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We recently acquired a children's castle that was custom made originally. It seems to be completely made of MDF. The stairs are only held together by nails and they are coming apart in certain sections (top left & bottom right).

I tried pushing it back together and driving the nails back in, but it slides back out on its own over time.

staircase photo 1

What options do I have to repair this?

Here are some of my initial approaches I was thinking about:

  1. Wood glue and #8 deck screws but I'm not sure how well that will hold on painted MDF
  2. Create "bridge" underneath the top and bottom with 2x4's. Then screw from the outside into the frame with some large washers to ensure the screw doesn't pass right through
  3. Use metal "L" brackets underneath each problem step

gaps

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  • You don't really show where it is coming apart, and how. But, in general, nails are terrible for use with composites. This was always intended to be a temporary construction. Maybe edit this so the picture is inline, and add one that shows the detail of what you want to fix.
    – jdv
    May 4 at 23:08
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    Certainly not "deck" screws, as those are intended to clamp wood together. MDF fasteners will have deeper, coarser threads all the way up the shank than fasteners intended for wood.
    – jdv
    May 4 at 23:09
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    I'm completely at a loss as to how anyone would assemble this with nails alone. Nails and glue? Certainly, but nails only?? Destined to loosen or actually fall apart in time (with potentially disastrous consequences of course).
    – Graphus
    May 5 at 6:15
  • So to your 1, 2 and 3... yes, yes and yes. All of these are viable options if executed properly (which for example means pre-drilling for the deck screws, whether they are self-tapping or not). You could, and arguably should if you really want to be sure it'll be sturdy, combine 1 with either 2 or 3. Oh and welcome to Wooworking since we all forgot to say this before!
    – Graphus
    May 5 at 6:22
  • I would go with #2. 2x material under the front & back of each tread (directly under the riser at the back), with pan head screws, possibly with washers, would be the way to go. MDF is not known for its screw holding strength, especially when subjected to the impacts of kids climbing/running/jumping on the stairs.
    – FreeMan
    May 5 at 15:36

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