“Further Investigation Is Recommended”: What Each One Costs and Which You Actually Need

Somewhere in your survey, probably more than once, is a sentence that ends "…further investigation is recommended before exchange of contracts." It is the most common recommendation in UK residential surveying and it is also the one that causes the most panic, because it reads like the surveyor has found something too serious to describe.

It hasn't. It means the opposite of what most buyers assume. It means the surveyor could see a symptom and could not see the cause — usually because establishing the cause needs equipment they didn't bring, access they didn't have, or a qualification they don't hold. It is an instruction to go and find out, not a verdict.

The problem is that nobody tells you what finding out costs. Your surveyor won't, because pricing other people's work isn't their job. The specialist they've sent you to has an obvious interest in the answer being yes. So here is the whole list: the eight investigations that get recommended, what each one costs in 2026, what it actually settles, which are worth doing before you exchange, which you can decline, and who should be paying.

Why the phrase exists at all

A RICS surveyor inspecting a house is working under real constraints. They are there for somewhere between an hour and half a day. They cannot lift floorboards, take down ceilings, dig holes, move the seller's furniture, or open up anything that would need making good afterwards. They cannot go into a loft with no boarded access or a cellar with no light. And they are not qualified to certify a gas or electrical installation even if they can see it is old.

So when they see cracking that runs through the bricks rather than the mortar, they can tell you it is there, describe its width and direction, rate it, and say what it might indicate. What they cannot do is tell you whether the foundation is moving, because that needs monitoring over months or a trial pit, and neither of those is part of a survey.

"Further investigation is recommended" is what a careful professional writes at exactly that point. Read as an instruction it is useful. Read as a diagnosis it will cost you sleep and possibly a house you should have bought.

The eight investigations, priced

A structural engineer's report — £500 to £1,200

Triggered by: cracking the surveyor considers more than cosmetic, bulging or leaning walls, a sagging roofline, floors visibly out of level, a bay window pulling away, or any mention of the word movement.

What you get: a chartered structural engineer visits, inspects, and produces a written report saying whether the movement is historic and stable or live and progressing, what caused it, and what — if anything — needs doing. If they cannot tell on one visit, they will recommend crack monitoring, which means telltales fixed across the crack and read over six to twelve months at £400 to £900 for the programme.

What it settles: almost everything. Most cracking in British houses is thermal movement, historic settlement that stopped decades ago, or a lintel problem — none of which is subsidence and none of which is expensive. Actual subsidence is comparatively rare, and when it is confirmed, the range runs £5,000 to £45,000 depending on whether it needs underpinning or just a tree removed and a drain fixed.

Worth it? Yes, whenever movement is mentioned. It is the single highest-value report on this list, because the gap between the cheap answer and the expensive one is the widest. Our guide to what a structural engineer's report covers goes through what to expect, and cracks in walls explains what you are likely to be looking at.

A drain CCTV survey — £200 to £400

Triggered by: "drainage requires further investigation", which appears on a large share of surveys almost by default. Also mature trees near the run, historic settlement to paths or patios, or a manhole the surveyor couldn't lift.

What you get: a camera down the run, a recorded video, and a report identifying cracks, displaced joints, root ingress and partial collapses, with a severity grading.

What it settles: whether you are buying a working drain. A collapsed or root-blocked run costs £1,200 to £8,000 to put right, and it is one of the few defects that can also make a mess of your garden and your neighbour's.

Worth it? Yes, on almost any pre-war property, and particularly where there are trees. Pound for pound this is the best-value investigation on the list — a £300 check against an £8,000 exposure. It is also the one buyers skip most often, because drainage sounds boring and roofs sound urgent.

A damp and timber report — "free", and that is the problem

Triggered by: elevated moisture readings, staining at skirting level, a mention of rising damp, or visible rot to timber.

What you get: depends entirely who you call. A damp-proofing contractor will inspect for free and produce a report recommending a chemical damp-proof course, injection, replastering and a guarantee. An independent damp surveyor with no remedial arm will charge £300 to £600 and will frequently tell you the problem is a blocked air brick, a bridged damp-proof course or a leaking gutter.

