Waterproofing osb

Discussion in 'Carpenters' Talk' started by amarok88, Sep 22, 2019.

  1. amarok88

    amarok88 Member

    Hi guys.
    Putting 18mm osb down for my shed base as i need to do this before i can build my sides on top of it.
    Problem is weather is a bit **** and it could be a few weeks until i get roof on the shed as its big.
    What can i do to waterproof the osb so its doesnt turn to mush until shed os complete?
    I have a large tin of blackjack, should i just paint that on it?

    Please dont suggest marine ply or timber floorboards, im using osb as im poor
  2. JustPhil

    JustPhil Active Member

    Osb2 or osb3? A bit of rain might not be a problem.

    And do you really need to lay the floor down before building the structure? If the osb is a finished floor, lay it after you’ve built the shed surely...
  3. amarok88

    amarok88 Member


    I would prefer that but then i would need to cut around every upright to fit it in. Or double up the outside edges of the floor frame for the floor to sit on

    Your prob right though, it would be the best way
    Last edited: Sep 22, 2019
  4. ajohn

    ajohn Screwfix Select

    Is there that much difference in the cost of shuttering ply also used to board up windows?

    I have no idea why I did it other than thinking try it I made some garage doors out of osb. It soaked up rather a lot of paint. Water eventually got in via edges. Took a few years but it did. Neither this or ordinary plies are likely to survive all that long if any part is exposed to moisture.

    Maybe a cheap answer would be to build on a frame made up of decking around the edges but that wont last long if in contact with the ground. For timber it's cheap and pressure treated etc.

    I had a shed once. When I bought it the total cost was well under what it would have cost me to buy the timber. Maybe I was lucky price wise but all sorts of people start making sheds. If I made one and wanted to keep costs down I would probably make the entire thing other than framing out of ply and treat it with oil based perservatives.

  5. mr moose

    mr moose Screwfix Select

    Use a couple of heavy duty tarps, or how about your roof material as a temporary cover?

Share This Page