Help with removing rusted screws

ThisIsWeird

Realistically, I can't see any way to drill down inside the shaft of a screw, rusted or not. If anyone here can manage this, then uberkudos.
The only any I can think of to actually 'remove' a rusted, headless screw by unscrewing it, would be to dig into the board far enough to catch the top of the remaining screw in the jaws of a drill, and slowly reverse. This would obviously leave a cone-shaped hole that would need filling. If attempting this, I like John's idea of giving the screw a good hard tap first to try and break the bond.
An alternative should work, tho', be easier, and leave less damage, quite likely coverable by the replacement screw head.
You'll need to find a short piece of metal tubing, ID to match the screw's OD, and a thinnish wall thickness - so likely 4mm ID, 5-6 OD. Many DIYers will be able to place their hands on such a thing, and some may even have a lathe to knock one up. Roughen/notch/serrate the end of the tube. Remove the head of the screw if still there by drilling it off. Then drill the tube down over the screw until you contact the joist. The resulting hole should be coverable by the replacement screw's head, going up a size if needed. Add lots of rot preserver, perhaps even fill the hole first and redrill for the new screws. This should be both easy and successful.
(Or, prise the boards up, hoping for the best. Or multi-tool by inserting the blade betwixt joist and board, but both these solutions require a neighbouring board to be liftable first.)
Something like this should do. The top flange will need breaking or grinding off, and the resulting end made into a cutting edge by, say, tackling it with a hacksaw to give it 'teeth'. Put threaded bottom end in t'drill, and drill away gently. 

https://www.screwfix.com/p/rawlplug-hollow-wall-anchors-m4-x-38mm-20-pack/54782

the_lunatic_is_in_my_head

Icecream_Gladiator said:

What sort of drill bit would you recommend to drill out the screw?

https://www.ebay.co.uk/itm/273678648316?var=573196923813

Drilled out the screws on our UPVC door handle no problem. 

Bookworm105

JohnB47 said:

I know you're talking about screws but when I want to get rusted nails out I always give them a sharp tap (or three) with a hammer, to actually push them a bit into the wood first. This breaks the grip that rust creates.

I would suggest trying placing a suitably shaped piece of metal on the screw head (a big nail or old drill bit) and hit that firmly a few times with a hammer to hopefully break the rust grip. It might work and costs nothing to try.

Good luck drilling out a screw! I'll be impressed if you can do it.

I would like to see you succeed with prising a full thread screw without causing significant damage to the wood unless the screw is either too short (so barely penetrates the "joist") or the "joist" is soft/rotten and so the screw is barely gripping.

ThisIsWeird

Icecream_Gladiator said:

What sort of drill bit would you recommend to drill out the screw?

I only have a 10v cordless drill, would that be enough power?

Hi Icecream.

You will not succeed in 'drilling out' the screw. Whatever drill you use, you will not be able to keep it central in a solid screw shank which is likely to be only around 3mm diameter, and made from hardened steel. The drill will keep slipping sideways, and you'll butcher the surrounding timber.

If, for any other option, you need to remove the screw's head, then that can be done fairly easily by drilling down in the middle of the head using a drill bit that's larger than the shank of the screw, so a 5mm upwards drill should do, tho' 6+mm is better.

If you look at a screw sideways, you should see that, once the drill goes through the head and reaches the shank, the head will just fall off.

You'd want to remove the head if you were planning to try and prise off the boards, and this might well work ok if the screw threads are also rusty and weak, or the timber surrounding the screw slightly soft, which is very often the case; that's where rots usually begins as water gets down around the screw thread.

So, prising the boards up from the joists could well work. There's also a reasonable chance the screws will just snap where they enter the joists as that's where most of the force will land.

Of course, to be able to 'prise', you need to be able to access the board/joist join first, so that will require one other board to be removable first. Or, can you get to one end of a board and prise it up there? If so, lift the board and slide in something to hold the board up. Slip in a longer pry-bar and keep easing the board upwards bit by bit, pushing the spacer in further as you go. Listen out for the board creaking, tho'...

Seriously consider my earlier idea, tho'. What tools do you have available to you? You should be able to remove the flange from the wall anchor by bending it repeatedly with pliers, and expose what will be a reasonable core-drill. If it works, you will be giggling instead of cursing. 'Core' slowly.

Mistral001

If you can get one or two boards up by drilling 6 or 7 holes with a small drill bit around each hole and then using a one-handed hacksaw to cut the screws off from below the rest of the boards.  Then turn the boards over and  use a punch and  a hammer to make the screw heads protrude enough to get a claw hammer under them to remove the screws.  You will badly damage the one or two boards where you had to drill out the screws, but at least the other boards should be salvageable

See below for the hacksaw: 

https://www.screwfix.com/p/irwin-24tpi-metal-plastic-mini-hacksaw-10-250mm-/99650.

twopenny

Soak with a water repellant Wd whatever

Then use a piece wide rubber band  the Post Office use and place on the screw with the drill bit on top.

It takes a couple of goes but works a treat in removing screws where the head has been - screwed

Thanks YouTube

https://www.youtube.com/watch?v=819nd6fPXqk

outtatune

If you do decide to drill any part of the screw, make sure you wear eye protection (regular glasses aren't enough). 

JohnB47

Bookworm105 said:

JohnB47 said:

I know you're talking about screws but when I want to get rusted nails out I always give them a sharp tap (or three) with a hammer, to actually push them a bit into the wood first. This breaks the grip that rust creates.

I would suggest trying placing a suitably shaped piece of metal on the screw head (a big nail or old drill bit) and hit that firmly a few times with a hammer to hopefully break the rust grip. It might work and costs nothing to try.

Good luck drilling out a screw! I'll be impressed if you can do it.

I would like to see you succeed with prising a full thread screw without causing significant damage to the wood unless the screw is either too short (so barely penetrates the "joist") or the "joist" is soft/rotten and so the screw is barely gripping.

Where did I suggest 'prising a full head screw'? Most intelligent people will have read my post as suggesting an action that would break the hold of rust before unscrewing the screw.

knightstyle

This would loosen the screws. https://www.ebay.co.uk/itm/235243139279?itmmeta=01HZQ4DK2QTBMQA6XNJ737EJRV&hash=item36c59570cf:g:JGoAAOSwRcJlH2t-&itmprp=enc:AQAJAAAAwBTf9OMwesrA2ka2UtFuhVIzljX5lX404DVJDL5OlSwIZjPji/NVXDkH2I9JZ5W0WfGmGYVhQxqGMO6pEhn/g5jSQVTpcnrSMaugiMZePokGpG/aQ/85L46Us+CQnUttw9FMmucHomz8KMQrC00twHAY7ll4wUIRYCdBayu9I2hdIYJOcw9EBYyNAwMVpL6Op21wKsGbXd7AvOSCorZGhC04buITZChyLN0ogTlOCOzPaMaz+9WCgk8/g1fjy++dRg==|tkp:BlBMUMKxtuT9Yw

Icecream_Gladiator

Thank you for all your comments. I was able to remove all the screws without damaging the decking boards too much.

I have another question, though. The decking sits on a concrete slab, probably 20cm thick, not sure how much exactly.

I am having a soil pipe replaced, which is buried underneath the slab. It's cracked and overgrown with roots.

Presumably the workmen will have to break up the concrete in order to get to the pipe.

How soon after they finish the job and pour in new concrete can I replace the decking? A few days, a week, longer than that?

The decking joists are fixed to the slab with concrete screws.