# Water coming in through siding



## paulf615 (Nov 2, 2015)

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I had insulated the wall in the pictures but I walked in the other day to find the bottoms of the insulation all wet. I took out the insulation and soaked that entire side of the shed and that part of the roof, in search for a leak. There was no leaks besides a leak where the bottom plate meets the floor. I don't believe a leak was the cause because it hadnt rained since I put in the insulation. My theory is that the wood siding is absorbing moisture from the air and bringing it inside. The reason I believe this is that side was one of the sides I didn't clean up and repaint so its covered in moss and It is shaded by a fence right next to it. I think sanding down the siding and repainting it would fix the problem. If you guys have different ideas on whats happening and how to fix it let me know. Any response will be appreciated. Thanks


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## nealtw (Nov 2, 2015)

Water will transport thru wood but ususally from cold to warm. Most siding will leak somewhere and that is why they used tar paper and now we use house rap, Just looking at theis wall a would suspect the boards above the wall in the gable end. First have a look at how water would run off the upper boards to the outside of the siding. You might be able to loosen the bottom of those boads and work in a flashing and and then cover those joints with a 1x4 and it would be board and batten.


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## beachguy005 (Nov 2, 2015)

If I were to guess, I would say that you heated the space and were working in it.  When you left and turned off the heat, the moisture in the air condensed on the walls, which were cold.


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## nealtw (Nov 2, 2015)

By the staining on the wood we can see the water has been running down inside this wall for years.


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## paulf615 (Nov 2, 2015)

beachguy005 said:


> If I were to guess, I would say that you heated the space and were working in it.  When you left and turned off the heat, the moisture in the air condensed on the walls, which were cold.



Nope never heated the shed and the other side of the shed was perfectly fine so I doubt it was condensation.


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## GBR (Nov 2, 2015)

Cedar siding wicks water, capillary action. I would paint the inside face of all siding to stop this action;http://www.articlesbase.com/home-an...-from-airspace-behind-your-siding-131102.html

If you had insulation on the wall, air temps are the same inside as outside EXCEPT the inside faces of the siding are now warmer due to the insulation, lowering the dew-point to cause your condensation, with no vapor barrier/retarder in effect to stop the condensation from the inside. 

   The paint seal between siding laps could stop moisture ingress there, if a vapor barrier was present. IMHO, add some tar paper/housewrap strips- stapled to the studs in each cavity, extending down past the bottom plate after removing the caulking for drainage. Leave an air-space as the link said, for help drying the siding. Add some mesh at the bottom plate from the inside- tapping siding out gently at the fastener locations... I see they used 2 nails on the lap siding where only one is required- may split a few boards, to add airflow to the cavities. Leave a bigger airspace to the foamboard. 

    If using 2" XPS, use unfaced and no vapor barrier is required as this warms the first condensing surface and severely limits moisture/air permanence through it. Add an ignition barrier per code, not OSB as this could mold with your occasional heat supply. 

I wouldn't add any horizontal trim boards... to trap water. Heat moves from warm to cold, water moves from wet to dry and toward a lower pressure (relative humidity= moisture content of the wood)http://www.thisiscarpentry.com/2010/09/03/moisture-content-wood-movement/, not temps- least I've never read that before... Lap siding needs the air-space (mini-rainscreen) and the pressure equalization benefit to stay dry; Fig'6: http://buildingscience.com/document...rainpenetrationcontrol/drivingrain/main_topic

Gary
PS. I would even add metal "L" flashing pieces in each cavity at the bottom plate gap resting on the plate with the tar paper extending onto this for positive water drainage...


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## GBR (Nov 2, 2015)

The fence could be creating a low pressure side by blocking the wind, or funneling the wind (high pressure) along that side to draw/force moisture in the air current in/out on that side only. Most likely blocking the wind. hence the moss covered siding, North or East side, correct?

Gary


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## paulf615 (Nov 3, 2015)

GBR said:


> Cedar siding wicks water, capillary action. I would paint the inside face of all siding to stop this action;http://www.articlesbase.com/home-an...-from-airspace-behind-your-siding-131102.html
> 
> If you had insulation on the wall, air temps are the same inside as outside EXCEPT the inside faces of the siding are now warmer due to the insulation, lowering the dew-point to cause your condensation, with no vapor barrier/retarder in effect to stop the condensation from the inside.


 Yes I think this will fix my problem. Ill probably repaint the siding and repair any places that could lead to leaks and I have a water proofer that I could spray on the insides of the siding. I'm going to stick with the fiberglass insulation mainly because its the cheapest option and I don't want to invest too much in such a small shed. It's more of a practice shed for me because in like 3 or 4 years I plan on building my own shed that will be much larger, so its more of a temporary insulation.


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