What it settles: which of the four damps you actually have. In UK housing, condensation is by far the most common, penetrating damp second, plumbing leaks third, and true rising damp a distant fourth. The damp-proofing industry tends to work that list in reverse.

Worth it? Get the independent one. A free survey from a company that sells the remedy is a sales visit, and it is how a £600 drainage fix becomes a £6,000 injected damp-proof course. Before you book anyone, check the external ground level: it must sit at least 150mm below the damp-proof course, and raised paths, decking and flower beds bridging it are the most common cause of what gets diagnosed as rising damp. Rising damp versus penetrating damp covers how to tell them apart, and wet rot versus dry rot covers the timber side, where the difference between the two findings is the difference between £700 and £20,000.

An Electrical Installation Condition Report — £180 to £350

Triggered by: "the electrical installation appears dated", a plastic consumer unit with rewireable fuses, no RCD protection, or any sight of rubber or lead-sheathed cable.

What you get: a qualified electrician tests the installation and issues a report coded C1 (danger present), C2 (potentially dangerous), C3 (improvement recommended) or FI (further investigation, again).

What it settles: whether "dated" means a £700 consumer unit swap or a £6,000 to £12,000 full rewire. Those are wildly different numbers and the survey will not distinguish between them.

Worth it? Yes, if there is any sign of pre-1970s wiring. An old-looking installation is very often perfectly serviceable — a house can have a 1980s rewire behind a horrible fusebox. Old wiring types covers what actually needs replacing, and what an EICR means for your purchase covers the report itself.

A gas and boiler safety check — £120 to £900

Triggered by: an old boiler, no service record, or a flue the surveyor could not trace.

What you get: a Gas Safe registered engineer checks the appliance, the flue and the installation. At the cheap end that is a safety check on a working boiler. At the top end it includes a power flush or remedial pipework.

What it settles: whether the heating works and whether it is safe. It will not tell you the boiler has ten good years left, because nobody can.

Worth it? Usually skip the pre-purchase version and budget instead. A boiler with no service history is a £2,400 to £4,200 replacement at some point regardless of what a check says today, and a tired system with old radiators and pipework runs £5,500 to £12,000. Price that into your offer rather than paying to be told the boiler is old, which you already know. The exception is any hint of a flue problem or a gas smell, which needs answering immediately and is not a negotiating matter. Boiler and gas safety findings has more.

An asbestos survey — £200 to £600, or £50 to £100 a sample

Triggered by: "possible asbestos-containing materials", which appears on a large proportion of surveys for anything built or altered before 2000. Artex and textured coatings, garage and outbuilding roofs, soffits, boiler flues, old floor tiles, insulation board around meters.

What you get: either a single sample tested at a UKAS laboratory for £50 to £100, or a management survey of the whole property for £200 to £600.

What it settles: whether the material contains asbestos and, more usefully, what type. This matters more than the yes or no. The overwhelming majority of what turns up in houses is low-risk bonded material — cement roof sheets, textured coatings, floor tiles — which is safe left undisturbed and is legal to leave in place. Removal costs range from £400 for a small area to £6,000 for licensed work on insulation board.

Worth it? Test if you are planning work that would disturb it, or if the material is already damaged. If it is a sound Artex ceiling you have no plans to touch, the honest answer is that testing tells you something you will then do nothing about. Never sand, drill or scrape suspect material to find out.

An arboricultural report — £300 to £800

Triggered by: mature trees close to the building, particularly on clay soil, and doubly so if the survey has also mentioned cracking.

What you get: an arboriculturist identifies the species, assesses the root spread against the foundation depth and soil type, and advises whether the tree is implicated in any movement — and, importantly, whether removing it would make things worse.

What it settles: the tree question, which is genuinely counterintuitive. On shrinkable clay, removing a large mature tree can cause heave as the ground rehydrates and swells, which does more damage than the tree was doing. A tree with a preservation order or in a conservation area cannot be removed anyway without consent.

Worth it? Only where trees and movement appear together. A tree near a house is not a defect on its own. Tree-related work runs £500 to £4,000.

A roof inspection — £150 to £400

Triggered by: "the roof covering is nearing the end of its serviceable life", a phrase that appears on almost every survey of a house over eighty years old.

