# Damp concrete porch steps



## Rose Pink (Dec 15, 2013)

I am curious as to why the porch steps look damp when it gets cold outside.  Some parts of the walkway also look damp but not many. The entire steps look damp.  The concrete is about 25 years old.  Why the steps and not the driveway?


----------



## CO skier (Dec 15, 2013)

1 or 2 or 3 or combination (or many other, more obscure explanations):

1)  Water vapor condenses faster on relatively cooler surfaces.  The steps' surfaces cool faster than the walkway/driveway.  The condensed water darkens the concrete surface because there is less light refraction in wetted porous surfaces versus dry porous surfaces.

2)  The steps have a higher surface porosity than the walkway/driveway.  Water vapor that condenses on the steps can penetrate laterally across the surface of the steps faster than the less porous concrete of the walkway/driveway.

3)  A concrete sealant was applied to the walkway/driveway and not the steps.

What happens when it rains?  Do the surfaces darken at the same rate (instantaneous surface saturation)?  If they darken at the same rate, this would eliminate the concrete sealant explanation.

Are you sorry you asked?

Feeling experimental?  Take some Thompson's Water Repellent (available where paint is sold) and roll it onto the steps as if it were paint.  You will notice a dramatic difference in the phenomenon.


----------



## Carta (Dec 16, 2013)

Rose Pink said:


> I am curious as to why the porch steps look damp when it gets cold outside.  Some parts of the walkway also look damp but not many. The entire steps look damp.  The concrete is about 25 years old.  Why the steps and not the driveway?


============================
Are steps covered by a roof / carport? If so, condensation builds to create dampness...Just a guess


----------



## Rose Pink (Dec 16, 2013)

Thanks for the replies. I had considered condensation but thought if the steps were wet from condensation, why not the sidewalk leading up to them? I hadn't thought they might be of a different porosity or type of concrete. 

Also, the air is so dry here that I don't think there is much moisture in to condense in the first place. The temps have stayed below freezing for a few weeks now. At times water does drip from the roof/gutter due to ice dams that DH is trying to address (but ran out of time before the last snowstorm) but that doesn't seem to be the case at present. 

I see that DD put some ice melt crystals down so they must have had a layer of thin ice on them this morning. It hasn't snowed so there is no new moisture in the air or on the ground to account for the moisture on the steps. 

The steps are not covered. The porch is under an overhang and it doesn't seem to get wet like the steps do except for the outer edge and then down the steps. Then the sidewalk has a few darker/wet spots but not nearly as much as the steps. 

I don't think any of the concrete has a sealer on it. I will definitely try to seal the steps when the weather gets warmer in about 5 months or so. 

I ask this question because I eventually want to cover the porch and steps with pavers or stone with a heat cable under the veneer to keep the snow and ice away and I don't want to be covering up a damp problem that will cause more problems.


----------



## CO skier (Dec 16, 2013)

Rose Pink said:


> ...
> Also, the air is so dry here that I don't think there is much moisture in to condense in the first place. The temps have stayed below freezing for a few weeks now.
> 
> I see that DD put some ice melt crystals down so they must have had a layer of thin ice on them this morning. It hasn't snowed so there is no new moisture in the air or on the ground to account for the moisture on the steps.



Do the cars parked overnight on the street have a thin coating of ice in the morning?  If so, there is enough moisture in the air to condense and create the effect you are seeing.



Rose Pink said:


> ...
> The steps are not covered. The porch is under an overhang and it doesn't seem to get wet like the steps do except for the outer edge and then down the steps. Then the sidewalk has a few darker/wet spots but not nearly as much as the steps.



This is a sure sign that what you are seeing is due to moisture condensation from the air.  The steps will begin to look damp at about the point where the porch overhang ends.  You may also notice that concrete that is away from a building (heat sink) and is in shade most of the day will look damp, whereas concrete that receives sunlight most of the day will not look damp (the moisture is condensing on the cooler concrete before it condenses on the warmer concrete).



Rose Pink said:


> ...
> I don't think any of the concrete has a sealer on it. I will definitely try to seal the steps when the weather gets warmer in about 5 months or so.
> 
> I ask this question because I eventually want to cover the porch and steps with pavers or stone with a heat cable under the veneer to keep the snow and ice away and I don't want to be covering up a damp problem that will cause more problems.



If you will be applying the pavers or stone within the next two years, you would want to skip the sealer now, as it might cause an adhesion problem.  (Probably not, but it is better to play it safe).

Consult with a good stone mason, but it does not sound as though you have a moisture problem from the ground that will cause a problem with your plans.


----------



## Rose Pink (Dec 16, 2013)

Thanks!  Yes, we do get frost on the cars.  That point had not occurred to me. 

 I think I need a good landscape architect to help me plan this all out and find some good contractors.  I am in over my head.


----------

