# Low Temperature Exterior Painting Questions



## ric knows paint (Oct 26, 2011)

leeave96 said:


> My Boys and I need to paint a wooden garage and here it is in December. We are looking at outdoor temperatures between 40 and 60 degrees through out the next few days. The building is already primed and ready for top coat, but the temps have fallen as per above. I've got Valspar exterior paint and the can says you can paint down to 35 degrees, but I'm a little worried even 45 or 50 degrees might be to cold for latex paint. BTW, the siding is T111.
> 
> Any tips, advice or suggestions for cold weather painting would be most appreciated.
> 
> ...


Hey Bill,

The best advice one could give for painting latex in cold temps is to wait until they're warm temps.

Given the temperature range you've described, you'd probably be OK to go ahead and paint latex with few problems...However, surrounding air is not the only temp you need to be concerned with. In order for a latex coating to coalesce properly, *air, product and surface* temps need to be above 35 degrees - during application and the critical few hours after. That means if the temp drops rapidly or frost settles during this dry time, some funky things can happen to that film. Evidence of a coating that has not coalesced properly may be splotchy appearance and premature chalking, little to no stain resistance, diminished flexibility that could result in peeling (which would only be a problem if you were to paint over a wildly expanding substrate such as, say T1-11 siding).

I sometimes kinda resent manufacturers that market exterior products as low temp - not because they don't work, but because they know their market will always push the limits of what's printed on the can. When we used to say "do not apply below 50 degrees", we knew people would be painting into the low 30's. Surprisingly, there really weren't that many problems doing that. But, now if we say "may be applied down to 35 degrees", how far do you suppose some will push this particular envelope? 

Coalescence issues are not easy to repair. If you experience problems, an existing coating that hasn't properly coalesced really doesn't provide a solid foundation for a new application of paint or primer next season if it's needed. 

As I said earlier, you'd probably be OK - but I'm always overly-cautious with temp-related concerns, and I HATE to paint things twice. Good luck and I'm sure you're gonna hear some opposing view points on this thread.


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## leeave96 (Jul 3, 2011)

The primer was rated for application no lower than 50 degrees and we were able to do that. I was suprised that the Valspar (Standard Exterior - 15 yr warranty) said you could coat down to 35 degrees. In our neck of the woods, it really doesn't get consistantly cold in the 30's until January, but we are creeping-up on it. We will get some days where we are in the low 70's. I may paint if the temps are upper 40's and going up for the day and pick warmer days as they hit my times off during the Christmas/New Years holidays. We will paint with quitting a few hours before the temps plunge for the night - leaving at least 2 hrs of upper 40 degrees temps.

Thanks again,
Bill


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## ronnoez (Dec 4, 2011)

I cant think of a better answer than the one Ric gave you, he really knows his stuff. It always amazes me the amount of calls I get here in Michigan from people just realizing they want to do exterior paint in November. Thats one thing you southern folk have on us Yankees; you can paint year round outside.....and golf.


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## ronnoez (Dec 4, 2011)

Oh, and thanks Ric for using the word coalescence in your reply. I've never used that word when refering to painting. I know what it means but I usually just step back and say "man I hope that sticks" LOL Being on this site is already paying dividens. From now on I might not be smarter, but I'm sure gonna sound like it.


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## mustangmike3789 (Apr 10, 2011)

I will have to agree with ric on this one too. After years of being a painter and now years of coating inspections, i have pushed the limits beyond recommendations and i continue to see products pushed to their limits. Manufacturers will give themsleves a little buffer on products to protect themselves and they also know that the products will be pushed past these limits. Here in florida, it is not uncommon to go weeks with the humidity in the 90's and put a stop on major painting projects. On several occasions contractors have had approval letters sent from a manufacturer giving an ok to paint in 95% relative humidity with a product that specifies 85% max. Im sure that these products can perform well in 95% RH with perfect dust free shop conditions or in a paint lab but things are much different on a dirty job site. High humidity or cold temps allow for more open cure times which can allow for moisture, dirt or other wind driven contaminates to be entrapped in the paint as it cures. Unless you are like me and have the proper calibrated tools to measure air temp, surface temp, paint temp, humidity and dew point temps, i would not rely on the weather forecast from the station that is 40 miles from your paint project. I will have to say that one of the tools that i use is a sling psychrometer just because everyone (jsheridan) seems to like it when i say it.:wink:


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## jsheridan (Jan 30, 2011)

Still haven't gotten my sling psychrometer fixed, I'll probably just buy a new one. I'm getting tired of borrowing the customer's. On the topic, it's best to err on the side of caution. Work from ten to two, which allows for morning dew to dissipate and gives time to dry before dark sets in. You're always taking a chance this late in the season. A friend of mine painted a bunch of large stucco walls the other day, and when the temps dropped, dew started in and the elastomeric was reactivated and started running down the walls and depositing on the ground. He was there at eleven o'clock at night with dry rollers trying to soak it up off the wall. A real mess I tells ya. Always err on the side of caution. 
Look for the other thread titled "Disaster", same problem.


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## chrisn (Dec 23, 2007)

jsheridan said:


> Still haven't gotten my sling psychrometer fixed, I'll probably just buy a new one. I'm getting tired of borrowing the customer's. On the topic, it's best to err on the side of caution. Work from ten to two, which allows for morning dew to dissipate and gives time to dry before dark sets in. You're always taking a chance this late in the season. A friend of mine painted a bunch of large stucco walls the other day, and when the temps dropped, dew started in and the elastomeric was reactivated and started running down the walls and depositing on the ground. He was there at eleven o'clock at night with dry rollers trying to soak it up off the wall. A real mess I tells ya. Always err on the side of caution.
> Look for the other thread titled "Disaster", same problem.


Glad to see I am not the only one with this problem,I cannot seem to find one @Blowes or Homely Depot either:whistling2:


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