Does MDF bow and warp???

Discussion in 'Carpenters' Talk' started by paulo333, Oct 26, 2006.

  1. paulo333

    paulo333 Member


    I have been abroad for years doing other things. Now back here and resuming carpentry I find materials new to me to learn about - MDF for one. I thought this stuff was pretty much warp-proof?
    I have put up sliding doors made from 18mm MDF - dimensions 700 wide x 2200 high. They are starting to bow in the middle - like bananas - within a few days of making. No moisture sources or complications on site. Is this to be expected or is something wrong here (maybe poor quality stock from my supplier?)

    As far as a solution goes I would welcome knowledgable suggestions from old hands. I could replace the doors with ?? plywood??

    OR, I have thought to screw some of those metal shelf-support uprights to each long edge of the doors. Then glue and pin a wood cover strip to that. Looks much more elegant than it sounds - I did it before on a wide span of shelves and looks good.

    All the best and thanks. Paulo
  2. jasonb

    jasonb New Member

    The warping is probably due to an unequal temperature either side of the doors, the room side will heat up with the central heating, the wardrobe side will be cooler. If the MDF had been stored in slightly humid conditions then the heat differential will be causing the room side to dry out and contract faster than the inside. Worth leaving the doors open a bit for a week or two to see if they straighten.

    Have you applied any finish to the MDF ?, you must treat each side the same as they are not supported by any form of frame.

    There is also a question of the quality of the MDF, builders merchants and the sheds will generally carry a "contract" grade of MDF which is not as good as one by a known maker such as Caber or Medite. I make quite a lot of fitted furniture from MDF and always use Caber MR (moisture Resistant) MDF as it gives a much better machined edge.

  3. dunc

    dunc New Member

    Most mdf will be slightly bowed, unless it has been stored carefully. Because some sheets do come nice and true all round.

    When I am making doors I use 25mm frames and 6mmm panels. I choose each piece with the bow outwards. This will close against the frame and will look good.

    Also its important to paint both sides in the same session to avoid bowing.
  4. dirtydeeds

    dirtydeeds New Member

    Planofit door straightening sets. Fit them and they will take the bow and warp out.

    I put them in 8 foot MDF doors over 600 wide to stop them bowing. Expensive yes, but ive never had a call back for bowed doors.
  5. paulo333

    paulo333 Member

    Thank you. God bless you! Really.

    I hope you understand what a great support it is to have wise souls willing to generously share their expertise and knowledge. This game can be a bit daunting and lonely at times. Being part of an extended network like this is brilliant.

    Many, many thanks to you - and to all the others who support and answer so many other questions.
  6. paulo333

    paulo333 Member

    dirtydeeds: I searched on Google to find "Planofit" but nothing. Do you have any other info about this product?
  7. mr_refurb

    mr_refurb New Member

    Planofit door straightening sets from HAFELE
  8. STGO

    STGO New Member

    hey paulo,
    the most important thing to know about mdf is that the dust from it is extremely harmful, always wear a mask and never let children into the area you are working in

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