Wash Bay Framed in Wood 3

[KootK]

I'm reviewing a little addition to a car dealership. 1/2 of the space is dedicated to a wash bay. Cars come into get fixed and get a rinse down beforehand I guess. There is no architect on the project, just S/M/E. Owner's decision it seems. Everything is framed in light frame wood (studs & trusses). To my knowledge, there may not even be interior finishes.

How do we feel about durability with this? There's obviously a large garage door so I also worry about considering this a heated structure.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[oldestguy]

If this were my dealership, I'd use block walls, painted with water-proof paint on the inside. Check out the durability of treated wood. There must be a reason why treated wood foundation walls failed so early on.

 

[jayrod12]

That's a terrible idea. even light gauge steel studs corrode in that atmosphere.

 

[KootK]

You guys have echoed my initial thoughts. However:

1)Googling has led me to believe that full blown car washes may have been constructed in wood previously.

2) I've seen faux wood homes built over top of residential neighbourhood waste water treatment plants. Usually very specific, and durable, interior finishes however.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

Car Dealership owners are a unique brand. If they are made aware of the risks and durability of using a wood wall, why not let them if you add disclaimers? We usually build ours out of precast concrete or steel.

 

[XR250]

Seems like a bad idea. I guess if push comes to shove, use pressure treated lumber and stainless fasteners.
Def. would not use light gage steel.
I would push for masonry

 

[KootK]

Thanks for all feedback guys. The lack an architect on this is part of what concerns me. I feel as though the engineering consultants may be inadvertently -- and unwisely -- taking on the liability for the aspects of building design that an architect would normally tend to.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

What is the size of the existing building? If it is over 6,600sq ft and there is no firewall I doubt they can avoid using an Arch.

 

[BUGGAR]

I think I would tell the owner that I could get him a used bounce-house that would likely last just as long.

 

[BUGGAR]

PS.: Dealers wash your car before you pick it up after servicing. Read those dealer business bulletins and their psychology of customer relations. If your car is clean after servicing,

 

[allgoodnamestaken]

I've been involved with some small equipment (snow plows, etc) washing sheds. We used wood frame but we also mitigated the water issues a bit.

- Wash curtain on a rail that hangs from the ceiling to near the floor to protect walls
- sufficient clearance between walls and curtain for any splashes that the curtain doesn't catch (I think we used 3' or 4')
- Exhaust fan attached to humidistat to keep the room as dry as possible, automated air intake as well to ensure air quality for people working in the building
- Sufficient floor slope away from walls to protect against pooling of water
- Floor slope led to a trench drain leading to a sump pit leading to storage container (so you don't dump detergent/chemicals into the sewer - check requirements in your jurisdiction)
- concrete ledge all around the building perimeter to lift the wood frame above the finished floor level
- foam sheet insulation in the walls so that water intrusion didn't cause permanent damage
- Our interior finish was painted galvanized metal liner panels to minimize corrosion, and could be removed without damage (they screwed into girts running horizontally on the interior) in case you want to see what's going on in the wall or need to open the wall for repairs (although this never happened).
- Fully caulk the bottom wall seam

 

[hokie66]

I consider the lack of an architect an advantage.

 

[JAE]

Car repair areas are classified in the IBC as an S-1 occupancy and the car wash would be a type B. These do not need any separation according to the IBC Chapter 5 (see Table 508.4 in IBC 2012).

The IBC also allows wood construction for Type B occupancies. However, I might agree with the above that the constant water and soap might deteriorate the wood very quickly.

Check out Eng-Tips Forum's Policies here:
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[KootK]

I consider the lack of an architect an advantage.

Was waiting for that. Whatever we may think of their company/skill, they're great liability sponges.

What is the size of the existing building? If it is over 6,600sq ft and there is no firewall I doubt they can avoid using an Arch.

It's a wee little thing. You'd not be impressed. Love the curtain idea though, I'll recommend that.

- foam sheet insulation in the walls so that water intrusion didn't cause permanent damage

You really knocked this one out of the park -- thank you. I've got some of the stuff that you listed but not all. Can you explain the foam sheet insulation business a bit more? And how it prevents permanent damage?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[DBronson]

KootK:

I think most of the responses are on point - especially allgoodnames. However, the weak point in a system like this is the action of water vapour. The relative humidity in the space is going to be 100% much of the time and the vapour drive to the exterior will be huge. We did one of these about 15 years ago and it has worked pretty well. We used PT plywood sheathing on the interior of the studs and trusses, then covered that with Bituthene. The Bituthene was in turn covered with a FRP panel to protect the Bituthene and shed most of the liquid water. The Bituthene will keep nearly all the water out of the wall. The exterior wall materials need to be permeable so that when water does get into the wall (and it will) it can dry to outside. Work with the ME to control the RH and make sure there's sufficient insulation in the wall (and roof) to prevent the condensation plane from being too close to interior sheathing.

Regards,

DB

NB: Sheathing needs to be plywood - not OSB.

 

[KootK]

The exterior wall materials need to be permeable so that when water does get into the wall (and it will) it can dry to outside. Work with the ME to control the RH and make sure there's sufficient insulation in the wall (and roof) to prevent the condensation plane from being too close to interior sheathing.

Thank you very much for this DBronson. I'd been vacillating wondering if the wood should be sealed off on the inside or if that would just trap water vapour in. Now I see that, with the right exterior system, I can have it both ways: less water gets in and what does...gets out.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Archie264]

Regarding water vapor and membranes it's always good to review Joseph Lstburek's presentation on the topic, if you haven't already seen it. It sounds like DBronson has a handle on the issue though.

 

[KootK]

I'm not familiar with Joseph's work but I'll read up on it if you point me to a particular document. I googled him and he appears to be rather prolific.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Archie264]

Sorry about that. This is the lecture I had in mind:

https://www.youtube.com/watch?v=rkfAcWpOYAA

It's an hour and ten minutes but worth the time it takes to watch it and I don't say that lightly. It's very illuminating. And don't be put off by his style; he starts out very abrasively but it's all in good fun.

In my opinion the most important take away from it is to know that moisture moves from hot to cold and not to trap that moisture inside the structure, either by putting the membrane on the wrong side of the wall or locating it where a temperature change will cause condensation on the inside.

 

[KootK]

If you feel that the video is worth the time investment, that's enough of an endorsement for me. I'll make a point to watch it this weekend. Thanks for pointing me in the right direction.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.