Moisture continued

Thanks for explaining the issue with the Thermal Bridge. Do you feel the following would be sufficient to solve it.

1) Waterproof floor with either epoxy paint or dry lock, I am not sure which is better.

2) Add a layer of 6 mil ploy plastic.

3) Add a layer of roofing felt on top, overlapping the gaps by 8 inches.

4) Add the sleeper and insulation on top of that with a plywood floor.

5) On top of that would be padding and carpet.

If it is still humid I would add a de-humidifier or air-conditioner.

What you are saying is very useful information and I appreciate the help. I read the above in a magazine which someone recommended to solve the same problem.

 

The source of the moisture is heat transported and not pressure (capilliary action) induced. What that means is the moisture is coming from the heat in the room and not from the ground. You do not have to use either DryLock or any other moisture barrier over the slab. In fact you are better off not doing so. The slab has an absorption rate towards moisture, so the small amount of heat transported moisture that manages to get through the insulation will be absorbed by the slab and dissipated into the ground. If you DryLock or apply a moisture barrier to the slab, then you will trap the moisture between the insulation and the slab.

You would apply a moisture barrier if the source of the moisture from the slab. In your situation, the source if from the heat in the room.

 

Ok, but how should I solve the problem? I thought it could not hurt to do that as I see many people using these items in basements. What you are saying seems to indicate that it could hurt. I am also unsure (if I did this), how the moisture would be trapped between the insulation and the slab. Wouldn't it stay within the slab? I was hoping it would not be able to come to the surface thru the paint or dry lock.

 

Also, as this room is finished I do want to put carpet over the slab. So I am looking for some solution which would allow me to do this. From what you are saying a dehumidifier or air conditioner may solve the problem. I don't want to create a bigger problem than what I have, but I thought following the steps I layed out, would ensure the problem never comes back.

 

Your moisture problem if different than most basements, first of all the slab is not below grade or water table. Below your slab you have what is known as a capilliary break, namely gravel. So the water in the ground is less likely to permeate the slab from underneath. The gravel is also known as a drainage plane. In other words, by design it does not hold water well. Though this also applies to basements, the floors of basements are usually below the water table. So the source of moisture is not from the slab or ground, it is from dew point being reached in your carpet or padding.

The dehumidifier or air-conditioner will not solve your problem because it does not address the source of the problem. Which is thermal bridging, the carpet and padding.

All materials absorb and expel moisture, regardless if it is steel, wood, carpet or insulation. What this explicitly implies is that materials can add or extract moisture from it surroundings depending on the amount and rates of absorption and expulsion of moisture of the materials involved. What this means is the slab has a high probability to extract moisture from the room in your application and not add to it. If you apply a moisture barrier over the slab, you prohibit its ability to extract moisture from the room.

If the moisture was coming up through the slab, you would have noticed a moisture problem before you finished the room. Though many of the principles apply to both basements and slabs, there is a clear difference where the moisture is most likely to come from in each area. Associating problems in basements to an above grade room is like comparing apples to oranges, they are not the same.

 

Thanks for all your help, but I am a little confused. If I add the poly plastic, sleepers and insulation, are you saying the epoxy paint would be overkill or detrimental. I definitely want to put the carpet back and don't want to make the problem worse. I was worried about the mold problem with a pregnant wife and wanted to ensure there would not be a reoccurrance of the problem once we put the solution in place. You mentioned that this would keep the moisture in the slab or between the slab and insulation, would this be a problem? I understand that you are saying if I do this and the moisture problem is caused by thermal bridging the moisture could not be absorbed back into the slab. But I am not clear if I implement the solution I describe above would I solve the problem or not.

I did a lot of research on the Internet but I can't seem to find out exactly how to solve my particular problem. I have read so many alternatives, that I decided to combine a couple together to be the best of what I thought was the best of all worlds.

Again this information has been invaluable. Thanks.

 

The web provides people with an enormous amount of information. Besides the fact that most people have different opinions on the same subject, you throw in manufacturers actually commissioning people to write articles to promote their products and all you get is a lot of misinformation or at least misleading.

To understand what occurs in your home is to realize two things, one is the best way to describe nature is balance and the other is for every action, there is a reaction. Another way of saying this is that architects primary responsibility is to bring materials together to create a structure that can withstand the forces applied to it which processes mimic nature. It is when we do things in our homes that create inbalances that produce adverse effects, such as mold, mildew and/or structual damage.

There will be times when the slab will actualy add moisture to the home and times when it will extract moisture. For example, if the humidity level in the air in the home is higher than the slab, the slab will absorb the humidity until the humidity levels in the slab and home are equal and vice-versa. This is a natural process, which is good.

But let's say there is no gravel under the slab and through capilliary action moisture rises up through the slab into the home. So much so that the home cannot equalize with it and an inbalance is created. A moisture barrier is applied over the slab to prevent the inbalance and create a condition that is more balanced in the home.

People are very fond of taking preventive measure just in case. It is true that the application of the moisture barrier you intend to install has a very low probability to create an inbalance but without the moisture barrier the probability is even less, simply because it mimics nature better.

