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I'm replacing some old deck boards. It was impossible to unscrew these old boards so I pried them up. Now I have many rusted and bent screws sticking up from the joists. Not sure how I can unscrew these. Can I just cut them off with a grinder? If so, how do I avoid hitting the old screw bodies when screwing in the new boards? Is it a good idea to sister some 2x4s to the existing joists and screw the new boards into these? The existing joists are in good shape.

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  • First try unscrewing with a pair of ViceGrips pliers.
    – Hot Licks
    Commented Aug 2, 2022 at 2:54

4 Answers 4

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I had replaced my deck boards many years ago and broke the screws off with a pair of vice grips by bending them back and forth until they broke off, but they were very badly rusted. I had tried a prybar, but they snapped too high. If yours are not super rusty, locking pliers rotated counter clockwise will remove them. Don't worry if they are a bit proud of the joist (1/16"); they will bury themselves into the new wood. You almost certainly won't hit and be stopped by an old screw. the new screw will hit off center and grab adjacent wood.

I also cannot recommend Torx head deck screws enough; if you need to back them out in 10 years, you'll be able to.

FYI, this is the perfect time to apply a new solid stain/wood sealant on the joists and supporting members, even if they are in good shape.

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  • Good point about new protection for the joists. That is usually where rot starts.
    – crip659
    Commented Aug 2, 2022 at 0:26
  • Yes, great point about the sealant. I will do that. I was concerned about hitting old broken off screws as it happened to me not long ago when working on the front porch. Hopefully my one-in-a-million bad luck has thus run out. And yes,I have a Torx screws, they are excellent going in and out.
    – user387226
    Commented Aug 2, 2022 at 1:25
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Use a nail puller/pry bar to remove them. Same as what to do with nails.

Hammer them in.

Screws are usually small enough, that hitting them dead on takes quite a bit of luck.

Grinding produces sparks so extra care must be maintain. Usually also slowest way.

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  • thanks for the reply. For the screws that I hammer in or cut off, how do I avoid hitting them with the new screws? Do you think the sistered 2x4 idea will work or is it more pain than it's worth?
    – user387226
    Commented Aug 1, 2022 at 23:33
  • @user387226 You have 5 or 6 inch wide boards, you really think you can hit something about 1/8 inch diameter blind.
    – crip659
    Commented Aug 2, 2022 at 0:09
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If the existing joists are sound, there is no need to sister additional joists. Think about what forces the fasteners holding the deck boards to the joists are asked to handle: not much. The screws are there to hold the deck boards in place on top of the joists; maybe resist lifting up in a stiff wind.

A strong pair of wire cutters or a grinder would cut them. I have had some success removing screws with damaged or missing heads by chucking them up tightly in my cordless drill and going slowly backwards. A tedious job for a whole deck.

As the other answer states, hitting an old screw which has been cut off with a new screw takes some luck.

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Locate and avoid them with a sensitive stud finder. If they are ferromagnetic, hanging a neodymium magnet pendulum may enable you to locate them as it tends to line up.

Alternatively, develop a system of marking the support beam to indicate how far from an edge they are in each case. And/or vary their positions, alternating left and right of center. They can be just as effective in these locations

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