Has anybody used a structural engineer?

[Don1357]

I'm in the outskirts of a town in Alaska. I don't really need permits or inspections. What I really could use is a structural engineer to do a sanity check on what I want to do. I have never used one so I'm not sure if they are willing to do a consultation based on loose plans or if they only certify full plans.

I'm doing a 1 1/2 story workshop on a 24x36 slab, 2x6 framing. First floor with 10' ceiling, second floor a 3.5' knee wall with an open 10/12 roof with collar ties on the top 1/3rd (for wind load). Because of the open trusses I'm planning on two columns down the middle of the building 12' apart to support the roof weight. The construction type will be balloon, as only 2/3rds of the second story will have a floor (last third will be open for the eventual car lift) and the balloon construction allows me to stuff more insulation than regular stick framing. The seismic zone is D2, wind load is 110 mph with a wind exposure B, and 40 lb snow load. I'm doing the paper math for ceiling and floor joists but I have no practical experience with most of this so I would like to hire some expertize to save me from myself.

So far I had the insulated slab poured last year with 3 runs of PEX. I'm about to start two courses of 6x8x16 cinder blocks. Once I'm done then the framing can begin, provided I can sort out what I need to do

 

[anythingyoucanimagine]

I edited this to phrase it a little differently:

What exactly are you looking for? Just a general sanity check for your (loose) plans? Or something more specific like your sort-of trusses... There are span tables for common stamped dimensional lumber. Also if you use engineered products/materials, sometimes the manufacturer will stamp a specific beam. I did a little 12x20 ell ("L") addition (master bath off bedroom) over a slab on our house last summer. Weyerhaeuser was AWESOME helping me out with spans and stuff. They helped me a bunch even before I gave them my credit card number.

I had everything electronic (sketchup) and scaled to my local AHJ's permit/plans requirements so I emailed the files to them. They certainly did NOT certify my plans but they did point out a few issues... especially when they could recommend better suited products they sell...

Everything I bought from them was stamped/certified individually which allowed me to put all the pieces of the puzzle together. (if that makes sense)...

I was doing two projects at once but I only spent about $1,600 with them ($800/house) and as I said, they were helpful even before I gave them my CC#. I was very happy/pleased with both their help and the materials.

 

[strutaeng]

I'm not sure if you could find someone in the nearest city (Anchorage?) Seems like you are in the right path doing your homework, which is good.

If no signed and sealed plans are required, perhaps just a consultation will be enough. He or she may need to sign and seal anyways, depends on state board rules, even if the county does not require it.

Being that you are in a high seismic region, I would be more concerned about the connections, besides the size of the members, both of which the engineer will size and detail properly on the set of plans.

You can see if you find someone on the here:

https://www.commerce.alaska.gov/cbp/main/Search/Professional

or your local search engine.

 

[Nick in WI]

Where do you plan to purchase the materials? In my experience most suppliers will draw you up plans for free if you're purchasing the materials through them but if you don't follow through with the purchase they will then charge you for the plans.

 

[xyster101]

Post some plans here. Plenty of experts and people who think they are experts will give you all kinds of useful and useless advice. Seriously it will end up good stuff.

 

[paredown]

We've had to get engineering stamps on some projects where structure is involved, like the house that we put an elevator in. Sometimes the stamp is almost pro-forma, where he will tell my partner to do the preliminary drawings which he will then review and stamp.

Sometimes he will want to dig in and do plans from the ground up. Either way these will get submitted for permits where we work.

OTOH, a surprising amount gets figured out on renovations when the walls are open and the problems with 'theory' meet reality.

That said, I would run your plans by folks on the forum, but if you have access to an engineer, it wouldn't hurt to have him do a look-over--our guy is not prohibitively expensive.

Your description makes it sound like your project is a little more complicated than a simple stick framed garage--plus you have both snow load and wind shear requirements to take into account, so I would lean towards getting a look-see.

 

[DFB]

I've worked with structural engineer before. Some of the jobs my bud and I have done needed an engineer stamp for building code approval. Wasn't too expensive sounds like it be worthy investment let them do the major load calcs for you such as sizing out those 2 support columns you want with that 36 ft span

 

[Don1357]

Sounds like the next step is to visit the builder supply store for more info and to see what suggestions they can provide.

