Keeping water out: roof, gutters, ground and walls

A damp patch on a bedroom wall makes most people look at the bedroom. Often the water came from outside: a gutter spilling over, a downpipe leaking against the brick, soil or a patio built up against the wall. The sources this lesson read put those causes first because they're cheap to check: the University of Minnesota Extension's rule is to "first do the things that are easy and low-cost".² This lesson teaches the checks that find them, in a British house and an American one, and where a householder's part in the job stops: at the top of a ladder you should not have climbed, on a roof, and at a gutter that might be asbestos cement or sit under an asbestos cement roof.

Nothing in this lesson has you climb anything. The checks are done from the ground, from a window and inside the house, and the one job that needs a ladder, clearing a gutter, goes by lesson 15, "Ladders and working at height", and lesson 16, "Stepladders, and what the ladder injury figures count".

Four kinds of damp, and the one that comes from outside

The official guidance on damp this course uses most is English government guidance written for landlords, "Understanding and addressing the health risks of damp and mould in the home". It names four kinds. Condensation damp is moisture from inside the home settling on cold surfaces, and the guidance calls it "the most common form of damp". Rising damp is moisture from the ground. Traumatic damp is a leak from pipes, baths or tanks, or water from outside such as flooding. And: "Penetrating damp is water that gets into the building from outside due to defects in the walls, roofs, windows or floors."¹

This lesson is about the fourth. Condensation and rising damp are lesson 18's, "Damp inside: condensation, mould, ventilation and rising damp", and leaking pipes were lesson 2's. But the kinds are not sealed off from each other. The guidance says "traumatic or penetrating dampness may exacerbate condensation dampness", so a wall wetted from outside can make the room's own moisture worse.¹

Two more things from the same guidance belong at the start. It speaks directly to blame: "We are absolutely clear that it is totally unreasonable to blame damp and mould in the home on ‘lifestyle choices’", and it puts the fundamental cause in "building deficiencies, inadequate ventilation, inadequate heating and/or poor energy efficiency, not tenants’ normal domestic activities".¹ Penetrating damp is a building defect by definition. And it tells landlords, who own the building, that they "should not assume they will be able to diagnose the problem themselves in all instances".¹ This lesson teaches the checks that are cheap and safe to make. It does not make you a surveyor.

If you rent, the looking in this lesson is still yours. Whether a repair is yours or your landlord's is tenancy law, which this course does not teach. The US Environmental Protection Agency (EPA) tells renters to "Report all plumbing leaks and moisture problems immediately to your building owner, manager, or superintendent."¹³ That's US advice. The English guidance above, written for landlords, says "tenants are expected to report damp and mould in their homes".¹

The guidance lists the outside checks, in its words: "damaged or blocked pipes, gutters or downpipes"; "broken seals around windows or ill-fitting windows that do not close fully"; "visible structural or facade defects, such as cracks in render or the foundation, missing or broken roof finishes"; and a "bridged (compromised) damp proof course".¹ The rest of this lesson takes those in the order water meets them: the roof, the gutter, the downpipe, the ground, the wall.

How much water a roof sheds

The arithmetic is simple enough to do for any roof, and this course's rule for it is in metric: each millimetre of rain on each square metre of roof is one litre of water. A square metre covered 1 mm deep holds a thousandth of a cubic metre, which is a litre. Use the area the roof covers, roughly the house's footprint. (The rule and the footprint are this course's arithmetic, not the source's.) In feet and gallons, the extension service's figure scales: 1,250 gallons on 2,000 square feet is 0.625 gallons per square foot per inch of rain.

Here's why the number matters. All that water leaves the roof at a handful of points. The extension service: "Without proper grading, gutters and downspouts, some of this water flows into the basement."² And of a downpipe (a downspout, in American English) that simply stops at the foot of the wall: "A downspout without an extender or splash block is worse than no downspout at all. It is depositing the huge volume of rainwater from the roof in a single concentrated location near the basement."² An extender is a length of pipe, and a splash block a shaped block on the ground, that carries the water away from the wall.

