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  • How to seal a basement wall prior to finishing

    I'd like to finish my basement, and want to do it right. I've been hearing conflicting information regarding how to treat the basement walls prior to putting up the studs and drywall, and am looking for some solid advice. A few facts:
    - cement block basement walls
    - currently have white "blanket" insulation
    - water problem on a 16' and a 24' length (2 sides)
    - dry during summer, but moist/weeping in fall & spring
    - land is graded away from foundation
    - downspouts far away from foundation
    - 24' wall faces weather, so that side gets more wind-driven rain
    - floating slab basement floor
    - sump pump will be in the finished area, but enclosed in a closet

    My general plan is to remove the blanket, clean the walls, dry them, and put on some DryLoc. Then staple a sheet of plastic on the top sill plate and run it down to the space between the floating slab and the wall. I was planning on using steel studs (on recommendation from a remodeler friend) with ordinary 16" fiberglass batts, no moisture barrier.

    For the sump pump closet (basically a shallow rectangular room with pantry doors) I plan on using greenboard.

    Does this sound like a good plan? I'd like to make sure it is right the first time. Thanks.

  • #2
    Re: How to seal a basement wall prior to finishing

    Greenboard is junk...

    I would recomend a paperless drywall product in places where you suspect moisture.

    Of course you want to solve the bulk moisture problems before installing any of them.

    Densarmor and Denshield are the ones i'm familar with.

    They cost more, but with no paper, it's very tough to have them mold.

    Comment


    • #3
      Re: How to seal a basement wall prior to finishing

      Originally posted by radar_40 View Post
      Greenboard is junk...

      I would recomend a paperless drywall product in places where you suspect moisture.

      Of course you want to solve the bulk moisture problems before installing any of them.

      Densarmor and Denshield are the ones i'm familar with.

      They cost more, but with no paper, it's very tough to have them mold.
      Good advice, thanks.

      Any input on the wall sealing?

      Comment


      • #4
        Re: How to seal a basement wall prior to finishing

        First you need to determine if your water issue is seepage through the block or just interior airborne moisture condensing on the cold block. You can tape off a 2' square with 6mm vapour barrier and tuc tape, if the area stays dry and the rest of the wall is wet then it is just interior moisture, if water starts to bead under the plastic then you need to fix the problem from the outside. There is all kinds of crap on the market to waterproof a wall from the inside but all you are doing is masking a problem and setting yourself up for issues down the road. If you seal the interior wall you are trapping the moisture in the block and they will eventually degrade. If you end up digging seal the wall with a good rubberized product and use a dimpled membrane down to the weepers, if the weepers are old or have no filter socks then dig them up as well and put in new big O with the sock and cover with clear stone. Now for the basement. Use the same dimpled membrane on the floor and tape the seams with tuck tape, lay sheets of 5/8 T&G chip on top of the membrane and glue the joints with PL premium (this is the same as using the Dircore product but less than 1/2 the price and better IMO. For the walls you can either use glued shiplap extruded polystyrene or have someone come in and spray it in the expanding product. If you go with the spray in build your walls so they are about 1.5" off the block wall (install the floor with the same gap - use a 2X4 on edge to help maintain the gap and it give you a support to allow you to pound your T&G together). You will now have a basement that will be dry and feel like any other room in your house.
        Last edited by wbrooks; 11-02-2010, 08:37 AM.

        Comment


        • #5
          Re: How to seal a basement wall prior to finishing

          Originally posted by wbrooks View Post
          Now for the basement. Use the same dimpled membrane on the floor and tape the seams with tuck tape, lay sheets of 5/8 T&G chip on top of the membrane and glue the joints with PL premium (this is the same as using the Dircore product but less than 1/2 the price and better IMO.
          I have a sump pump. If this fails, or I get water in the basement from a busted water heater, then the subflooring you suggested would be ruined and would need to be replaced, wouldn't it?

          Comment


          • #6
            Re: How to seal a basement wall prior to finishing

            Your sump should have an alarm and a backup if you intend to be away a lot. The suggested floor provides a 1/2" air gap before the wood so even on a 600 sq ft basement you need 187 gallons to get beyond the 1/2" mark (depending on basement slope) and you would need really bad luck to have you water heater and your sump die at the same time. My utility room is near my pit and is left as bare concrete as there is no need for floor comfort in this room. This type of floor offers a good deal of protection and with the air gap, it allows seepage to dry without allowing dampness to feed mold.