For me to agree to the installation of a moisture barrier in this situation there must be other factors present to sway me. Such as a damp slab prior to finishing the room, wind pressure, area climatic conditions like a high humidity area, soil characteristics and drainage. Just in case, for me, is considered an inappropriate reason for the installation of the moisture barrier.

In your case I would recommend that you install the sleepers, insulation, plywood, padding and carpet. You could apply the moisture barrier if you wanted to, but what you have described, in my opinion it is not necessary.

 

resercon.. i have been reading your messages with great interest..


we are 90pct done building a home at the beach in new york.

prior to starting the contruction, i asked the builder , should we take measures (other then tar) to protect against water in the basement (10ft celing height). after pouring the foundation, he said that its a waste of money as the soil is very/very sandy. so we went with just the tar.

in april and may this year during the monsoon rains we had, not a drop of water in the basement

in july and aug, we have had little rain , but now there are some small puddles in various corners and where the floor/walls meet.

when the weather in aug was somewhat dryer (less humid), and the builder opened the windows, the water was gone, but as soon as the humitity came back, so did the small puddles.

the builder had some of his aluminum ladders on the floor in the middle of the room, and when u ran your hand over them, your hand is wet.

it would appear tobe condensation.

the outside soil is landscaped away from the foundation, and there is decking that extends 16ft away from the house, and with the sandy soil i don't think (or should i say i 'hope') that the water is coming in thru the walls.

my question/s -

the house will be finished within end sept/early oct. thereafter this winter, we will want to finish the basement.

what should the builder or we do about this. i am really at a loss as to who's problem this is. the builder should be giving me a house that has no water problems, but if its condensation , i'm not sure what steps he can take.

the last thing i want to do is 'mask' the problem with wall/floor sealants/etc.

the basement will have heat and air conditioning installed during the construction, but we certainly don;t want to finish this room, and find water afterwards.

your thoughts

thanks
ron

 

Sandy soil is by far the best drainage soil to have around your home, however, it is the most unstable soil to build on. Architects take extraordinary steps to prevent settling when building on sandy soil.

Ask you builder this, "Is it true that it takes a considerable amount of time for cement to cure and part of this process is the expelling of moisture from the cement? Is it also true that the longer cement cures, the stronger the cement becomes? Does stronger cement mean decreasing the probability that cracks may form in the cement walls and floor?" These questions are designed to put your builder on his guard. He'll think twice before answering any more of your questions.

You are correct that the puddles and wet ladders are a result of condensation. The source of the moisture is the curing of the cement in the basement. The opening of the basement windows allowed the outside air to circulate in the basement and absorb the moisture the cement was expelling by a process known as Equilibrium Relative Humidity (ErH%).

The question I would like you to ask yourself is, What affect does finishing the basement, heating and cooling the basement, which will probabily mean you will keep your basement windows close in relations to the continued curing of the cement and ErH% have?

So you want my thoughts, instead I am going to give you some advice and I hope you take it. Do not finish the basement for at least a year after completion of construction. There are two compelling reasons for my advice. One is you want the cement to properly cure. The other is there is only one other soil type that is more unstable than sand, that is landfill. The probability for settling is high. The sooner you identify a problem with settling, the less it is going to cost you to fix. Chances are if it does occur, it will happen in the first year or at least show signs that a problem exists. Then finish your basement after the year if no signs of a problem exist.

As far as your deck is concerned. More basement have water problems in them because of decks than you can shake a stick at. The reason for this is the deck kills any vegetation under the deck and the rain washes away the soil. Usually creating depressions in the soil that act as reservoirs for water. It is the reservoirs that allow water to migrate into the basement. The solution here is to apply some type of landscaping material to the soil under the deck that will prohibit the soil from being washed away when it rains.

 

Thanks for all your help and you seem extremely knowledgeable in this area. One additional information point which I am not sure I mentioned, was that the slab was painted a few times prior to the purchase of the house. I am not sure what type of paint was used and the last time must be about 5 years ago. Would this have any affect on the solution you suggested?

In this case would it be better to seal the current painted slab and proceed with the plan you mentioned.

I apologize for asking so many questions, but as you know when you finish a job and then have to take it apart and redo part of it, that could be extremely time consuming and costly.

 

The previous painting of the slab will have little effect on your application even though more than likely these paints qualified as moisture barriers. Covering the slab with an additional moisture barrier is not necessary in my opinion.

 

resercon.. thanks for your very helpful replies. we have decided to wait till next spring before commencing with the finishing of the basement.

just to show you how 'weird' my situation is

the last time we were at the house was aug 24th - the previous 4 days were basic ny summer days high in the low to mid 80's, humidity rising a little bit each day, but no rain.

when i went into the basement, there were a few small areas that had small puddles, all which were where the floor meets the walls.

we went again last friday- the previous 4 days were rainy, with 2 of the days having extremely heavy rains

1st thing, i go to the basement and would have bet money that there would be water... guess what .. dry as a bone...
very strange indeed...

ron