Advice: which clamp to buy to fix warped door?

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I need to buy a clamp to fix a warped front door, same as shown here:



He shows the clamp briefly here:


Is that a normal F-clamp? The thing is the two ends of the clamp must be able to swivel so I can get them in opposite positions to one another. I'm not sure F-clamps can do that?

My door is warped in the center, not at the top as in the above video, so I'm planning to use two blocks of wood (one at the bottom and one at the top) and the clamp in the middle, so that one end grabs the door and the other end (swivelled by 180 degs, to form an S shape) can grab the door frame on the other side.

Thanks in advance for any help.
 
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Berk. Says it all, really - he's a lawyer... not a joiner. And that is a thinnish glazed door, not a slab door or a frame and panel door

For every successful door straightened this way I bet there will be 30 or 40 which won't straighten fully, especially if dealing with 50mm thick frame and panel hardwood front doors. This is because the timber has stresses in it which occurred as the tree was growing (and may explain why joiners prefer straight grained wood) and are often resistant to being removed by clamping.

If your door has only a slight amount of warp (up to about 10mm) it may be a lot easier to simply undo the door frame screws on the lock side (middle an upper or middle and lower only), pull the frame over and refix then reseal it. Similarly, you can get a further 5mm or so of movement by reseating the hinges.

As to the type of clamp, a traditional F- or G-clamp has a ball-jointed foot that can adapt to out of parallel surfaces - just make sure that you put a plywood or timber pad beneath both jaws to protect your door and frame surfaces). These modern clamps with two flat faces are designed for bench glue-ups and aren't always the best clamps for site work

Is clamping a door for a few minutes supposed to straighten it?
No. You need to clamp it potentially for days, at least in dry weather. But what it can do is break the glue bonds in the joints, especially if they are a relatively inelastic glue such as UF glue. With flush doors (i.e. chipboard or laminboard core) flattening for a couple of weeks under a lot of weight can work (we stack flush doors flat on site to keep them flat), but even that isn't a sure bet.
 
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Thanks so much for your replies so far. To add a little context my front door warped inwards during the recent heatwave and can no longer be locked. At the top and bottom it's flush with the frame, but it gradually sticks out of just about 2-3mm towards the center part. It's a frame and panel front door. It happened already once a few years ago, but it sorted itself out after a few days, but this time it's been a few weeks already and it still cannot be locked. I just googled how to fix a warped door and thought I could give this a go.

If your door has only a slight amount of warp (up to about 10mm) it may be a lot easier to simply undo the door frame screws on the lock side (middle an upper or middle and lower only), pull the frame over and refix then reseal it. Similarly you can get a further 5mm or so of movement by reseating the hinges.

So do you reckon I should I avoid trying altogether the clamp thing altogether? Of course I don't want to damage the door. I'm not sure what you mean by pulling the frame over?
 
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It happened already once a few years ago, but it sorted itself out after a few days, but this time it's been a few weeks already and it still cannot be locked. I just googled how to fix a warped door and thought I could give this a go.
If that worked consistently as an approach then no joinery firm would ever bother making sure that the stiles of a frame and panel door were made from straight grained timber, because you could always just pull it into shape with a clamp. Instead they do go to the trouble of choosing relatively straight-grained wood. The fact that it went back into position on it's own in the past says to me that the timber has some internal stresses and that the current hot, dry weather has dried it out sufficiently to cause this. Perhaps it wasn't sufficiently well kilned in the first place (i.e. it was slightly damp when the door was manufactured). It is quite possible that when the weather changes it will take on some moisture and return to it's previous shape. Wood isn't steel, it doesn't just bend, it is more like an elastic plastic with a degree of memory

Could you tell me what species it is and what the door finish is? Also have the top and bottom edges of the door been sealed/finished and does the door fit the frame side to side, or has there been any "planing-in" done to get it to fit the frame? Just trying to figure out if there is another approach which can be taken

So do you reckon I should I avoid trying altogether the clamp thing altogether? Of course I don't want to damage the door.
I'm a little wary of doing this, more because experience tells me that weighting a door down doesn't always work and that if you put too much stress into a dowelled joint or a mortise and tenon joint (the two main types of joint used on exterior frame and panel doors) you can crack the joints. With doors which have been stored leaning up against a wall (and taken on a bend) the only approach is to store it in the same way, but reversed to reverse the bend. Depending on how bad the bend is this might take a week or two in normal weather