The thing is: there are plenty of online calculators for spans and trusses and joists and everything inbetween but I don't know what I don't know. Most of the time the trick is to over engineer with stronger products but because there are so many different pieces to this puzzle, I would feel more comfortable with somebody that knows this stuff to shake the stupid out of the paper and pencil drafts

Once I do more calculations I'll see if I can scan and post what I have in mind so far.

 

[Samh]

I'm in the outskirts of a town in Alaska. I don't really need permits or inspections. What I really could use is a structural engineer to do a sanity check on what I want to do. I have never used one so I'm not sure if they are willing to do a consultation based on loose plans or if they only certify full plans.

I'm doing a 1 1/2 story workshop on a 24x36 slab, 2x6 framing. First floor with 10' ceiling, second floor a 3.5' knee wall with an open 10/12 roof with collar ties on the top 1/3rd (for wind load). Because of the open trusses I'm planning on two columns down the middle of the building 12' apart to support the roof weight. The construction type will be balloon, as only 2/3rds of the second story will have a floor (last third will be open for the eventual car lift) and the balloon construction allows me to stuff more insulation than regular stick framing. The seismic zone is D2, wind load is 110 mph with a wind exposure B, and 40 lb snow load. I'm doing the paper math for ceiling and floor joists but I have no practical experience with most of this so I would like to hire some expertize to save me from myself.

So far I had the insulated slab poured last year with 3 runs of PEX. I'm about to start two courses of 6x8x16 cinder blocks. Once I'm done then the framing can begin, provided I can sort out what I need to do

You say open trusses, but it sounds like you are talking just regular rafters with collar ties in the top 1/3? Are you planning on running a ridge beam? If so, you should be able to get the correctly sized beam from the Lumber yard, as they usually run it through a computer.

If you are going to run courses of cinder blocks, I would almost run enough so that the portion of wall that will have floor above it is 8ft lumber, then you can run 12ft lumber for the rest. Assuming that isn't what you are already planning on doing.

 

[rharman]

Maybe talk to a local architect? They must have an engineering firm they work with. Might cleanup your design too. They can probably help you avoid many pitfalls.

 

[matt_i]

Typically the roof structure is going to be automatically analyzed if you purchase trusses. They have engineering software which bakes in the 40psf snow load, wind load, etc.

Relative to wind load, design-for-uplift is a very common thing in all areas of the US now, it involves reinforcing the load path all the way from the slab to the roof. Simpson Strong Tie has all sorts of stamped/folded sheet metal connectors just for such occasions, amongst other competitors. Their H1Z truss connector is one that's very commonly used just to give one example.

Also, should you shingle, I would recommend 5 to 6 nails per shingle (4 is common). Very cheap insurance against wind issues as well as avoiding "high nailing" that doesnt penetrate the upper edge of the shingle just below to tie it in.

Relative to seismic issues I have no practical experience but you can see that when the earth shifts the building is basically a cantilevered structure with the max bending stress being right at the slab-to-framing connection. So generically beefing that up (not being knowledgeable of local codes) is going to be important. I would also recommend using flat metal "X" bracing on the interior of your walls to provide additional racking resistance....look at Simpson CS-16.

Lastly a good idea is to investigate Structural Screws...GRK makes the RSS screw and there's an ABC-Spax competitor. Anywhere you are going to toenail something...just don't because its an automatic weak point. There is a better way that might take a little longer to do.

 

[johninct]

Did I get this right : You are in Alaska and want to build a structure on a slab with no footings below the frost line?

 

[DFB]

Alaskan slab!

 

[Stuart in MN]

Did I get this right : You are in Alaska and want to build a structure on a slab with no footings below the frost line?

Floating slabs are often used in cold climates, including Alaska.

 

[DFB]

Floating slabs are often used in cold climates, including Alaska.

I am curious though about how column footing is done on such a slab for a center girded and joisted upper deck load

 

[paredown]

Typically the roof structure is going to be automatically analyzed if you purchase trusses. They have engineering software which bakes in the 40psf snow load, wind load, etc.
...

Our most recent job for Habitat, we switched from rafter to truss (to go easy on the old guy carpenters like me), and the truss company does all the calculations for the local requirements (as you say), and then sends a stamped drawing directly to the permitting authority, who accept it without question.