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BASEMENTATLAS · KNOWLEDGE MAP

Complete knowledge map

Browse guides, scenarios, checklists, comparisons, cases and technical terms about damp, drainage, ventilation, floors, foundations and basement renovation.

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BASEMENTATLAS · DAMP

Damp basement & water ingress

Treat the timing and location of moisture as evidence. Rain-linked damp, a wet wall–floor junction, salts and a persistent low-level moisture line can point to different mechanisms, so they should not be collapsed into one generic ‘damp basement’ diagnosis.

GuideDamp basement walls: find the cause before choosing a repairGuideWater through the basement floorGuideHow to document a basement problemGuideEfflorescence and salts on basement wallsGuideMeasuring basement moisture: a useful log, not just one numberGuideDrying a basement after water damageGuideBasement storage and moistureGuideMonitoring basement humidityGuideBefore-and-after documentation for basement projectsGuideWet basement floor after drainageGuideWet basement walls after drainageGuideRainwater entering a basementGuideWater at the wall-to-floor jointGuideEfflorescence returning after dryingGuideWaterproof slurry inside a basementGuideInjection damp-proofing in basement masonryGuideInternal basement waterproofingGuideBasement tanking systemsGuideRising damp in basement wallsGuideGroundwater below a basement floorScenarioBasement still damp after new drainageScenarioBasement floor wet but walls dryScenarioBasement wall gets wet after heavy rainScenarioSalts return after painting the basement wallScenarioBasement feels damp and cold but humidity readings look normalScenarioMonitoring basement humidity – appears after new windowsScenarioDamp basement wall – only one corner is affectedScenarioWater through the basement floor – starts after a new floor was installedScenarioWater through the basement floor – appears around a pipe penetrationScenarioRainwater entering a basement – appears after very heavy rainScenarioGroundwater below a basement floor – appears during snowmeltScenarioMonitoring basement humidity – gets worse when laundry dries indoorsScenarioDamp basement wall – remains even with a dehumidifierScenarioEfflorescence and salts on basement walls – is concentrated at the bottom of the wallScenarioEfflorescence and salts on basement walls – returns after cleaningScenarioDamp basement wall – starts after a new floor was installedScenarioDamp basement wall – appears around a pipe penetrationScenarioDamp basement wall – appears during snowmeltChecklistDamp basement inspection checklistChecklistBasement photo-documentation checklistChecklistBuying a house with a basement checklistChecklistChecklist: Before-and-after documentation for basement projectsComparisonVentilation vs DehumidifierComparisonExterior waterproofing vs Internal moisture controlComparisonDrainage only vs Drainage plus exterior waterproofingComparisonInterior wall insulation vs Exterior wall insulationProblemDamp or wet wallProblemWater on or through the floorProblemMould or black spotsProblemMusty or sewer smellProblemCondensation / summer dampProblemCracks or movementTechnical termCapillary-breaking layerTechnical termHydrostatic pressureTechnical termDew pointTechnical termRelative humidityTechnical termEfflorescence and salts on basement wallsTechnical termMonitoring basement humidityTechnical termGroundwater below a basement floorTechnical termRising damp in basement wallsTechnical termWaterproof slurry inside a basementConstruction profileDetached houseConstruction profileSemi-detached / duplexConstruction profileTerraced / row houseConstruction profileBrick / masonryConstruction profileConcreteConstruction profileStone / rubble masonryConstruction profileMixed / multiple materialsConstruction profileBefore 1930Construction profile1930–1959Construction profile1960–1979Construction profile1980–1999Construction profileUninsulated concrete basement slabConstruction profileTiled basement floorConstruction profileCoated or microcement basement floorConstruction profileBasement without perimeter drainageConstruction profileOlder perimeter drainage systemConstruction profileModern perimeter drainage systemConstruction profileNatural basement ventilationConstruction profileDehumidifier-led moisture controlConstruction profileHumidity-controlled basement ventilationConstruction profileBasement used for storageConstruction profileFinished basement room

BASEMENTATLAS · MOULD

Mould in basement & musty odour

Mould is an outcome, not a moisture diagnosis. The useful sequence is to identify the moisture source, remove or assess affected organic material, verify drying and only then choose the new wall or finish system.

