Drylok and Vapor Barrier?


Old 01-11-05, 06:28 AM
Visiting Guest
Posts: n/a
Drylok and Vapor Barrier?

I am planning on refinishing my basement and trying to decide if I should put Drylok on the basement walls. I have never seen water in the basement or any wet spots on the walls but for added protection I was thinking of waterproofing with drylock before I put up the framing. The framing will be 2x4 with kraft faced insulation (facing towards inside). Then 1/2" sheetrock. It only recently occurred to me that I might be creating a double vapor barrier situation between the Dryloked walls and the kraft facing, is this true? Would this be a problem?

Thanks for any thoughts,
Sponsored Links
Old 01-11-05, 06:51 AM
majakdragon's Avatar
Join Date: Jul 2003
Location: N.E. Arkansas
Posts: 7,827
Received 0 Votes on 0 Posts
My opinion is that Dry-loc would actually be no different than a poured concrete wall. If you are in doubt, I would check the Dry-loc bag and contact them for an expert reply. They probably even have a website. Good luck with your project.
Old 01-12-05, 07:10 AM
Visiting Guest
Posts: n/a
Jumping in to add a question...................
My walls are 4 year old poured concrete (seemingly dry) do I need to Drylok the walls prior to building 2x4 walls?

Also if I Drylok, do I need to etch the walls first? Could someone recommend a product that is not as dangerous / smelly as muratic acid?

Old 01-12-05, 04:06 PM
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: USA
Posts: 1,875
Received 0 Votes on 0 Posts
Vapor barriers or water proofing products do not stop moisure flow, they both slow it down. All materials will absorb and expel moisture. Example, all materials have a "Perm Rating". This is a standard rating system that describes the rate of moisture permability of the material. A Vapor Barrier material must have a Perm Rating of 1 or less.

Drylok and similar products do not have a Perm Rating of 1 or less but can depending on how thick it is applied. Drylok is a moisture barrier and not a vapor barrier. This is because moisture molecules in a liquid state are more compacted together than in a vapor state. Drylok addresses the liquid state of moisture and not the vapor state.

Another way to distinguish between the two is Drylok and similar products prohibit liquid water penetration and Vapor Barriers reduce or retards moisture flow inside heat to prevent condensing of the moisture in the heat. Psychrometrics in Physics is the term that describes this behavior but what most people are familar with is Relative Humidity (RH%).

There are several facts with this application that must be considered.

1. All materials absorb and expel moisture. In fact, most materials start out moist and must retain moisture in order to be stable. Too much or too little moisture and the material destabilizes. Which usually results in structural failure.

2. Sources of moisture on a structure is generated inside and outside the structure. Structural failure usually has outside generated moisture associated with it and Poor Indoor Air Quality usually has inside generated moisture associated with it.

3. The design feature most structures use to deal with moisture is known as a Water Shedding System. Roofing shingles, siding materials, Drip edges and caps are all Water Shedding Systems. For basements, you have Site Grading as its first defense and masonry as its second defense. For example. a good grade around the perimeter of the basement sheds the majority of water away from the basement. Since the ground has a higher Perm Rating than the masonry, it should absorb and expel the moisture in it before the masonry has time to.

4. Below grade applications are affected more by Capilliary Action (suction) than above grade applications.

I would not recommend basement water proofing to a basement that is apparently dry. It indicates good Site Grading, soil and roof drainage system. Furthermore, it indicates that the masonry in the basement is a major source for the removal of moisture generated inside the structure. Equilibrium Relative Humidity(ErH%) states that an object of lower humidity will absorb humidity from objects of higher humidity until the humidity levels are equal. Basement water proofing applied to basement walls reduces the ability of the masonry to absorb the moisture generated inside the basement. It is good to note that it does not stop moisture flow, it slows it down.

In other words, applying Drylok to an apparent dry basement wall is not a preventive measure, in fact I would consider it to be increasing the probability of an Indoor Air Quality problem.

Since vapor barriers are applied only to insulation and deals primarily with the prevention of the moisture in heat from condensing as the heat loses temperature, it will have little affect on ErH% and the ability of the masonry walls from absorbing the moisture generated inside the basement.
Old 01-13-05, 02:50 PM
Visiting Guest
Posts: n/a
Very interesting read. Basically you are saying NOT to seal the walls because a dry basement is actually losing moisture through the walls to the outside? Lower moisture inside basement = less chance for mold/mildew/smell/etc...

I think I understand that you don't want condensation to form on the insulation when the warm air cools, thus the vapor barrier between the drywall and insulation. But, doesn't a vapor barrier also retard the moisure from leaving the basement? I understand that dryock retards water in liquid state and not vapor state, but a vapor barrier retards both, no!?

ANYWAY, I have already applied drylock to 2 walls and studded them. The studs are very close to the wall. I was then going to insulate, vapor barrier and drywall. Bad news?
Old 01-13-05, 06:19 PM
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: USA
Posts: 1,875
Received 0 Votes on 0 Posts
Vapor barriers retard moisture flow in heat but has little or no effect on Equilibrium Relative Humidity (ErH%).

When Dryloc or any other basement water proofing is applied the most logical thing to do is control the sources of moisture in the basement. For example, if a dryer is used in the basement, make sure it exhaust properly to the outside. Cooking and Showering must have exhaust fans to the outside. Plumbing should be checked periodically for leaks. Humans give off about 2 pounds of humidity a day, a dog gives off five pounds. So don't leave the dog in the basement all day if you have one. Better off leaving him upstairs.

You can go to the EPA.gov website on Indoor Air Quality and they have some more tips on how to control moisture in the home to prevent mold and mildew growth.
Old 01-14-05, 05:59 PM
Visiting Guest
Posts: n/a
Well, no dryer, dog, bathroom in the basement, so that's a godo start. I'll run a dehumidifer down there as well.

Thank you again for your help!
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: