to make extra room for the crowns of the beam's carriage bolts, which only protruded from the side of the beam by about 1/8 inch.

Finally in position, each end of the giant beam rests on a steel column

engineered to channel the entire load down, through special piers, into the footings in the basement. When all is said and done, the result for the McCues will be a great, wide-open kitchen and living space right at the heart of their home — perfectly suited for a modern family of four — and with a view of the Manchester harbor that's pretty good too.

As you'll see in the show, from curtain to curtain, making a wall disappear was hardly magic ... but we like to think it wasn't bad for a day's work either.

Tom Silva is the general contractor for This Old House.

CORRECTION: Thanks to two alert readers who pointed out that for a

w14x82 steel beam, the "w" actually stands for "wide flange," not "web"

— the verticle section of steel between the two flanges — as we originally stated. This Old House regrets the error.