GuideMould in a basementGuideMusty basement smellGuideMould behind a basement stud wallGuideMould behind furniture in a basementScenarioLaundry smells musty after drying in the basementScenarioCardboard or boxes mould on the basement floorScenarioMould appears behind a new basement wallScenarioMould in a basement – returns after cleaningScenarioMusty basement smell – is strongest when the house has been closedScenarioMould in a basement – only one corner is affectedScenarioMusty basement smell – gets worse when heating startsScenarioMould behind a basement stud wall – starts after wall insulation was addedScenarioMould in a basement – is concentrated near the ceilingChecklistChecklist: Mould in a basementComparisonMineral wall system vs Stud wallProblemDamp or wet wallProblemMould or black spotsProblemMusty or sewer smellProblemCondensation / summer dampCaseRoskilde, Denmark – hidden mould, mineral walls, radon detailing and ventilationConstruction profileBrick / masonryConstruction profileMixed / multiple materialsConstruction profileMechanical extract ventilationConstruction profileDecentralised heat-recovery ventilationConstruction profileBasement used for storage

BASEMENTATLAS · VENTILATION

Basement ventilation & condensation

Ventilation manages airborne moisture and pollutants; it does not stop liquid water through a wall or floor. In summer, more outdoor air can even increase condensation when the outdoor dew point is above the temperature of cold basement surfaces.

GuideBasement condensation in summer: when opening windows adds moistureGuideBasement ventilation or a dehumidifier: choose by the problemGuideHeat-recovery ventilation in basementsGuideHumidity-controlled basement ventilationGuideBasement indoor air qualityGuideCO₂ levels in basementsGuidePlacement of basement ventilation unitsGuideSizing heat-recovery ventilation for basementsScenarioBasement humidity is high only in summerScenarioVentilation makes the basement wetter in summerScenarioDehumidifier runs almost all the time in the basementScenarioCondensation forms on cold pipes in the basementScenarioBasement indoor air quality – remains even with a dehumidifierChecklistBasement ventilation installation checklistChecklistChecklist: Heat-recovery ventilation in basementsComparisonVentilation vs DehumidifierProblemMould or black spotsProblemMusty or sewer smellProblemCondensation / summer dampProblemRadon or new basement floorCaseBagsværd, Denmark – heat-recovery ventilation in a basementCaseHolbæk, Denmark – basement ventilation through a lightwellCaseRoskilde, Denmark – from dehumidifier to heat-recovery ventilationTechnical termDew pointTechnical termRelative humidityTechnical termHeat-recovery ventilation in basementsConstruction profile1980–1999Construction profile2000 and laterConstruction profileNatural basement ventilationConstruction profileMechanical extract ventilationConstruction profileDecentralised heat-recovery ventilationConstruction profileDehumidifier-led moisture controlConstruction profileHumidity-controlled basement ventilationConstruction profileBasement laundry or utility roomConstruction profileBasement bathroom useConstruction profileBasement workshop

A perimeter drain works as a system: water source, drain level, filter layer, inspection access, outlet and exterior waterproofing all matter. A new drain cannot compensate for an outlet that is too high or a wall detail that still admits water.

GuidePerimeter drainage around a basementGuideExterior basement waterproofingGuideMaintaining perimeter drainageGuideDimpled membrane on basement wallsGuideBasement drainage inspection chambersGuideDownpipes and water near basement foundationsGuideGround slope away from basement wallsGuideBlocked perimeter drainageGuideCorrect depth for perimeter drainageGuideDrainage gravel and filter fabricScenarioWater at exterior basement stairsChecklistPerimeter drainage quote checklistChecklistChecklist: Exterior basement waterproofingComparisonExterior waterproofing vs Internal moisture controlComparisonGravity drainage vs Pump systemComparisonDrainage only vs Drainage plus exterior waterproofingComparisonFloor drain vs Pumped drainageProblemDamp or wet wallProblemWater on or through the floorCaseDenmark – perimeter drainage, exterior waterproofing and reinstatementCaseBasement flooding after heavy rain: pumping and perimeter drainageTechnical termHydrostatic pressureTechnical termPerimeter drainTechnical termDrainage gravel and filter fabricTechnical termDimpled membrane on basement wallsTechnical termDrainage gravel and filter fabricConstruction profileDetached houseConstruction profileTerraced / row houseConstruction profileStone / rubble masonryConstruction profile1930–1959Construction profileBasement without perimeter drainageConstruction profileOlder perimeter drainage systemConstruction profileModern perimeter drainage systemConstruction profileGravity drainageConstruction profilePumped basement drainage

BASEMENTATLAS · EXCAVATION

Basement excavation & lowering the floor

Lowering a basement floor changes more than ceiling height. Foundation depth, temporary support, groundwater, sewer levels, radon detailing and the final floor build-up must be considered as one sequence before excavation starts.