A roof worked through, with a gap for you

A detached house in Aberdeenshire covers about 9 m by 8 m, so 72 m². A wet autumn day brings 25 mm of rain. By the rule, 72 × 25 = 1,800 litres come off the roof. Half the roof slopes to the front, into a gutter with a downpipe at each end, so about 900 litres come off that half and about 450 go down each front pipe (the back half has its own). Split your own roof the same way: by the part of the roof each gutter serves. If the back of one pipe has split, that is the water that runs down the wall behind it.

Gutters and downpipes

Here the countries' sources differ in what they cover, so they are set out side by side.

In Britain

Historic England, the public body for England's historic environment, publishes a maintenance checklist for older homes (this course read the live page on 26 September 2026). It's written for older homes in England. This course read no equivalent for Scotland, Wales or Northern Ireland, and on this course's reading its gutter and pipe checks suit any house. Its reason is damp: "Damp is a major cause of deterioration." And it asks owners to notice "design features or details that make your home more vulnerable to decay (for example concealed gutters or internal rainwater pipes)".⁴

It takes gutters and downpipes, which it calls rainwater pipes, in one list: "Inspect and clear any debris or blockages after heavy leaf fall, at least every autumn and preferably more often". Then it asks four questions: "Are there any leaking joints?"; "Does rainwater cascade over the gutter from the roof?"; "Does the water pool in any one area?"; and "Do the gutters slope correctly towards outlets?"⁴

Under the cascade question sits the most useful single instruction in this lesson: "Inspect while it is raining and note any leakages". For the pipes: "Check the rear side of pipes with a mirror and look for cracks and corrosion"; "Are pipes securely fixed to the wall?"; and "Are there any signs of staining or algae growth, or any washed-out mortar joints, on the wall behind the pipe?"⁴

The checklist says what to check and how often. It gives no method for clearing a gutter or a pipe. On reaching them, it says to "Use binoculars to check high level areas like the roof or chimney from the ground if safe access is not available."⁴ Its test of a gutter's slope, "pouring water into the gutter and checking that it drains away", puts you at the gutter, so on this course's reading it goes by the ladder rules below.

In the US

The University of Georgia's extension checklist, a spring and autumn list: "Clean gutters and downspouts (may need to be done more frequently). Make sure they discharge water 2-3 feet away from the house."³ The University of Minnesota Extension gives more: "Place a minimum of one downspout per 50 linear feet of roof eave. Extensions should discharge water at least 4 feet beyond the wall."²

The two figures differ, 2 to 3 feet against at least 4 (about 0.6 to 0.9 m against 1.2 m), and both come from US university extension services. Neither says why it chose its number, and this course will not guess. The honest rule is well away from the wall; your local extension service or building department may give a figure. Neither checklist gives a method for cleaning a gutter.

No British source this course read gives a distance for a downpipe's discharge. Historic England's checklist does list drainage gullies, the grated openings at ground level, for inspection "every autumn and preferably more often", checking that they are "free from silt, debris, vegetation and other objects" and that "all gully inlets are covered by a grating".⁴

The labels

Looking, from the ground and in the rain, is Yours. So is setting an extension or splash block at the foot of a downspout, on this course's reading: neither source says who does it, and it involves no height and nothing hidden, so it's yours if it's your home to repair, or your landlord agrees.

Clearing a gutter is Yours, on conditions, and the conditions are lesson 15's and lesson 16's. A ladder has to be the right equipment for the job at all. It needs to rest on something strong: HSE, Britain's Health and Safety Executive, says in its workplace guidance "do not rest it against weak upper surfaces such as glazing or plastic gutters".¹¹ It keeps to HSE's guide of no more than 30 minutes up a ladder at a time, and it stays out of HSE's 6 m from an overhead power line (lesson 15 gives OSHA's 10 feet, a US federal rule for employers, beside it).¹¹ A long run of gutter can fail the 30-minute guide on its own, as the gutter job in lesson 16's practice did, and then it's Call someone, or the job split into short spells with a fresh set-up each time (this course's reading of HSE's "at a time").

Historic England, writing for owners of older homes in England, has a page for people doing their own work, and it says ladders are "handy for clearing debris from gutters or doing a quick maintenance check". The next sentence is "Only use them to gain access, not as a working platform."¹⁵ It doesn't say how those two fit together, and this course won't guess. It also offers "someone else is holding it steady for you" as an alternative to tying the ladder, where HSE's order, in lesson 15, puts footing last. The label stays Yours, on conditions, with lesson 15's order.

