Conventional wood frame construction - 7 floors - feasible??

[TRBPA]

Multi-family residential client wants to look at going 7 floors using conventional wood framing for apartment "hi-rise". My max experience has been with 4 floors with slab on grade. This project would require piling or pier foundation at ground floor to get above base flood elevation, and have 6 floors (9'ceilings) of conventional wood stud-wall framing. Site is gulf coast (Katrina) zone with nominal 130 mph wind loading. Before seriously evaluating, was wondering what was max floors/height anyone else may have experience with, using conv. wood framing, any thoughts, comments, warnings, criticisms??

 

[dik]

They are looking at six storeys in British Columbia... a seismic area.

Dik

 

[mark1234]

You simply cannot do by code. Even if you could get it to work and no code stipulations it's just not a good idea.

Shrinkage, strength, etc.

 

[DaveAtkins]

I also don't believe the IBC allows this--not for structural reasons, but for fire safety reasons.

DaveAtkins

 

[abusementpark]

Construction quality for wood framed construction in Louisiana is bad enough on one or two story buildings.

What is your lateral force resisting system?

 

[kslee1000]

Other than code and fire concerns, which are absolutely valid and to be complied, the thought of highrise wood frame building is very interesting. Have you try to google, or try contact Japanese Engineering Society, which has rich experiences on both wood buildings and earthquake. I think to a certain extent, wood frame building is preferable over steel and concrete structures for its flexibility during earthquake event, and relatively cheap to build. However, the floor hight & beam spans would be quite restricted.

 

[racookpe1978]

Cheap to build? = yes.

Dirt cheap "undocumented" day-labor for 2x4 construction with no cranes or rigging and (now) dirt-cheap wood construction supplies. Only thing you need is an air compressor and a long hose for the air-hammers.

But dirt cheap construction and 2x4 stud walls can't give you the compression load and sideways rigidity for 7 stories. well, not safely at least. (I've been inside too many 2x4 nailed walls to be good about ANY of them above 2 floors the last ten years made by day labor and nails.)

Why not use steel columns at the corners and mid-span with beams between; then (exposed) wood beams beneath the floors? Puts up the frame fast (few crane rental days) and the day-labor rates can add the wood beams and floors. (Steel "2x4 studs" would be even lighter, faster). Lumber wouldn't be carrying the heavy loads from floor to floor to floor ...

 

[Ron]

Possible...yes
Feasible...somewhat (close to perfection required)
Practical...no

This is one of those areas that goes way outside normal practice, and if you do it, you'd better be as close to perfect as anyone can be....there's no standard of care in something like this, so in the event that something goes wrong (collapse in wind event less than code), you will be out there all alone. Unfortunately, it would likely be a situation of guilty (negligence) until proven innocent.

tight design
tight specs (including waterproofing roof and walls)
tight construction control
plenty of caveats and warnings...no hint of performance result, warranty, expectations to client
Limitation of liability in contract

 

[youngstructural]

I honestly see this as the next real challenge to Structural Engineering, and I have a number of drawings, calculations, and details already worked out.

I really am expecting this to be a big field, particularly in Canada (Yay Home!) and would be very keen to get involved in such a project. That is not to say that ALL of the caveats on this page do not apply, in fact they all DO apply! The reality is that the contractor needs to understand that they are producing a COMMERCIAL job, which must be handled to TIGHT guidelines.

I would also insist upon an experieced site engineer. NOT JUST PERIODIC REVIEWS. Actually I think the Kiwi standard of practice here would apply quite well: "We" are a PERFORMANCE based jurisdiction, so you can try just about anything if you can show that it works analytically. The code is not the final word... It leads to some amazing innovation. But I digress: I think that the New Zealand concept of a "Construction Monitoring, CM5 level" would be perfect:

"Maintain personnel on site to CONSTANTLY review work procedures, materials of construction and components for compliance with the requirements of the plans and specifications and review completed work prior to enclosure or on completion as appropriate."

Commentary:

"This level of service is appropriate for -Major Projects- where the consequence of failure are critical, Projects involving innovative or complex construction procedures. The level of service provides the client with the greatest assurance that the completed work complies with the requirements of the plans and specifications."

Lots of risk,
LOTS OF FEE REQUIRED,
But definitely somewhere we should aim to be!

Cheers,

YS

P.S. Please nobody eat me; It's just my honest opinion!

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[youngstructural]

Those high-tech mist sprinkler systems should be everywhere, on a highly failure-resistant, doubly redundant system. I would prefer the backup system to be gravit fed, possibly from a water tank ballast in the roof space. The system could perhaps be sized to ensure a minimum period of fire-fighting water supply, as well as to help fight any structural excitation under wind. After all, these will be very light-weight structures.

Cheers,

YS


B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[dik]

Catch the link:

http://www.cashsociety.net/media/APEGBC_Wood_Frame_Initiative.pdf

 

[msquared48]

Five story max here by code. Pacific Northwest. High seismic and moderate wind.

When the numbers are run, with the architectural requirements included, 5 stories is hard enough.

There would have to be code changes, no concrete topping for sound attenuation, and a lot more bearing walls, internal and especially external shear walls to make it work or the holddowns would become unworkable.

Mike McCann
MMC Engineering

 

[SKIAK]

I was always under the impression that, not considering wind or seismic, that conventional timber construction was impractical for the use of elevators. Thats a lot of load for wood framing.

 

[csd72]

The highest most codes will let you go is 4 floors.

Have you considered doing lightweight metal framing instead? Construction method is still almost exactly the same except the members can be ordered precut to the correct lengths.

Otherwise, can you steel frame the bottom 3 floors?

 

[msquared48]

Typically here, these structures are over PT parking. If the structure is higher than five stories over the parking, we just extend the PT up to meet the wood story number limit.

Mike McCann
MMC Engineering

 

[JAE]

The concern would be long term dead load creep. The wood will slowly, over time, shorten, causing distress in atached elements.

Also, for lateral load resisting systems (specifically hold-downs) I'd worry about the adequacy of the connections. Wood connections are always the biggest problem.