deck design: I beam or C-channels

[llwor]

We like to do a deck at the back yard. The size is about 20 feet by 6 feet. The architect gave us a design for I beams and columes. But the steel manufacturer said that we could use the C-channels. Could anyone advice which way is better: easier in construction & lower in cost?

thanks.

 

[dik]

Without knowing additional information, it's difficult to reply.

Is the I Beam (Assuming it's a W or M Section) or Channel spanning the 20' dimension or is there an additional mid-span support?

Is there a guardrail and how is it fastened? Might be easier to attach to the web of a channel. The flat surface of the channel may be more attractive.

What is the deck construction? 2x6 on the flat spanning the 6' might be a little bouncy, or are the 2x6 vertical and is there sheathing?

How is the deck attached to the house?

The steel fabricator may have some surplus C Shapes that he wants to get rid of.

 

[phuduhudu]

I have just noticed having replied that we are in the concrete forum but I presume we are talking about steel here. Anyway here is my reply.

Structurally the I-beam is more efficient both as a column and as a beam so you are likely to get a lower weight solution for the same load than with a channel.

However, as dik pointed out the channel might look better at the edge and also give a flat web for supporting uprights for a guard rail. But if you are going to do that the uprights will apply torsion to the channel under load and any open section is not good in torsion. The guard rail actually needs careful thought as it is an item that structural engineers often leave to architects and architects often leave to installers.

The other issue with the deck is it's lateral stability which dik hinted at by asking if it was connected to the house. All in all make sure your architect has had structural advice on this. Carl Bauer