One more condition comes before the ladder. HSE says asbestos "may be part of any commercial or domestic building which was built or refurbished before the year 2000", and lists "asbestos cement products (pipes, flues, roofs etc)".⁹ Its series of task sheets for trades includes one on "Cleaning debris from gutters on an asbestos cement (AC) roof", and that sheet says the gutter "may be made of AC, or it may simply collect water from an AC roof".¹⁰ Another covers removing "bituminous products, such as roofing felt, gutter linings or damp-proof courses" that contain asbestos (this course read that one's title only).¹⁰ So clearing debris from an asbestos cement gutter, or from any gutter under an asbestos cement roof, is on HSE's list of asbestos work. Its advice to householders: "Do not try to repair or remove any asbestos materials yourself if you have not had any training for non-licensed asbestos work."⁹ Historic England's page is shorter: "If you think there may be materials containing asbestos within your home you need to contact a specialist."¹⁵

In the US, EPA gives no date. It says you generally can't tell by looking, and "If in doubt, treat the material as if it contains asbestos and leave it alone."¹⁴ If your gutters, downpipes or the roof they drain might be asbestos cement, leave them alone and read lesson 19, "Asbestos, lead paint and radon: what not to disturb", first.

The ground against the wall

Water that reaches the ground next to a wall goes where the ground sends it. The two countries' sources describe this for different kinds of house, the US ones for basements and the British ones for a damp-proof course.

In the US: the slope

The University of Minnesota Extension: "If the ground around a foundation is level or slopes toward the house, water is directed into the basement. The soil next to the house is often backfilled without proper compaction and later settles."² So a house built with a good slope can lose it as the loose soil against the foundation settles. Its fix: "Place earth around the house so that it slopes away from the foundation wall a minimum of 1 inch per foot for at least 6 feet."²

Drawn to scale, the extension service's minimum is a gentle slope: 6 inches over 6 feet. The extension service gives no method for measuring it. Its order of work puts the outside first: "The recommended approach after removing interior moisture sources is to evaluate the gutters, downspouts and surface grading around the house. These should be corrected first and may solve the problem."²

Checking the slope is Yours. Moving soil in quantity, or relaying a path or patio, is a building job the extension service describes but doesn't give a householder a method for; it notes it "may require hauling fill to the site".² This course read nothing on digging near buried pipes and cables, so its label for regrading is Call someone (the course's reading).

In the UK: the damp-proof course

A British house built with a damp-proof course has a waterproof layer low in its walls. The Property Care Association (PCA), the trade body for damp-proofing firms, says it is "installed roughly at about 6 inches from the ground".⁵ Historic England's checklist gives the matching figure for the ground: "Check to ensure that ground levels are at least 150 millimetres below the level of any known damp-proof course or 150 millimetres below internal floor levels".⁴ (Six inches is about 150 millimetres; the two agree.) Historic England doesn't say why it wants 150 millimetres, and this course won't guess.

Ground or paving raised above the damp-proof course can let water past it. The PCA calls this bridging, and GOV.UK lists a "bridged (compromised) damp proof course" among its outside checks.¹ The PCA's list of common causes of rising damp opens with "Moisture by-passing over the damp proof course with higher ground levels around the base of the property", giving a patio or a planting area as its example. And its remedy for bridging is modest: "removing the ‘bridge’ should hopefully be sufficient to control the capillary rise of moisture in the wall".⁵ Note the "should hopefully": the trade body puts removing the bridge first, and doesn't promise it will be enough.

Historic England's base-of-wall list adds two more: "Ensure that vents are not obstructed" and "Remove plants and vegetation growing on or close to the building if they are causing damage".⁴ On this course's reading, the vents low in a wall are air bricks, which GOV.UK calls "a cost-effective and easy means of addressing inadequate under-floor ventilation".¹ Neither source tells you how to find a damp-proof course that isn't visible; Historic England says "any known" one.

