# moisture behind vapour barrier



## piperboy (Jul 24, 2006)

Hi
On the weekend we noticed we had moisture behind the vapour barrier along the whole back wall and part of 1 side wall of our basement. There are no studs, just the cement foundation, the long roll type insulation and the plastic barrier strating about 4 feet above the floor. Our house is 3 years old, we have always had a dehumidifier in the basement, we live 2hrs from Detroit - and we have had the A/C on a lot (but no different than previous years). The only difference is that we recently had a concrete patio outside poured July 5th along the whole back wall of our house. Does anyone know what would have caused this? Is it related to the patio we had poured out back? Any suggestions?
Thanks


----------



## AaronB (Jan 29, 2005)

leaky foundation?


----------



## ron schenker (Jan 15, 2006)

Check to see that the concrete patio is sloping away from the house directing rain water towards the yard and not towards the foundation wall.


----------



## manhattan42 (Jun 4, 2006)

*Normal*



piperboy said:


> Hi
> On the weekend we noticed we had moisture behind the vapour barrier along the whole back wall and part of 1 side wall of our basement. There are no studs, just the cement foundation, the long roll type insulation and the plastic barrier strating about 4 feet above the floor. Our house is 3 years old, we have always had a dehumidifier in the basement, we live 2hrs from Detroit - and we have had the A/C on a lot (but no different than previous years). The only difference is that we recently had a concrete patio outside poured July 5th along the whole back wall of our house. Does anyone know what would have caused this? Is it related to the patio we had poured out back? Any suggestions?
> Thanks


Sounds normal.

If you are dehumidifying your basement, you will be drawing in ground water vapor through the soil into you basement.

Even if you have a vapor barrier on the concrete foundation walls, you will see some of this ground water vapor condensing upon the basement vapor barrier.

As long as you run your AC and as long as you run your dehumidifier you will cause the water vapor diffusion differential to flow _*into*_ the basement from the normally wetter ground soil.

This will cause your basement to be wetter when you run the AC and dehumidifier than when you do not.


----------



## piperboy (Jul 24, 2006)

*Thanks - still have some questions*



manhattan42 said:


> Sounds normal.
> 
> If you are dehumidifying your basement, you will be drawing in ground water vapor through the soil into you basement.
> 
> ...


Thanks Manhattan42 and everyone else!
We still don't understand that it is the wall we had the patio poured and no other wall. Our backyard is in full sun all afternoon and night and the new patio gets pretty hot during the day. The patio does slope away from the house. We will stop using the dehumidifier. Any suggestions as to why it is only one wall of the basement?
Thanks Again.


----------



## KUIPORNG (Jan 11, 2006)

I would cut the insulation out and have a look at the concrete wall... It is not that difficult, in fact, I cut all mine out in my basement to reinstall, as what you have is not properly done... there should be a layer of somthing between the insulation and the concrete wall which you properly didn't have.... You may have a leak on the wall... if this is the case, you want to fix it... May be your pouring concrete patio affect the underground water distribution making it more easy to go into your basement.. or may be it just conincident that your wall start to leak at the same time with your pouring concrete which has no relationship of each other.... may be... 

you got to look at the concrete behind the insulation to know for certain...especially after heavy rainfall..


----------



## manhattan42 (Jun 4, 2006)

Thanks Manhattan42 and everyone else!


> We still don't understand that it is the wall we had the patio poured and no other wall. Our backyard is in full sun all afternoon and night and the new patio gets pretty hot during the day. The patio does slope away from the house. We will stop using the dehumidifier. Any suggestions as to why it is only one wall of the basement?
> Thanks Again.


Too many potential variations to give any further helpful advice.

If the weather has been more rainy than normal in your region and the ground slopes downward toward your patio...it may account for the problem...

Your underground geology could affect one wall being wet and all others dry...

Badly spaced spouts can also account for the issues.

The placing of your basement wall's vapor barriers is very unusual and may be contributing to the problem....

Wrapped insulation placed directly against a concrete foundation is always bad news...

Would need more detailed information to wager a guess...


----------



## Rockit (Sep 5, 2008)

Piperboy, did you ever find the culprit to your problem. We are having the exact same problem in our basement. Live one hour from Toronto. Just put a interlocking deck in the backyard right up against the back wall. The deck gets most of the sun during the day. Builder put insulation directly against concrete wall starting about half way up. Used vapour barrier to hold insulation against wall. Vapour barrier in not "air tight". So I have two theories...warm air hit cold concrete wall and condensed on the warm side of the barrier. Or ground underneath new deck is warmer and wetter than before and moisture is forced in to the houes (in the form of water vapour) and is condesing on the vapour barrier.


----------



## Maintenance 6 (Feb 26, 2008)

I would venture a guess and say that ground moisture along this wall used to be able to travel to the surface and evaporate. It can't do that anymore because you've trapped it under a concrete patio, so it's showing up behind your plastic.


----------



## orange (Feb 19, 2008)

Rockit said:


> Piperboy, did you ever find the culprit to your problem. We are having the exact same problem in our basement. Live one hour from Toronto. Just put a interlocking deck in the backyard right up against the back wall. The deck gets most of the sun during the day. Builder put insulation directly against concrete wall starting about half way up. Used vapour barrier to hold insulation against wall. Vapour barrier in not "air tight". So I have two theories...warm air hit cold concrete wall and condensed on the warm side of the barrier. Or ground underneath new deck is warmer and wetter than before and moisture is forced in to the houes (in the form of water vapour) and is condesing on the vapour barrier.


Piperboy-- Did you ever solve the problem? If so, what did you do?


----------