I'm not sure what you mean by pulling the frame over?
It's more for internal doors on thinner casings or linings, but if the top or bottom corner of a door stick out from the door frame it is possible to unscrew the door frame from the wall and then twist the leg of the frame to match the twist in the door, repack and refix the leg(there are packers behind the screws) and seal it. In other words, instead of trying to bend a fairly substantial door you bend a much less substantial frame leg, which is a lot easier. You can also deal with a sticking-out door (on the lock side) by toeing-out the diagonally opposite corner on the hinge side (so a door sticking out at the top lock side corner can be pushed back in by adjusting the bottom hinge outwards - if the door has 3 hinges the middle hinge will need to be moved as well). You literally undo the hinge, pull the door out a few millimeters on the hinge side (I use a small cat's paw bar into the rebate) then refix it. This causes the diagonally opposite corner of the door to go in. Minor discrepancies on the hinge side of a door opening are generally much less noticeable. A combination of the two techniques can be useful to disguise the adjustments

The same sort of approach works on casings/linings of interior doors, although the architraves obviously do need to be removed first
 
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If that worked consistently as an approach then no joinery firm would ever bother making sure that the stiles of a frame and panel door were made from straight grained timber, because you could always just pull it into shape with a clamp. Instead they do go to the trouble of choosing relatively straight-grained wood. The fact that it went back into position on it's own in the past says to me that the timber has some internal stresses and that the current hot, dry weather has dried it out sufficiently to cause this. Perhaps it wasn't sufficiently well kilned in the first place (i.e. it was slightly damp when the door was manufactured). It is quite possible that when the weather changes it will take on some moisture and return to it's previous shape. Wood isn't steel, it doesn't just bend, it is more like an elastic plastic with a degree of memory
Thanks so much for your valuable input and explanations. It sounds like it may be sensible to just wait and see it if does go back to normal after the hot weather stops.

Could you tell me what species it is and what the door finish is? Also have the top and bottom edges of the door been sealed/finished and does the door fit the frame side to side, or has there been any "planing-in" done to get it to fit the frame? Just trying to figure out if there is another approach which can be taken

I am not sure what species the timber may be but I am attaching a couple of photos should they be of any help identify it. The door has been painted white and the top and bottom have been left bare. I am unable to tell for sure if it did fit the frame or has been planed - the impression I have is that it has not been, as it's very flat on the sides, but that's just a guess and I may be wrong, as I'm clearly not an expert. It was more than likely installed when they built the house back in the 80's, it was already here when we moved in 15 years ago. It may be worth mentioning that even if it is technically the front door, a small porch has been built at the front of the property a very long time ago, so it's no longer exposed to the elements as there is another front door to the porch now.

I'm a little wary of doing this, more because experience tells me that weighting a door down doesn't always work and that if you put too much stress into a dowelled joint or a mortise and tenon joint (the two main types of joint used on exterior frame and panel doors) you can crack the joints. With doors which have been stored leaning up against a wall (and taken on a bend) the only approach is to store it in the same way, but reversed to reverse the bend. Depending on how bad the bend is this might take a week or two in normal weather

I understand, and take your comment onboard. I will not go ahead with that
 

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Last year I had to deal with a 100 year front door that had warped a lot (in more than one dimension). The customer didn't care too much about the cost but wanted to keep the original door.

I adjusted the hinges to find a "happy" medium and then spent hours chiselling away parts of the exterior door stops and back filled the other parts with two pack filler. At the top of the door, I had to back fill by up to 6mm down to 2mm.

The easiest way is to run yellow Frog tape along the door edges, apply the filler to the door stops and then close the door and wait for the 2 pack filler to set. Took about 14 hours in total though (excluding painting).
 
OP, I'd recommend that if (when?) it goes back to shape that you prime and paint the exposed top surface with an oil-based gloss paint to thoroughly seal it. I suspect that the exposed wood at the top of the door isn't helping the situation
 
OP, I'd recommend that if (when?) it goes back to shape that you prime and paint the exposed top surface with an oil-based gloss paint to thoroughly seal it. I suspect that the exposed wood at the top of the door isn't helping the situation

And the underside.

Although not the cased here, decorators often paint the top, but cannot get to the underside whilst the door is hanging.
 
Agreed. It's a common cause of failure on fire doors - the bottoms rot out because they are at ground level, quite often above a threshold or seal and often unprotected unless the joiner paints them before installation. In this case I was particularly concerned by this warping, at the top of the door, potentially being caused by the timber drying out excessively - unusual, but seems to be the case
 
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Thanks everyone. I'll sit tight and wait for the wet weather to come back with my fingers crossed. And if it ever gets back to its normal shape I'll paint top and bottom.
 
Very interested in hearing whether this clamp method works or not, as we are facing the same problem and watched the same youtube video... though ours are some second-hand internal doors we found for free, but after the carpenter hung them the top corner has a gap....
 

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