When Is It Too Cold To Paint Outdoors?

When is it too cold to paint outdoors?

Driving through a neighborhood of new construction, and arriving at the finished house I was to inspect, I noticed something that disturbed me.

I saw painters painting the foundation walls!

That sets off alarms for me for SO MANY REASONS:

1.  It was 34F outside.  That is too cold to paint outdoors! 
2.  Does the painter not understand this? 
3.  Does the builder not understand this?
4.  Does the painter not care?
5.  Does the builder not care?

SO, WHAT ELSE HAS BEEN DONE IMPROPERLY OR WITHOUT CARE?

It's not a good way to arrive at a home inspection.  I was disturbed.  Greatly disturbed.

THE LABEL ON EVERY PAINT CAN SOLD, BY EVERY MANUFACTURER, THAT HAS THE MANUFACTURERS' RECOMMENDATIONS ABOUT WHEN THEIR PRODUCT CAN BE SAFELY APPLIED TO THE INTENDED SURFACE.

But you have to read it.  If you are a professional you are supposed to know these things.  If you are a supervisor on a building product you should be sufficiently informed about things like these.

SOMEBODY IS PAYING GOOD MONEY FOR YOUR PRODUCT.  THEY SHOULD GET WHAT THEY EXPECT AND ARE PAYING FOR.  APPLY THE GOLDEN RULE TO YOUR BUSINESS!

But, the question has not been answered.  When is it too cold to paint outdoors?

The rule of thumb is 50F or 60F, when using latex paints, at 50% relative humidity.  THE REASON FOR THIS IS CHEMISTRY.

Have you ever looked at the multiplicity of chemicals that go into the creation of various paints?  There are many, many!  And there is a reason for many, many!

Every paint contains chemicals that help it to stick to whatever the surface it is applied to.  These chemicals are called SURFACTANTS.  Whenever you see peeling paint, the reason has to to with its application - what it was painted over, the temperature during its application, the kind of paint being painted over another kind of paint - whatever.  PAINTS WILL PEEL IF THE SURFACTANTS CANNOT TAKE HOLD.

If you speak with a paint chemist (and I have called one to ask these questions!) to find out why there is a temperature range for various paints, the answer will be something like this:

As paint dries its components need to "coalesce," literally melting together.

When it is too cold dew forms on the paint, particularly at the end of the day, and this humidity mixes with the paint components.  The paint stops coalescing.  The surfactants are encouraged to leach out, coming to the surface.

The end is that as the moisture evaporates, the surfactants cause staining, and the paint will have adhesion problems.

To the right is my client's house.  They peeled back the turf, and sprayed, blowing dirt and mulch onto the wall in addition to the paint.  It is 34F.

WHAT A WONDERFUL JOB.

Do you see the sarcasm drip from the statement above?

The local paint manufacturer most used by companies here is this one.  Look at what their label for the paint used here says about application temperature - 50F to 125F.  The other popular company around here has a similar label recommendation.

My client says they painted the doors and shutters at similar temperatures.  Excellent!

My recommendation:  home inspectors are objective in their knowledge, opinions and recommendations.  They aren't under time line pressures, budget constraints, personnel management, and if they are ignorant about something they will likely find out!  So ask questions of them!