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Thread: Sealing Joints In 6 mil Polyethylene Film

  1. #1
    Join Date
    Sep 2002

    Default Sealing Joints In 6 mil Polyethylene Film

    I am having a french drain system put around the footings of my foundation to remedy a water seepage into my basement. The contractor is not very experienced and does not know what to use to seal the plastic film underlay joints and attach the film to my foundation. Any suggestions of a product or type of product would be greatly appreciated.

  2. #2


    In my opinion if you want a dry basement you should just follow the rules of the International Residential Code. Below is a copy of a perimeter drain design as you should install it per the IRC. Below is a copied section of that rule. Should be self explainatory.


    SECTION R405
    R405.1 Concrete or masonry foundations. Drains shall be
    provided around all concrete or masonry foundations that re-
    tain earth and enclose habitable or usable spaces located below
    grade. Drainage tiles, gravel or crushed stone drains,perforated
    pipe or other approved systems or materials shall be installed at
    or belowthe area to be protected and shall discharge by gravity
    or mechanical means into an approved drainage system. Gravel
    or crushed stone drains shall extend at least 1 foot (305mm)be-
    yond the outside edge of the footing and 6 inches (153 mm)
    above the top of the footing and be covered with an approved
    filter membrane material. The top of open joints of drain tiles
    shall be protected with strips of building paper, and the drain-
    age tiles or perforated pipe shall be placed on a minimum of 2
    inches (51 mm) of washed gravel or crushed rock at least one
    sieve size larger than the tile joint opening or perforation and
    coveredwith not less than 6 inches (153 mm) of the samemate-

    My comments.

    To water proof the outside of the cement basement wall also should be done meeting the rules of the IRC that apply. Should also be self explainatory.

    Copied section of the 2003 IRC below;

    R406.2 Concrete and masonry foundation waterproofing.
    In areaswhere a highwater table or other severe soil-water con-
    ditions are known to exist, exterior foundationwalls that retain
    earth and enclose habitable or usable spaces located below
    grade shall be waterproofed with a membrane extending from
    the top of the footing to the finished grade. Themembrane shall
    consist of 2-ply hot-mopped felts, 55 pound (25 kg) roll roof-
    ing, 6-mil (0.15 mm) polyvinyl chloride, 6-mil (0.15 mm)
    polyethylene or 40-mil (1 mm) polymer-modified asphalt. The
    joints in themembrane shall be lapped and sealed with an adhe-
    sive compatible with the waterproofing membrane.

    My comments.

    The black tar cold mopped on the concrete as discibed above will also seal the joints of the bisquine as long as you overlap the plastic sheeting about a foot and mop cold pitch to the back sheet then press the outer sheet tight to the inner sheet of plastic as the cold pitch is still wet. The entire concrete wall should be cold pitch mopped then the plastic installed while the cold pitch is still wet using that cold pitch as the adhesive to hold the plastic sheeting to the concrete wall and also to create an adhesive for the lapping of two sheets that over lap.

    Above where it discribes drainage remember that the intent is to keep the water out of the basement. I do not advise making a cross over pipe to drain this outside perimeter drain into the basement sump pit then pumped out of the basement. This would be contrary to your goal. I suggest you keep any inside sump pit or underfloor drainage to be separate from the required outside perimeter drain. I suggest that you go to your lumber company and buy a plastic 12' long 24" diameter driveway drain pipe. Then while you have your trench open stand that 24" pipe verticle into the trench running your perimeter drain through holes in the side of that verticle 24" diameter pipe. This will create a systern. Make sure the pipe is about a foot deeper than the lay of the perimeter drain so water from the drain will drain into that 24" verticle cycstern pipe you just installed. Install about 6" of #3 crushed stone or washed rock in the bottom of that pipe to make a floor in that cystern pipe you created. Then install a GFI protected 20 amp 120 volt receptacle. Then buy a sump pump to drop by rope into that cystern pipe to the bottom and plug into the receptacle you installed within reach inside that cystern pipe. Then connect a hose to the pumped outlet of that sump pump in a drain line 4" diameter that will run below ground to a low spot on your land where the water will continue to flow away from your house. Then install an access lid [fiberglass] so it is flush with the earth. Then you can mow over it and forget it is there but keeping water out of your basement and pumped away by that subsurface cystern style sump pump installed outside in the yard where you perimeter drain drains into. If you are concerned of not knowing this pump will stop working then install a second float switch connected to a red light in your house so if the water rises beyond the sump pump float switch due to a failure of this hidden pump the second float switch will turn on a red warning light say in your garage to tell you have sump pump failure. The waterproofed basement walls will keep out the moisture long enough for you to pump the cyctern back down to normal and install a new sump pump. Easy repair. Water kept out of the basement thus eliminating moisture inviting black mold etc. and you have a dry basement because this perimeter drain has artificially lowered the subsurface water table around your house thus eliminating your wet basement and health hazard.

    Be aware the trench around your house must be kept at least 2' away from your existing basement wall to avoid weakening the foot print of your house at the footing. The 2" of crushed stone or washed rock sized #3 or larger is supposed to be installed 6" below the top of your footer where your basement floor is located in elevation. Then the 4" perimeter drain pipe is installed all the way around the house. Then the 6" of crushed stone or washed rock sized #3 or larger is installed over that permiter 4" drain pipe then a filtering cheeze cloth is to be installed over that last 6" of crushed stone or washed rock to keep the dirt fines from washing into that stone or rock and plugging the drainage ability. Remember when you get done you should have a 12" wide by 12" tall [2" rock under pipe, 4" pipe, then 6" rock above pipe] box of drainage design.

