Orla

From having done this in a house of the same vintage, two practical notes.

Do not connect the ground terminal to the neutral to make a tester show a ground. This is occasionally suggested and it is genuinely dangerous — it puts normal return current on the appliance case and makes an open neutral lethal. Any tester showing a proper ground where none exists is worse than one showing the truth.

A plug-in tester will report a fault on these outlets and that is expected. Those testers detect the missing ground and cannot detect a working interrupter without a ground. Use the test button on the device itself, monthly.

Also worth knowing that in some cases running a single ground conductor back to the panel for one circuit is permitted and is far less work than rewiring. Worth asking about for the circuits that feed your electronics.

On when to get an engineer, and the answer is more often than people like: now, in your case.

The signals that it is not a do-it-yourself decision:

• Holes or notches that look large relative to the joist depth, which yours do.
• Anything cut into the top or bottom edge.
• Multiple joists affected, which yours are.
• A long span, or a floor that already deflects or bounces.
• A bathroom, which means a wet room and possibly a heavy fixture.

A structural engineer's visit for a domestic floor is not an enormous expense and you get a specified repair rather than a guess. That specification is also what a building inspector will want, and what a future buyer's surveyor will want to see.

Worth adding: a joist that has been like this for decades without visible problems is not evidence it is adequate. It is evidence it has not yet been loaded enough.

The two non-electrical reasons matter as much and get less attention.

Tripping. A heater is a heavy hot object on the floor and the cord runs across a room. Pulling one over is a fire and a burn, and it is a far more likely event than an overloaded conductor.

Placement. The reason people reach for an extension cord is that they want the heater somewhere without an outlet — often exactly the places you should not put one. Near furnishings, in a corner, against a bed. The cord enables the bad position, and the bad position is the actual hazard.

That is why the advice is absolute rather than conditional. A conditional warning would be technically better and would be followed by people who already understand the conditions, which is not the population the label is written for.

Practical tip once you have identified the conductors: mark them permanently before you cut anything else.

A dot of paint, a piece of heatshrink, a label. The number of times I have carefully determined a polarity, put the job down, and come back the next day to two identical white wires is more than I would like to admit.

On "is it acceptable to leave it until someone can come" — with the breaker off, yes, that is exactly the right state to be in. With the breaker on, no, and I would not sleep in the house that way.

The repair itself is usually straightforward for an electrician: open the wall at that point, cut out the damaged section, and join it properly in an accessible junction box, or replace the run. It is a small job and a bad one to improvise, mostly because the joint has to remain accessible and correctly enclosed.

One useful thing you can do meanwhile: photograph the location and measure from two fixed points. Once the nail is out, finding the exact spot again in a plastered wall is annoying.

Things to avoid, since you asked:

• Do not pull hard. The glue is frequently stronger than the outer layer of skin, and forcing it takes skin with it. Patience genuinely is the technique here.
• Do not use a blade to cut between them. It is suggested and it is a good way to add a cut to a stuck finger.
• Do not use acetone if the skin is broken, and keep it off anything you care about — it damages many finishes, plastics and varnishes.
• Do not heat it. Cyanoacrylate reacts with moisture and gives off heat as it cures; adding more heat is unhelpful and can burn.

If it is on or near an eye, or an eyelid, or inside the mouth, stop and get medical attention rather than trying anything from this thread. Those cases are genuinely different and are handled routinely by professionals.

For the gap in your gym training, the specific things that transfer:

• Horizontal pulling endurance. Higher repetition rows and pull-downs, sets in the fifteen to twenty-five range, which is unusual for a strength programme but matches what paddling asks for.
• Anything for the back of the shoulder and the mid-back. These are the areas that limit paddling and the ones a general programme under-trains.
• Extension endurance — holding an arched position, which is exactly the surf posture.
• General aerobic work. Paddling is a cardiovascular effort as much as a muscular one, and this is usually the missing piece for people who only lift.

Add those and the first month of any paddling sport gets noticeably easier.