carbon fibre i beam


I hope this is the right area to post this question, if not I am sorry. I am looking to change the 100 year old wood beam in my basement with a new beam. However there is very little room in the basement to maneuver a new I beam in place. I also considered building a beam out of 2x6 planks but I have been thinking there may be something better. What I would really like is a beam that is made from composite materials such as carbon fiber. Since the span is 20 feet and a jack post would be required at 10 feet if I use steel or wood, I was looking for a two section beam, both 10 feet in length with the jack post supporting both where they meet. If there are made from composite materials then the beams would be less labour intensive to put in place.

I was also wondering if it is possible to build a beam the doesn't have the top on it. This probably doesn't work but if it does then I can cut what ever inches are necessary into the girders and recess the beam with the girders sitting on the bottom lip of the beam. This would also give enough clearance to finish my basement as the only object that I end up hitting my head is the beam and I wouldn't have to dig out the basement more.

Do such building materials exist? I have been googling for some time now but no luck.



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Carl, Carbon fiber is incredibly expensive for that task. The CF cloth to make a 2x6 (1.5x5.5) would run at least $280/ft or over $5600 for your length. And I suspect a single 2x6 will not carry the load.

You would be much better off using "Engineered Lumber". Google is your friend.

Another issue, is that your Building Department is never going to approve a composite structural beam.

A beam with no top has no strength. DJ

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Mechanical Magic

I have seen composite beams made of laminated hardwood and softwood. They are generally 80% of the strength of an equivalent hardwood beam, but much lighter. The ones I have seen are made from reclaimed timber. I have also seen fabricated timber I-Beams. They consist of hardwood flanges and a ply or fibre board web. These are also very strong.

Visit some building design centres for some ideas.

Good luck.


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I fabricated a strong box beam from two twenty foot two by fours for caps and 12 inch deep plywood sides for boxed webs, with 2X4 internal struts every 2 ft or so. This box showed next to no deflection with two adults perched on the middle. I placed it over brick walls at each end and hung threaded steel hangers to straps on the existing ceiling beams, where a room had been enlarged, leaving a long unsupported ceiling. I can commend this approach. Depth is what gives a beam its stiffness though so you might consider carefully improving headroom by skimping on beam depth.

Brian Whatcott Altus OK

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Brian Whatcott


To adequately address your situation you need to let us know what load the beam needs handle.

Without knowing the load it is impossible to properly size the beam.

What's wrong with the existing beam? Its been in service for 100 years. What is the size (width & depth) of the current beam? What species of wood is the current beam? Is it supported mid-span?

Are you wanting to remove a post in the middle of the span? Reduce the beam depth to improve headroom?

You might be able to add heavy flitch plates to the beam and (if the design pencils out) reduce the beam depth.

Sounds like you're going to need an engineered solution.

If you do something wrong you could collapse your floor.

Your comment "....I can cut what ever inches are necessary into the girders ....."

cutting into existing timbers is not advisable unless you really know what you're doing.

cheers Bob

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