Knowing when to stop and how to get a quote you can trust

Four things in a house will hurt you or bankrupt you if you get them wrong: gas, mains electricity, structure, and water you can't see. Everything else is negotiable. Start there and most of the "should I do this myself" agonising disappears.

Gas is the clearest line of all. In most places the law requires a registered, licensed engineer for anything touching a gas supply, appliance or flue. Not because the fittings are difficult. Because a slow leak or a blocked flue kills people in their sleep, and there's no intermediate failure mode that warns you first. You don't get a second attempt at carbon monoxide.

Mains electrical work sits just behind it. Swapping a like-for-like light fitting or a socket faceplate is within reach of a careful adult who knows how to isolate a circuit and test that it's dead. New circuits, consumer unit work, anything in a bathroom or outdoors, anything that needs certifying and signing off — that's a qualified electrician, and in a lot of jurisdictions it's a legal requirement, not a preference. Ask your local building control what's notifiable where you live before you start, not after.

The structural test is simpler than people think

If removing it changes how load travels to the ground, you need somebody with letters after their name. That includes chimney breasts, internal walls you are "pretty sure" aren't load-bearing, and widening any opening. A structural engineer's calculation costs a fraction of underpinning a sagging floor, and your insurer will ask for it if anything ever moves.

Roofs deserve their own rule. It isn't the roof, it's the ladder. Most serious DIY injuries at home come off ladders and stepladders, and they don't happen at thirty feet. They happen at eight, doing something quick, with the ladder at a bad angle on a soft lawn. If the job needs both hands and a lean, get someone with a tower or a harness.

Then there's the invisible water. A dripping tap is a washer. A damp patch on a ceiling below a bathroom is an investigation, and investigations mean opening things up. If you can't trace it in twenty minutes with a torch, you're paying someone either way. Better to pay them before the plasterboard is wet through.

What you can genuinely take on

Plenty. Filling and painting. Silicone replacement around baths and sinks, which is a genuinely high-value hour of work and stops most bathroom rot. Clearing gutters, from a stable platform. Bleeding radiators. Replacing a toilet fill valve or a tap washer. Easing and adjusting doors. Draught-proofing. Fitting shelves, curtain poles, blinds. Changing door locks. Servicing a lawnmower.

The common thread: these all fail politely. A bad paint job looks bad. A bad silicone bead peels off and you do it again. Nobody gets hurt and nothing hidden gets worse. That's the real test for DIY, not difficulty.

The other honest reason to call someone is time. A good tradesman does in a day what will take you three weekends and two trips to the merchant, and does it better. If you earn money at weekends, or you have small children and the weekends are the only time you see them, the maths often favours paying.

Getting a price that means something

Know the difference between an estimate and a quote. An estimate is a best guess and can move. A quote is an offer to do defined work for a defined figure, and once you accept it, it's a contract. Ask which one you're being given. If someone won't say, you've learned something.

Get three. Two isn't enough to spot an outlier and four wastes everyone's time. Brief all three identically, ideally in writing, so you're comparing the same job. The single biggest cause of wildly different prices isn't greed, it's three tradesmen quoting three different jobs because the customer described it three different ways.

Write your brief before the first visit. Say what you want done, what standard you expect, who's supplying materials, and what your deadline is. Include photos. Say what you're not asking for, too — that stops a quote quietly ballooning to include making good work you were happy to do yourself.

The eight questions

Ask these on the visit, and ask all of them every time.

• Is this a fixed price or a day rate? Day rates suit unknowns like chasing a leak. Fixed prices suit defined work. Mixing them is where arguments start.
• What's included in materials, and who's buying them? Get the allowance in writing. "Tiles up to a certain value per square metre, customer to choose" is a real line. "Materials extra" isn't.
• Is tax included? In the UK, ask whether the figure includes VAT. Two quotes can look thousands apart and be identical.
• What's the payment schedule? Staged payments against milestones are normal. A large deposit before anyone has bought anything or turned up isn't.
• What happens if you find something behind the wall? The answer you want is a phone call and a written variation before extra work starts. Agree that now.
• Who's actually doing the work? The person quoting isn't always the person turning up. Fine, but you should know.
• What guarantee comes with it, and does it come on paper? Ask about their liability insurance too.
• Can I see two jobs like this you finished in the last year? Photos are fine. A phone number for the customer is better.

The signals worth walking away from

Pressure to decide today. A discount that only exists if you sign now. Cash-only with no paperwork and no guarantee, which leaves you with no recourse and possibly no insurance cover if it goes wrong. Reluctance to put anything in writing. A quote so far below the other two that something has been left out — find out what before you get excited.

And the quiet one: somebody who doesn't ask you questions. A good tradesman interrogates the job. They look under the sink, into the loft, at the fusebox. If someone quotes from the doorway in ninety seconds, they're either extraordinary or they're planning to renegotiate later.

When the price moves

It sometimes will, honestly. Old houses hide things. What separates a fair variation from a squeeze is the process: stop, explain, price it, get your agreement, then continue. If you're presented with extra costs only at the end, that's a failure of process even if the work was genuinely necessary.

Keep a contingency of around ten percent on small jobs and more on anything involving old plumbing, old wiring or old plaster. Not because you expect to spend it. Because having it means you can make good decisions mid-job instead of panicked ones.

Hold back a final payment until you've walked the job with the tradesman and listed anything outstanding. Do that walk in daylight. Bring a torch anyway.

The tradesman you want isn't the cheapest and usually isn't the one who can start tomorrow. He's the one who's booked six weeks out, answers his phone, and tells you plainly that half of what you asked for isn't worth doing. Wait for him.