    If you have a natural fall of finished grade to a point below the perimeter drain elevation then dig a trench level but with a minimum of a 2% fall to that point where the drainage area is located to daylight below the elevation of the drain pipe. This would be a gravity style design [much better if available] eliminating the need for the cystern sump pump as discribed above.

    If you will do it as discribed above you will have no more wet basement problems.

    If this is a new basement then install the above discribed perimeter drain and the 12" wide by 12" high boxed stone of that drainage directly beside the outside of your footing with the top of that drain pipe even with the top of your footer and with 2" of washed rock or crushed stone below it.

    Do not short sheet this make it a clean installation without any debris in this drainage design or it won't work properly.

    Hope this helps


  3. #3
    Join Date
    Sep 2002

    Default Sealing Joints In 6 mil Polyethylene Film

    Thanks so much for responding so swiftly. Unfortunately, my contractor has already excavated a trench around the two portions of my foundation that have a problem and also a trench that runs from the intersection of the two problem sides to a gravel filled dry well about 50 feet downgrade. He lined the trenches by my footings with 6 mil black polyethylene and paced about 1-2 inches of washed 2" gravel in the plastic. Then he placed 6 inch perforated pipes on top of that and connected them to a y joint connected to a solid 6" pipe that goes to the drywell. The problem is that he does not know what to use to seal the connection between the poly sheets. Thus there is no way to assure a water tight installation. He tried black bituminous sealant to attach the film to the foundation but it didn't stick very well and the sheet fell down in several places. I was hoping to find a more effective sealant/adhesive for the jobs. I should mention that the footings are about three feet above the current floor level since there originally was a crawl space in the end of the basement, that was dug out. A concrete box filled with earth serves as the interior support for the footings. Thus it is easy for water to travel below the footings and enter the basement through spawl cracks in the interior box and at the floor joint.

  4. #4


    Sorry if you don't do it right the first time then chances are you will be living with the wet basement or redoing it a second time.

    If the trench is still open then take the trenches the rest of the way around the house. Then install the perimeter drain as I spoke on my last reply.

    To short sheet here is to wich you had done it right at a later date.

    I question this dry well. Have you hired a soil scientist to find the seasonal high water table and type of soil for horizonatal perk. What makes you think that dry well is going to be dry when the rains come in that floods the basements? Water table will most likely fill your drywell stopping that drain you installed from working until the drywell dries out when you then won't need the drain.

    You are missing in your design what is needed to create your dry basement.

    Do it right the first time.

    Just my thoughts


  5. #5
    Join Date
    Sep 2002

    Default Sealing Joints In 6 mil Polyethylene Sheeets

    Hi, I hired an archetect engineering firm to design my drain. We live in the high desert here. Rarely get 7 inches of rain per year. We do occasionally get enough snow to stand 6-12 inches deep on the ground and on roofs. A quick thaw can lead to trouble. My main source of water is irrigation. The last incedent was a 1-1/4 inch irrigaion pipe that split while I was away on my honeymoon. That water damaged my foundation and made a mess. Today my contractor found a urethane caulk that stuck the sheets to the foundation and also used it to seal between layers of the sheets. We are testing the seals tonight. We ran full force water from a hose bib into the trench for 40 minutes and tomorrow I will look for water penetrating the foundation. Hope I don't find any.
    Thanks for your interest in this project. I found that it is so rare in this area of eastern Washington State that there were no excavation contractors that were willing to undertake the job. What a contrast with the Seattle area where water problems are very common.

  6. #6


    Good Luck with your project. After the rainy or spring thaw and tell us how you experience your project then.

    Good Luck


  7. #7
    Join Date
    Sep 2002

    Default Sealing Joints In 6 mil Polyethylene Film

    I got bad news the night we tested the urethane foam sealant. Joints leaked like sieves. Contractor had to reexcavate the entire system and use a single sheet with no joints and with at least a 5 foot path length of compacted soil between the downgrade edge of the film and the foundation. That tested ok. I'm still curious about what sealants are good for those sheets. My guess from automotive and motor home seals is Butyl rubber caulk. It is the stickiest stuff I have used.

  8. #8


    The sheets are not water proof protection nor is the sealant you put on the walls. They are only intended as a retardant to repel water long enough for the perimeter drain to lower the subsurface water table as I explained in my first reply. The key method of the entire design is the properly installed perimeter drain that lowers the subsurface water table away from the basement so there is not water to leak into the basement due to subsurface water that is no longer there.

    Same technique is used with septic systems. Only difference is location of perimeter drain. Basement right next to footer below the footer. Septic 10' away from finger system surrounding the finger system. It is expected that 10' of proper earth will filter the water to safe levels to allow subsurface water to drain away from system.

    Reason basements are wet and septic systems won't work most commonly is due to high subsurface water table. Lower the subsurface water table and both will operate properly with dry basement and active successful septic. The two products must have their own perimeter drains but principle is mostly same. Lower subsurface water table in that relating area you are trying to use those products.

    Plastic sheeting and coating of basement walls are a help to allow the subsurface perimeter drain to have time to do its job. Short cut that design and you will have less than positive results of your goal.

    Just my opinion


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