Manufactured I joists

[bigcountry]

I am in the begining stages of my cabin addition and was wondering if a manufactured I joist is better than using cut lumber?

[MountainDon]

What's the proposed span? To me, there is little reason to use engineered joists if the span is 16 feet or less; maybe even 20 feet or less, depending on what local lumber yards carry.

Of course the manufacturers of engineered products point out all the advantages and make it seem like their way is the only sensible way.

On the other hand, if you are a fire fighter you despise the engineered products as they burn up quicker causing building collapses sooner. Ditto on roof trusses vs rafters.

[davidj]

I ended up using I-joists for my place.  They were easy to work with - a bit more fiddly then dimensional lumber but nice and light so less effort to move.

But they cost a bunch more and didn't really give me much benefit (my spans are short and I only used them on the ground floor).  I'd use 2x10s if I was doing it again, just for financial reasons.  On the other hand, if I was doing a 20x30 with no central support then I'd do I-joist - a single I-joist is easier than two 2x10s and a wall any day (my place is a 20x30, but I needed/wanted a central support for other reasons so the I-joists are kinda wasted).

If you do use I-joists, try and line up the pre-scribed holes as it makes running wires/plumbing much easier later - no need to drill holes, just hit the pre-marked holes with a hammer.  I didn't do this and it meant dragging my drill with me when running wire.

[davidj]

Oh, one more detail with I-joists that is easy to miss.  You're not supposed to drill holes near the supports.  I.e. if you are running wires or pipes perpendicular to the joists, they need to be a foot or so in from the supporting walls.  I nearly missed this in the instructions as it's a subtle detail.   It turns out that this is a good idea anyway - running stuff right at the edge gets in the way of insulation or any other work on the wall.

[bigcountry]

Addition will be 24' wide by 30' deep. I am going to use sonotubes for supports 3 wide by 5 deep for a total of 15 supports. I guess using regular timber in this case will be more economical than the manufactured stuff....thanks for the help...

First time on this site....I have been reading it for a few days now and have really learned a lot and have gotten many ideas...

I will post pics of the addition starting in the spring...I hope its a short winter in NorthCentral PA!!

[psammy]

Dimensional lumber is dirt cheap right now.  I have been pricing a soon to be started house, and an engineered floor is running between 2-3 times as much (depending on depth of joists used).....2x10x20' for $15.20 versus $1.65/lin. ft. for a 9.5" I joist....for example.  A quick call to your local lumber yard should help you make a decision real quick.  Also, your addition at 24' wide is an ideal size for 2x10's with a beam/bearing wall down the middle and expensive for clear span eng'd joists (16" deep ~$3/foot).  YMMV.

good luck,
psammy

[John Raabe]

Welcome to the forum bigcountry! 

I think I would agree on your layout for a 24' wide.

[325ABN]

I used 16" TGIs to span my 26' walk out. Very quick and easy.