Roof rafter installation

mathew stouffer · 02-22-2011, 08:02 AM

Best I could do with the pics in this space. Looks like this was going to be a hip roof in this area and there was some type of change on the fly

. At first I thought these were simple temporary supports for the rafters but then I noticed the rafters were 2x9, 24 inches oc. Does not look like an approved installation. Could not measure the span but looked like 15'. This is and attic in single fam home built in 2000. Any thoughts would be helpful.

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mathew stouffer · 02-22-2011, 08:17 AM

Here is the ridge beam.

mathew stouffer · 02-22-2011, 08:19 AM

Another pic.

**John Kogel** · 02-22-2011, 09:19 AM

I would probably mention some modifications like that to my client. Can't say if there is a real concern from the pics alone. It is hard to believe that whole adaptation was designed by a pro. I would recommend a search for the documents, permits, etc.

**Jeff Langhorn** · 02-22-2011, 09:58 AM

Wow, that looks like something you’d see in the deep back woods somewhere.

That has to be (is) amateur work. If the wood I’s were properly attached to the bearing and ridge plates then all those supports would not be required. Of course the I’s would need to be sized for the load.

This pdf explains using wood I beam for rafters. Start on page 18.

http://www.kentinternational.ca/brochures/Timberframe_System/TJI.pdf

JK gave good advise to go on.

mathew stouffer · 02-22-2011, 12:36 PM

Looks like someone threw a bunch of pick up sticks in the attic

Remember that game.

**Eric Barker** · 02-23-2011, 09:36 AM

It would be correct to write that the installation has unorthodox and improper aspects to it and that it should be further evaluated. I wouldn't see a need to go any further than that.

**Vern Heiler** · 02-23-2011, 11:10 AM

If you think that might have problems, take a look at this idea for a pitch change!

**Richard Burkard** · 05-02-2011, 07:01 AM

I've seen this type of installation before on a school building. Normally you would sheath the valley (top cord of the lower wood trusses) and then install valley wood trusses on the sheathed lower trusses. Then you would have an engineered roof system.
From what I can see in the pics there does not appear to be any restraint bracing, (diagonals) of the top cord bracing of the lower wood trusses. This is required in most building codes. See BCSI Guide to good practice for handling, installing, restraining & bracing of metal plate connected wood trusses or the HIB 91 addition for bracing wood metal plate trusses. I would also question the point loads from the verticle supports of the TJI's on the top cord.

I would strongly recommend an engineer evaluate this construction.

A building is only as strong as it's weakest structural link.

**Randy Mayo** · 05-02-2011, 07:48 AM

Mathew

My first guess is this was done on the fly without advice or approval. The concentrated loading placed on the engineered trusses below from the 2x4 supports from the upper roof is enough to throw the red flag. From a legal standpoint only an engineer can approve such modifications. If the upper roof was totally self-supporting and did not rely on the lower engineered trusses for support an engineer's involvement would not be needed.