So: checking the ground level, clearing soil or leaves from air bricks, and pulling off plants that are causing damage are Yours. Lowering a patio or a path is Call someone, on this course's reading, as in the US. Whether damp low on an inside wall is rising damp, and what's causing it, is lesson 18's question. GOV.UK calls rising damp "often misdiagnosed", and a bridged damp-proof course is an outside cause worth ruling out first.¹

Termites and woodworm

Dry ground at the foundation matters for a second reason. EPA's page on termites, a US problem in this course's sources, says to "keep the soil around the foundation dry through proper grading and drainage (including maintenance of gutters and downspouts)", and "Do not pile or store firewood or wood debris next to the house."¹² In Britain, a council heritage page calls wood-boring insects "a symptom of excess damp".⁷ Both are lesson 21's, "Pests: find the cause, then control it".

The roof and its flashing, from the ground

Neither checklist this course read defines flashing. From where both place it, it's the weatherproofing at the joints where a roof meets a chimney, a wall, a vent pipe or a skylight (this course's gloss). The University of Georgia's checklist: "Check flashing around the chimney, plumbing vent, skylight, and other joints to ensure it is securely fastened; repair as needed."³ Historic England asks "Are all flashings still fixed into the wall, chimney or roof covering?" and wants them "dressed down" and not "blown or moved away from the surface of the wall".⁴

For the roof itself, Historic England says to inspect pitched roofs "twice a year and after storms or high winds", with binoculars from the ground if you can't get safe access, and gives a check that needs nothing at all: "Debris on the ground will give an indication of roof problems". It asks about "loose, slipped, broken or missing slates or tiles", and about moss: "This could potentially block gutters and pipes or stop water running off the roof." Its other roof check is indoors: "Look for signs of dampness on ceilings or in loft spaces as a possible indication of roof leaks".⁴ Georgia's checklist adds trimming branches that overhang the roof.³ It gives no method, and this course gives none; if the job takes a ladder, lesson 15's rules apply.

Those checks are Yours, done from the ground, from a window and on the ceilings. Going onto the roof is not. This course teaches no roof work, and read no source that teaches a householder any. The guidance it did read is British and written for construction work, and it is stark. HSE: "All work on roofs is highly dangerous, even if a job only takes a few minutes." "Those carrying out the work must be trained, competent and instructed in use of the precautions required." And on what kills people: "almost one in five deaths in construction work involve roof work. Some are specialist roofers, but many are just repairing and cleaning roofs."⁸ HSE gives no year or source for that figure on the page, and it's about construction work, not householders. It also says "all roofs should be treated as fragile until a competent person has confirmed they are not."⁸

So repairing flashing, resetting a slipped tile and clearing a roof are Call someone. That label is the course's own scope decision, with HSE's workplace guidance as the reason. Georgia's "repair as needed" says what a roof needs, not who should do it.

Old solid walls

A wall can let water in, and it can also keep water in. In 2022 the Royal Institution of Chartered Surveyors (RICS), Historic England and the PCA signed a joint position statement, so surveyors, a conservation body and the damp-proofing trade body put their names to the same text. It defines "traditional" buildings as those "with solid walls built from permeable materials such as brick, stone, earth, timber and lime-based mortars, plasters and renders." Then the mechanism: "Traditional construction absorbs moisture but allows it to evaporate when conditions become drier. This is in contrast to modern construction, which relies on impermeable barriers to prevent moisture entering the fabric."⁶

On this course's reading of that definition, a waterproof skin on a wall that works by drying out can stop water that gets in some other way from leaving. A council heritage page in Suffolk, writing about historic buildings in its district, says: "The most common cause of damp in old buildings is impermeable outer finishes", naming "cement render, or modern paints".⁷ The statement lists "use of impermeable mortars in repointing and rendering" among the changes a surveyor should record.⁶ And it warns surveyors that moisture in such a building "may not be down to a construction failure".⁶

What you can do with this is look and record. Cracks in render are on GOV.UK's list of checks.¹ Historic England's checklist asks you to "Look for defects in stonework, brickwork and rendering".⁴ Whether an old wall's render or paint is part of its damp problem is a question for a surveyor who knows traditional buildings, and replacing render is Call someone, on this course's reading.

A damp patch under a gutter

A 1950s brick semi in the East Riding of Yorkshire has a damp patch high on a bedroom wall, in the corner under the eaves. It spreads after heavy rain and shrinks in dry spells. The owner's first thought is condensation, since the corner is cold.

