The International Cessna 170 Association

I think the only solutions to this are lots of ventilation, heat if you've got it, or a big dehumidifier if your hangar isn't drafty at all. I keep my heated hangar at 46 degrees in winter when I'm not there, but if the humidity is up I'll increase the heat to match the outside temps. Good time to be out there polishing or fixing things with the big door open.

Pretty sure that was actually moss, Arash.

After looking in a couple of more box hangars - my conclusion is - what George said. It's how well the hangar is sealed off.

My hangar is 50 x 60 with 3 inches of insulation over everything inside and a good vapor barrier under the concrete floor. The only time moisture forms in the hangar is when the air is cool inside and I open the door to warmer humid air outside and the moisture instantly condenses on all the cool things inside. When that happens, depending on the day, I just flip on the HVAC for a little while.

A common over-sight in hangar construction is the failure to provide a "ledge" for the lower edges of the R-panel/corrugated metal. If the lower edges are not sitting down on a ledge...or otherwise sealed-off... then humidity will likely always be a problem. If you have a 50- X 50 hangar, then each side has 50 two-inch holes to allow moisture and vermin access to the hangar. (Obviously, in wet climes the slab must also be poured over a vapor-barrier.)

This time of year my shop floor is often damp. The previous owner said they used Visqueen vapor barrier under the concrete but I doubt it. Besides the higher humidity level in the shop, the other problem is efflorescence. I've been told that one can use a concrete sealer as a moisture barrier. I'd appreciate the advice of those that know more about this than me, i.e. nearly everybody. If a sealer is the way to, any recommendations on what brand of sealer to use? Do I need to wait until the middle of summer when everything is as dry as possible to apply it?

Solicit the advice of a civil engineer on concrete slabs. There's more to it that pouring and smoothing. There's strength issues depending upon the ratio of portland to aggregate, etc. etc., and then there's the temperature of the day.. does it need retardant? or accelerator?..
Do you want 4-sack? or 5-sack? (If you don't know what that means.... get the advice of a civil engineer.)

hilltop170 wrote:My Port-A-Port hangar at Grand Prairie, TX, KGPM, was built on top of a sloping asphalt tiedown area. When it rained, water would run thru the hangar at an unimpeded rate which depended only on the strength of the storm. The previous owner simply poured a 2" slab of concrete on top of the asphalt inside of the hangar and leveled it off with respect to the lower 2" frame of the hangar. For $1200 about 10 years ago, that totally eliminated the problem and the hangar is bone dry except on those few high humidity days with condensation. ...

I'm working on my Port-A-Port tee hangar. Removing all the siding to wire brush the rusty frame with a grinder prior to painting it. I haven't staked it down yet. Prior to doing that I'm considering poring a concrete slab as Richard wrote about. The asphalt tie-down area where the hangar is located is sloping with several large cracks running through it. The owner of a nearby hangar says water percolates up from these cracks for two days after a good rain. So a couple of questions:

1.) As Richard said, the height of the lower frame in the hangar is two inches. If I pour the concrete to be flush with these beams, would that be thick enough? It seems quite thin for a concrete slab. I'll see what the concrete contractor says but if any of you have experience with this I'd appreciate your thoughts.

2.) Could someone with a 170B with lady-leg gear lay a straight edge along the spar sticking past the wingtip and then measure the distance from the ground to the bottom of the straight edge at the wingtip? A neighboring straight tail C-182 with 8.50-6 tires is parked in a hangar identical to mine. As you can see in the photo, the wing only clears the ceiling of the hangar by inches. The wing extensions on this tee hangar measure 7' 5" from the bottom of the ceiling square tube to the ground. If I pour a concrete slab thicker than 2" or add a couple of inches of insulation to the ceiling I'm concerned that I may have a problem with wing clearance.

3.) I was planning on using spray foam insulation to help keep the hangar cooler in the summer - which now seems to be April through September. But then I've been reading just how flammable that insulation can be. Any suggestions for alternative insulation or ways of mitigating the fire risk if I use spray foam insulation?

Sorry Gary I’m back in N.S. otherwise I’d go out to the hangar and measure. Never seen that type of hangar and I have to omit that’s rather smart.

Sitting level, on 6:00X6 tires at 24 psi.

Thanks George!

If you need to jack one wheel to make a wheel/brake/tire repair there simply will not be room with the hangar you propose. Additionally, if one tire goes “flat” in the hangar the opposite side may lose the available headroom. Just thinkin’…….

Hmmm, hadn’t thought of that. Need to get rid of the dihedral with some C-170A struts!