            Comment


            • #7
              Re: How to seal a basement wall prior to finishing

              not bashing your friend but the man from Canada is right...if you want a problem free basement...its time to dig your foundation up spray and wrap, check the weepers/replace then atleast 5 feet of 3/4clear stone...for the inside i would personaly not use steel if there is a moisture problem i find steel rusts alot faster than wood rots...u can also use a poly on your floor strap the floor with 2by4's on 16's and use a foam to insulate the floor and use 3/4 t&g sheathing spray the walls if u fix the foundation.

              Comment


              • #8
                Re: How to seal a basement wall prior to finishing

                for the quick fix before getting to doing the outside like others have said, google a product called Xypex Concentrate it is the best product I have used.
                And no plastic barrier near the wall it won't breath.
                Seattle Drain Service

                Comment


                • #9
                  Re: How to seal a basement wall prior to finishing

                  Originally posted by Cuda View Post
                  for the quick fix before getting to doing the outside like others have said, google a product called Xypex Concentrate it is the best product I have used.
                  And no plastic barrier near the wall it won't breath.
                  backwards tyvek against the foundation wall works well for basements.

                  Comment


                  • #10
                    Re: How to seal a basement wall prior to finishing

                    Originally posted by JoePolvino View Post
                    Does this sound like a good plan? I'd like to make sure it is right the first time. Thanks.
                    you will find what you need here: http://www.buildingscience.com/searc...eText=basement.

                    find right pdf documents and read them. you will know which way you should go.

                    Comment


                    • #11
                      Re: How to seal a basement wall prior to finishing

                      Originally posted by wbrooks View Post
                      First you need to determine if your water issue is seepage through the block or just interior airborne moisture condensing on the cold block. You can tape off a 2' square with 6mm vapour barrier and tuc tape, if the area stays dry and the rest of the wall is wet then it is just interior moisture, if water starts to bead under the plastic then you need to fix the problem from the outside. There is all kinds of crap on the market to waterproof a wall from the inside but all you are doing is masking a problem and setting yourself up for issues down the road. If you seal the interior wall you are trapping the moisture in the block and they will eventually degrade. If you end up digging seal the wall with a good rubberized product and use a dimpled membrane down to the weepers, if the weepers are old or have no filter socks then dig them up as well and put in new big O with the sock and cover with clear stone. Now for the basement. Use the same dimpled membrane on the floor and tape the seams with tuck tape, lay sheets of 5/8 T&G chip on top of the membrane and glue the joints with PL premium (this is the same as using the Dircore product but less than 1/2 the price and better IMO. For the walls you can either use glued shiplap extruded polystyrene or have someone come in and spray it in the expanding product. If you go with the spray in build your walls so they are about 1.5" off the block wall (install the floor with the same gap - use a 2X4 on edge to help maintain the gap and it give you a support to allow you to pound your T&G together). You will now have a basement that will be dry and feel like any other room in your house.
                      the house we bought had the walls coated by the previous owner with water proofing, then he painted them.

                      i knew the lower row of blocks had water in them. under the floor is a tile that runs the whole perimeter then empties into a sump pump.

                      what i did was i drilled a 5/8" hole into the base of the blocks ate 6 feet intervals, then drilled a 5/8" hole into the floor and into the stone base under it. i then made several "L" shaped pipes out of copper and inserted them into the blocks and into the floor. then, i covered them with mortar.

                      this drains the bottom row of blocks in the spring when the water is the worst so that no water sits in the blocks any more. it drains into the floor then into the tile and into the sump pump. ( i tested this with colored dye)

                      it was my cheap way of fixing the problem without digging up the whole yard.

                      Comment


                      • #12
                        Re: How to seal a basement wall prior to finishing

                        Wow.

                        Please do NOT put poly up against your block wall.

                        Do NOT worry about what type of drywall to use, WHEN you take care of the moisture problem, there is no chance of mold ever growing.

                        The ground against your foundation wall will always be at 100% humidity, even in arid climates. Your block wall needs to be able to dry to the inside of the building if it ever gets wet.

                        This is where the level of vapor permeance of the materials you choose come into play.



                        Here is some food for thought.

                        http://www.buildingscience.com/docum...-analysis/view

                        Comment


                        • #13
                          Re: How to seal a basement wall prior to finishing

                          another thing for consideration is to install a water powered backup sump pump in case your normal sump fails or the power goes out.

                          http://www.basepump.com/Basepump.htm

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