Start outside, with Historic England's instruction: inspect while it is raining. On the next wet day the owner stands in the garden with a coat on and watches. The gutter above the bedroom overflows at one point, in a sheet, straight down the wall over the corner. That's Historic England's "Does rainwater cascade over the gutter from the roof?", answered yes.⁴ After the rain, from an upstairs window at the side, a clump of moss and leaves is visible in the gutter near the outlet.

The chain fits: blocked outlet, overflowing gutter, wall soaked from outside, and damp on the inside of that wall. It is the likeliest cause, not a proven one, and the next heavy rain after clearing it is the test. That's penetrating damp in GOV.UK's sense, a defect letting outside water in.¹ It may be making condensation in the corner worse, as the guidance says penetrating damp can.¹

Then the labels. The house was built in the 1950s, well before 2000, so the owner first checks what the gutter is made of, and what roof drains into it. It's plastic, and the roof above it is clay tiles, not asbestos cement sheets, so on this course's reading the asbestos cement question does not arise. That raises the ladder question instead: HSE says not to rest a ladder against a plastic gutter.¹¹ The gutter is at the eaves, above the upstairs windows, so the ladder needs a strong resting point below it, such as the stand-off device lesson 15 showed, and there's no overhead line within 6 m. The job is minutes, not an hour. So clearing that outlet is Yours, on conditions, the conditions being lesson 15's and 16's set-up rules. If the owner can't meet them, a gutter-clearing firm is the call. Either way, the next check is the same: watch again in the next heavy rain, and see whether the overflow has stopped and whether the patch starts to dry.

A wet basement in July

A 1960s house in the Finger Lakes region of New York State has a poured-concrete basement. Every July and August its walls and floor are damp to the touch, and in winter they're dry. The owners keep the basement windows open in summer to "air it out". A waterproofing contractor has looked and quoted for a coating on the inside of the walls.

The University of Minnesota Extension names exactly this: "In the summertime, basement windows may be opened for fresh air. If the outside air is warm and humid, it will condense on the cool basement wall and floor surfaces. Many homeowners see this moisture and believe they are experiencing basement wall leakage, when in fact the accumulated moisture is from condensation."²

Now the part the extension service doesn't settle for you, and the gap is yours to reason through. It gives no test for telling condensation from leakage, and its list of symptoms is not sorted by cause. It includes "Condensation on cold walls and floor in summer.", "Water trickling out of walls." and "Standing water on floor."² The timing is the clue it does give: its condensation case is a summer one, with the windows open.

The extension service says one more thing worth knowing before anyone sells you a machine: "Dehumidification can be used as a means of reducing the symptoms of humidity and odor in a basement, but it is not a permanent or complete solution."² It goes further: in a basement with moisture problems, it says a dehumidifier "may cause greater damage", because drying the air draws moisture in faster.² This course read no British source on cellars, so this section is the US's only.

What people get wrong

"A damp basement wall in summer means a leak." Often it's condensation from warm, humid air meeting cool walls, which the University of Minnesota Extension says many homeowners mistake for leakage.²

"A downspout that ends at the wall is fine." The extension service says one without an extender or splash block "is worse than no downspout at all".²

"Once a year is enough for any gutter." Historic England says at least every autumn "and preferably more often", and after heavy leaf fall. The University of Georgia says its "maintenance frequencies may vary depending on your local climate".⁴³ Historic England also asks "How is the building affected by nearby trees?"⁴ A house under trees needs more, on this course's reading.

"Damp low on a wall means the damp-proof course has failed." The damp-proofing trade body's own list of common causes of rising damp opens with ground or paving bridging the damp-proof course, and its first remedy is removing the bridge.⁵ Lesson 18 takes the rest.

"A dehumidifier fixes a wet basement." The extension service calls it "not a permanent or complete solution", and says in a basement with moisture problems it "may cause greater damage".²

Practice

For your plan

This lesson adds to the calendar: gutters and drainage gullies each autumn and preferably more often (Historic England; Georgia's spring and autumn), downpipes watched in heavy rain, and the roof looked over from the ground twice a year and after storms (Historic England). It adds to the map: where each downpipe discharges, the ground level at each wall, and any gutter, pipe or roof that might be asbestos cement. And it adds to the stop list: anything on the roof, any gutter you can't reach by the ladder rules, and any possible asbestos cement, including a gutter under an asbestos cement roof.