What you get: a roofer or a drone survey gets close enough to see what the surveyor could only see from the ground with binoculars — nail sickness, perished underfelt, cracked verges, failed flashings.

What it settles: whether you are looking at £250 to £900 of slipped tiles or £8,000 to £18,000 of full strip and re-cover. That is the widest cost gap in the whole report, sitting behind a phrase that gives you no clue which end you are at.

Worth it? Yes, but get it from a roofer who is quoting for the work rather than paying for an independent inspection — quotes are free, and two or three of them will bracket the number well enough. Watch for the roofer who inspects and immediately recommends the most expensive option. 'Roof covering is aged' covers how to read the phrase, and chimney stack and flashing issues covers what usually goes with it.

What all this comes to

If a survey recommended every investigation on this list you would be looking at roughly £1,700 to £3,700 before you have bought anything, on top of the survey fee. Almost no survey recommends all eight.

A realistic pre-war terrace or semi generates two or three: usually drainage, something structural, and something damp-related. That is £900 to £2,200, against defects that between them can run to five figures. Framed against the purchase price it is rounding error, and framed against the negotiation it frequently pays for itself several times over.

Do them before exchange, or after?

In England and Wales you can walk away at no cost right up to exchange of contracts, and you can renegotiate right up to it too. So anything that could change your offer or your decision belongs before exchange. That means:

• Before exchange, always: structural, drainage, and anything the surveyor rated Condition 3
• Before exchange if you are stretched: electrical, damp
• After completion is fine: gas and boiler, roof detail, asbestos you are not going to disturb

In Scotland the sequencing is different because the Home Report comes before the offer and a concluded missive is binding, so investigations that would change your number have to happen earlier, before you offer.

Who should pay

You will pay, usually, and that is normal. But three situations are worth pushing back on.

Where the finding is serious and the seller will face the same question from the next buyer, ask them to fund it or split it. They frequently will, because they get the answer too and because the alternative is starting again with a buyer who will raise the identical point.

Where a specialist has already been out for the seller and produced a report, ask for a copy before you commission your own. There is often one sitting in a drawer.

Where the investigation confirms work is needed, the cost of the investigation itself goes into the schedule you take back to the agent. It is a cost you incurred because of a defect in their property.

What to do with the answers

An investigation that comes back clear is worth the money and needs nothing further — write it off and move on with more confidence than you had.

An investigation that confirms a problem gives you a costed, evidenced finding, which is much stronger material than the survey it came from. A structural engineer's report saying the movement is live is not a worry, it is a document. Put it and its cost into a schedule of the Rating 3 items, total it, and take that to the agent. Buyers who present a costed schedule typically recover somewhere between half and all of the urgent repair costs; buyers who forward the survey with a note saying they are concerned usually recover nothing.

There is more on the wording and timing in how much you can negotiate off a house price after a survey, and if you want to build the schedule yourself, the survey repair cost calculator prices the 57 findings that come up most often and sorts them by urgency.

When it really is a warning

Occasionally the phrase is doing more work than usual. Treat these as serious until proven otherwise:

• Further investigation of structural movement combined with a recent crack, especially one wider at the top than the bottom, or one that has been filled and reopened
• Dry rot suspected — the only timber defect that spreads through masonry and the only one where the range reaches £20,000
• Japanese knotweed on or near the property — a mortgage problem as much as a garden one, and £3,000 to £12,000 to treat
• Alterations with no building regulations sign-off, particularly a loft conversion or a removed load-bearing wall, where the cost of regularising runs £800 to £6,000 and the cost of getting it wrong is structural

Those four are the ones where "further investigation" is genuinely a flag rather than a formality. Everything else on this list is far more likely to end in relief than in a bill.

If you want somebody to read the whole thing

Working out which investigations matter, which are boilerplate and what the answers are likely to cost is the bulk of what we do. Send us the report and a builder goes through every finding, tells you which of the recommendations are worth acting on before exchange, and puts a realistic figure against each item — £59, back within 24 hours.

If it is one question rather than a whole report — is this crack a problem, does this quote look sensible — ask it free. No card, no obligation.