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Plastic Sheeting for a Crawlspace- What's best?

Posted by Nana Hinsley on Wed, Mar 30, 2011 @ 01:32

Question.: There are so many different vapor barriers (vapor retarders) to chose from. How do I know which one to buy and use? What's the best material for a crawlspace?

Answer.: TRUTH 1: No two water vapor retarders are created equal. The vapor retarder you select should be manufactured from high-grade raw materials that are consistent in quality, unlike common construction grades of 4, 6 or 10 mil polyethylene. Construction grade films (known as C&A or visqueen) are typically produced with very low grades of polyethylene resin and a very high percentage of "post consumer" recycled materials. The numerous heat cycles that occur in reprocessing of recycled materials, combined with the varied types of resin used, cause inconsistencies in physical strength and permeability. While this commodity film serves a purpose in temporary construction and agricultural applications, it is not designed to provide ongoing protection against unwanted moisture. Film characteristics such as low strength and poor resistance to decay should be of major concern.

TRUTH 2: A long-term vapor retarder must maintain life long integrity by resisting decay, attack by moisture, organisms in the soil and chemicals. As mentioned above, beware of vapor retarders manufactured with "post consumer" recycled resins (C&A Poly or Visqueen) which can degrade from chemicals in the soil. Paper laminates can degrade from moisture attack.

TRUTH 3: Moisture problems associated with a vapor retarder installed under the concrete slab-on-grade are often traced to punctured or torn water vapor retarders. Damage due to construction traffic during installation, can be detrimental to the performance of the vapor retarder. Physical characteristics such as high puncture resistance and tensile strength, along with low-moisture vapor permeability, are vital attributes of a vapor retarder. These physical characteristics are well quantified in ASTM E-1745 and are outlined in this guide.

TRUTH 4: When specifying a water vapor retarder, designed for use in under concrete slab applications, insist the supplier meets the newest and most stringent ASTM standard, ASTM E-1745 for "Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs". It assures minimum values are met regarding tensile strength and puncture resistance, along with the maximum allowable water vapor permeance. ASTM E-1745 separates these properties into three performance classes: Class A, B & C.

Tags: Best crawlspace plastic

LLDPE- the most flexible plastic sheeting films

Posted by Nana Hinsley on Tue, Mar 15, 2011 @ 01:49

Is LLDPE the most flexible of the plastic sheeting films?

Answer: Linear Low Density Polyethylene (LLDPE) is the most flexible of the plastic sheeting films. LLDPE is blended form of LDPE where the film has much more flexibility, tensile strength, and more conformability. It is more pliable and softer. LLDPE is used for pond liners or blended into other films to give them more flexibility and extra strength. LLDPE is used for films that need a tremendous amount of strength to absorb impacts while not tearing or puncturing. An example of this is a carpet plastic film that adheres to the carpet. It is strong enough to withstand foot traffic, even from stiletto high heels! The molecules all line up and strongly hold together as the film is stretched. The most common thickness range is from 0.5 mil to 40 mil in flexible plastic sheeting.

Tags: LLDPE, carpet plastic

Vapor Barrier On Top Of Concrete, Below Carpet

Posted by Nana Hinsley on Tue, Mar 01, 2011 @ 10:27

QUESTION: We are looking for a product that can be laid on a concrete slab to act as a vapor barrier between the concrete and the carpet we plan to put in our basement.

Do you have a product that might work for this? 

Do you know if there are any contra-indications to putting the vapor barrier on TOP of the concrete to separate it from the carpet pad. It seems your products are used mostly between the ground and the concrete slab.

ANSWER: Any of our Vapor Barrier types of products can be used in this application over the concrete slab. I would recommend Raven Industries VaporBlock 20 Plus or the VaporBlock Plus 6 as two of the better ones, since they also block out radon, methane, and VOC's. Ideally, the liner should be sealed to the concrete floor using tape, or non-hardening polyurethane caulking, as close to the outside walls as possible. The idea is to help direct any moisture that flows along the plane under the concrete to the outside walls, so it can dissipate to the outdoors if possible. If this is not possible, and any moisture will be going into interior walls, they may want to stop a couple of inches short of the walls to keep from directing moisture up into the interiors of walls. I give the VaporBlock 20 Plus my highest recommendation, even though it is more costly. I believe it is such a superior product over all the others, that it is worth the difference. For this application, I would probably make the VaporBlock 6 Plus my next highest, even though it is pretty thin. It still has the very tight cell structure, and could be doubled it if you wish. Crawlspace 1800 is also a good choice.

Tags: Crawlspace 1800, vapor barrier on top of concrete