Connections

Lesson 4, "Water out: traps, vents and blocked drains", met the sump pump that lifts groundwater out of a basement; the University of Georgia's checklist lists checking that it works.³ Lessons 15 and 16 are the rules for the one job here that needs a ladder. Next, lesson 18, "Damp inside: condensation, mould, ventilation and rising damp", takes condensation, mould, ventilation and the argument about rising damp. Lesson 19 is where asbestos cement is taught, and lesson 21, "Pests: find the cause, then control it", picks up termites and woodworm.

Go deeper

• Historic England, "Maintenance Checklist", free. The fullest British list this course read for the outside of a house, written for older homes in England, in the order a walk-round takes.
• University of Minnesota Extension, "Moisture in basements: causes and solutions", free. Read here in full. Where basement water comes from and what to fix in what order, written for Minnesota basements.
• RICS, Historic England and the PCA, "Investigation of moisture and its effects on traditional buildings",
  2022. Read here in full. Sixteen pages written for surveyors; worth reading before you hire one for an old house, so you know what a proper investigation covers.

Sources

1. Department of Health and Social Care, Ministry of Housing, Communities and Local Government and others, "Understanding and addressing the health risks of damp and mould in the home", GOV.UK, first published 7 September 2023, updated 1 April 2026. Read: full body text through the GOV.UK content API, re-read 26 September 2026. Guidance for landlords and housing professionals in England.
2. J. Carmody, B. Anderson and R. Stone, "Moisture in basements: causes and solutions", University of Minnesota Extension, no date shown. Read: full text, re-read 26 September 2026.
3. P. R. Turner and L. Bailey, Home Maintenance Checklist, Circular 1082, University of Georgia Cooperative Extension, reviewed June 2021. Read: full text, re-read 26 September 2026.
4. Historic England, "Maintenance Checklist", published 25 July 2013, and "Essential Tips for Maintaining and Repairing Older Homes", published 19 July 2013. Read: full page text of both live pages, in a browser, 26 September 2026. Written for owners of older homes in England. The pages have moved and their wording has changed since the August 2023 Internet Archive captures (20230824101706 and 20230824101753) this lesson was first drafted from.
5. Property Care Association, "Rising Damp Advice". Read: full text, re-read 26 September 2026. The trade body for damp-proofing specialists.
6. RICS, Historic England and the Property Care Association, Investigation of moisture and its effects on traditional buildings: Principles and competencies, joint position statement, first edition, September 2022. Read: full text, re-read 26 September 2026.
7. Babergh and Mid Suffolk District Councils, "Wood-boring insects". Read: full text, re-read 26 September 2026. A council heritage page about historic buildings.
8. Health and Safety Executive, "Roof work", last updated 5 June 2026. Read: full text, 26 September 2026. Construction guidance for Great Britain.
9. Health and Safety Executive, "Asbestos: FAQs", updated 4 September 2025. Read: full text, re-read 26 September 2026. Great Britain.
10. Health and Safety Executive, "Asbestos essentials task sheets", updated 19 September 2025, and sheet a10, "Cleaning debris from gutters on an asbestos cement (AC) roof", 09/17. Read: the index page (sheet titles), and page 1 of sheet a10 for what it covers; the other sheets were not read. Written for building, maintenance and allied trades.
11. Health and Safety Executive, "Safe use of ladders and stepladders", web guide. Read: pages 1 to 7 on 25 September 2026; pages 2 and 4 re-read 26 September 2026. Guidance for workplaces in Great Britain.
12. US Environmental Protection Agency, "Termites: How to Identify and Control Them", last updated 21 October 2025. Read: full text, re-read 26 September 2026.
13. US Environmental Protection Agency, "A Brief Guide to Mold, Moisture and Your Home", last updated 18 February 2026. Read: full text.
14. US Environmental Protection Agency, "Protect Your Family from Exposures to Asbestos", last updated 25 June 2026. Read: full text, re-read 26 September 2026.
15. Historic England, "Keeping Safe When Working On an Older Home", updated 25 September 2025. Read: full page text, in a browser, 26 September 2026. Written for owners of older homes in England.