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I'd like to create a small storage space in my attic. The beam in Red is low and just gets in the way. Can I remove one of the Red beams without causing structural problems? I am willing to put in supports on the sides like the white post I have pictured. I'm also willing to move the Red beam up, but it would have to be all the way up at the ridge to be out of the way.

beater
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Probably not. For a definitive answer you can bet your house on (which you will be doing), consult a licensed civil/structural engineer.

The "white post" does not fulfill the same function that the "red beam" does (making strong/rigid triangles to resist forces from the roof loads.)

Ecnerwal
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    This, 1000 times, this. The red beam is in tension (sideways force). The white posts (primarily vertical force) do almost nothing to relieve the load that's on that cross beam. – Doresoom Jun 08 '15 at 19:04
  • Even then I've seen structural engineers make mistakes. Granted their bonding & insurance paid for the repairs but it was dangerous for a couple of weeks while it got noticed and sorted out. (Roof sagging for HVAC unit there was a bad calc) Point being. It's not a good idea to mess with engineered trusses. Nowadays things are engineered to the minimum which means taking one out can have consequences. – Dano0430 Jun 08 '15 at 19:17
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    While they are not infallible, they are trained, licensed and insured professionals, which increases the odds of a suitable outcome (even in the generally rare case of an error) considerably over "some guy on the internet said it would be fine." – Ecnerwal Jun 08 '15 at 19:27
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    @Ecnerwal - but the advantage of taking advice from "some guy on the internet" is that you can almost always find some guy on the internet to agree with you, but much harder to find a licensed engineer tell you that it's ok to do something structurally unsound. Of course... it's much harder to get that guy to take any responsibility for bad advice, but the engineer is legally liable for his advice. – Johnny Jun 08 '15 at 20:26
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If the peak is a square joint (90-degrees), then you can get rid of the crossbar and replace it with a heavy duty corner brace. One type looks like this:

corner brace

Bisonbuilt.com charts about $120 for one of these, but if you buy more they are cheaper. You may be able to find something like this for less, but it will probably be at least $50 for a sturdy one.

I assume all the rafters in the roof have these crossbars. Taking one out is not going to have a big effect, but nevertheless, it is a good idea to put in a corner brace.

Tyler Durden
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  • I didn't leave the downvote, but are you sure that safe? Replacing a rafter tie that's a few feet down the rafter with a corner brace that extends only a foot or so down the rafter seems like it would dramatically increase the force that the brace (and fasteners) need to withstand -- even if the brace can withstand the force, the screws may pull out (with the brace you've shown, the screws are in tension versus shear loaded rafter tie fasteners). And I certainly wouldn't advocate removing a rafter tie entirely - that removes much (or all) of the rafter's ability to support the roof load. – Johnny Jun 09 '15 at 04:05
  • @Johnny First of all, every rafter has a tie, so removing just one isn't going to do anything, even if you don't add a corner brace. Secondly, as long as the corner brace is sturdy enough and is attached properly it will be stronger than the wooden cross piece. – Tyler Durden Jun 09 '15 at 12:12
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    I don't see how you determined that it's safe to remove a rafter tie from a simple diagram that shows only a single rafter and no roof structure. Using a corner brace you like suggested turns a rafter tie into a collar tie -- which serves a different purpose. One thing that's clear from his diagram is that the roof trusses are not acting as rafter ties. While his roof loading and design might be such that it's safe to remove a single rafter tie, it seems irresponsible to suggest that it is safe without knowing anything at all about the roof design. – Johnny Jun 09 '15 at 20:11
  • @Johnny Houses are overengineered. Not only could you remove the rafter tie, you could remove both of the rafters attached to it and nothing would happen. In fact, you could probably remove 5-10 of the rafters no problem. If you removed more than half the rafters, though, you might start to see some movement in the roof in heavy winds. – Tyler Durden Jun 09 '15 at 20:28