carport rafters and bearing wall relocation

**oifla a** · 02-03-2014, 11:52 PM

Hello all

First time poster looking for advice.

We have a carport that is annoyingly just narrow enough not to allow us to park both our vehicles under it. The span of the existing rafters is ~13'6" from the house wall, where they are anchored, to the bearing wall pictured below:

If I could relocate the bearing wall at the end of the rafters (to just under the gutter in the picture) I could squeeze both cars in without much trouble. The problem--and there's always a problem with stuff like this--is that most of the rafters do not continue past the bearing wall. That is, the little overhang that is visible in the pic (between the bearing wall and end of the roof/gutter) are shorter pieces nailed in between every few rafters. In short, most of them are 'dummies' (there's probably a term to describe those but I don't know it) and only a few rafters span the whole way.

So, the question is: can i double up on the existing rafters and/or reinforce them in some way that would allow me to move the bearing wall further out? Thanks

**Dom D'Agostino** · 02-04-2014, 06:24 AM

There's always a way to re-do structure. But you have to do it safely, and it depends on how big a check you want to write.

Your carport looks like 2x8 rafters on 24 inch centers, so it's already at or just above it's span rating.

Have a carpenter give you a estimate based on what's actually installed, as there are far too many unseen variables in 1 or 2 photos.

**BridgeMan** · 02-10-2014, 10:11 AM

Why not consider inserting a new, full-length rafter midway between each of the existing rafters, and then splice (using moment-capable details) some new tails on the short members? You'd then have 2 x 8s @ 12" centers, which are able to easily span the distance you need for most species of lumber while being subject to 40 PSF liveload, 15 PSF deadload.

**Randy Mayo** · 02-10-2014, 03:20 PM

2x8 rafters at 12" centers could span about 15.5', however I have never seen an approved moment splice for solid sawn lumber. This assumes a 20 psf snow load, which covers most of your state except for the very northern part. If a center support beam and posts wouldn't be a problem, you leave the rafters at 24" centers and have two 11 foot spans.

**John Kogel** · 02-10-2014, 05:16 PM

If you sistered each of those 2X8 joists with a full length 2X10, then I believe you could then move the support wall to the outer end of the span.
The weakest point then would be at the attachment of the original joists to the house. The ledger board if there is one must be attached directly to the structural part of the house with lagbolts. If the original joists have any rot at the house end, then there needs to be repair work done there.

Use double wide joist hangers with all the nail holes nailed or screwed wih the right screws.

Then the exterior wall needs to be sheathed, with siding and flashing because it will be exposed to the weather. Build the wall so that the roof slopes away from the house, no ponds. Get a professional builder to do it and learn from him.

**BridgeMan** · 02-11-2014, 01:59 AM

"however I have never seen an approved moment splice for solid sawn lumber"

Perhaps you need to get out more. With proper splice members, and appropriate connectors, such a splice would be relatively simple to construct. Mid-span support columns won't cut it, unless one doesn't mind chopping holes in the roof of his car.

Thinking outside of the box is still legal, even though apparently not taught at your engineering school.

**Raymond Wand** · 02-11-2014, 04:26 AM

Buy smaller compact cars. Only kidding...

**Randy Mayo** · 02-11-2014, 07:47 AM

Hi, BridgeMan

Glad I got your creative juices flowing. The center beam design was for a (two) bay carport option with 11 foot bays, which gives him an option to salvage most of the existing carport roof. The existing roof is over spanned at 13.5 feet, so reducing the span to 11 feet puts the existing roof rafters within acceptable design criteria. As far as the moment splices are concerned, send me some info or a link for a solid sawn lumber moment splice. I would love to have that information, but it would have to have some solid engineering behind it before I would put my stamp on it.

**Randy Mayo** · 02-11-2014, 08:13 AM

oifla a,

If you widen the existing carport, pay close attention to the carport's connection to the house. This is typically the weakest link in most carport roofs that rely on the house to support one side.

**BridgeMan** · 02-12-2014, 11:18 AM

Mr. Mayo,

Let me see if I understand what you said--you want me to send you someone else's design and calculations, so you could then stamp them (with your P.E. stamp)? Wow.

Most state engineering licensing agencies frown on that sort of thing, and take strong disciplinary action against the perpetrators. Things must be different in Missouri, for you to be openly soliciting work done by others for stamping as your own.

**Randy Mayo** · 02-12-2014, 02:34 PM

BridgeMan,

Your taking this way to personal. All I wanted to see is if you have information on a design method not example, that is approved by the Nation Design Specifications for Wood Construction (NDS). The only information on a moment splice I can find is for Glu-Lam beams. I read on some structural engineering site the Eurocode may have an approved method for a moment splice, but I have not found it. Someone's example calculations are no good to me without some empirical testing data to back it up. Send me a website link, title of a design manual, name of a consulting firm, organization or individual that has design information on solid sawn lumber moment splices.