GuideBasement excavation and floor loweringGuideBasement renovation sequence: what to resolve before the finishesGuideBasement renovation cost: build a budget from the actual scopeGuideBasement renovation timelineGuideBasement ceiling heightGuidePermits and local rules for basement renovationGuideCompare basement renovation quotes: a scope checklistChecklistBasement excavation quote checklistComparisonLower the basement floor vs Keep the existing floor levelComparisonLarger basement window vs Direct basement exitComparisonPhased renovation vs Full renovationProblemCracks or movementProblemLow basement / lower the floorCaseVirum, Denmark – complete basement renovation from excavation to finished roomsCaseDenmark – converting a crawlspace into basement rooms with direct stairsCaseCentral Copenhagen – complete renovation of a former basement shopCaseCharlottenlund: a basement lowered 120 cm with new garden accessTechnical termUnderpinning

BASEMENTATLAS · FOUNDATION

Underpinning & foundation strengthening

Foundation work is controlled by load paths and sequence. Existing footing depth, soil and groundwater conditions, crack patterns and the size of each working section can change what is safe to excavate or underpin.

GuideBasement underpinningGuideCracks in basement wallsGuideFoundation settlement around a basementGuideMonitoring basement cracksGuideBasement contractor scope and handoverGuideCrack injection in basement wallsScenarioA basement crack is getting widerScenarioCracks appear after basement excavationChecklistUnderpinning planning checklistChecklistChecklist: Monitoring basement cracksComparisonDIY work vs Professional contractorProblemCracks or movementProblemLow basement / lower the floorCaseAmager, Denmark – excavation, sectional underpinning and complete basement renovationCaseSjellonlund, Denmark – floor lowering and underpinning as a partial contractTechnical termUnderpinningConstruction profileDetached houseConstruction profileSemi-detached / duplexConstruction profileTerraced / row houseConstruction profileApartment buildingConstruction profileConcreteConstruction profileBefore 1930

A basement floor is a layered moisture, thermal and structural system. Capillary break, insulation, airtight/radon details, services, concrete or screed drying and the finish must work together rather than being chosen as separate products.

GuideNew basement floorGuideCracks in concrete basement floorsGuideUnderfloor heating in a basementGuideBasement ceiling insulationGuideInsulation below a basement floorGuideVapour and air barriers below basement floorsGuideDrying concrete and screed in basementsGuideTiles on basement floorsChecklistNew basement floor planning checklistChecklistChecklist: Insulation below a basement floorComparisonLower the basement floor vs Keep the existing floor levelComparisonUnderfloor heating vs RadiatorsProblemWater on or through the floorProblemLow basement / lower the floorProblemRadon or new basement floorCaseSøborg, Denmark – from raw basement to a new tiled floorTechnical termCapillary-breaking layerTechnical termVapour and air barriers below basement floorsTechnical termUnderfloor heating in a basementTechnical termDrying concrete and screed in basementsConstruction profile1930–1959Construction profile1960–1979Construction profile1980–1999Construction profile2000 and laterConstruction profileUninsulated concrete basement slabConstruction profileInsulated basement slabConstruction profileBasement floor with underfloor heatingConstruction profileTiled basement floor

BASEMENTATLAS · RADON

Radon in basement

Radon decisions should be measurement-led. Establish the baseline, understand likely entry paths through floor joints and penetrations, choose mitigation that fits the construction, and measure again after the work.

GuideRadon in basementsGuideMeasuring radon in a basementGuideRadon depressurisation below a basement floorScenarioRadon is high after a basement renovationChecklistChecklist: Measuring radon in a basementProblemRadon or new basement floorTechnical termRadon membraneConstruction profile2000 and laterConstruction profileInsulated basement slab

A basement bathroom combines wet-room loads with basement moisture risk. Drainage, waterproofing, penetrations, ventilation, floor levels and the surrounding construction should be planned together before finishes are selected.

GuideBasement bathroomGuideBasement sump pumpGuideSewer smell in a basementGuideBasement floor drainsGuideBackwater valves in basementsGuideReplacing basement sewer pipesGuideBasement laundry roomsGuideSump pump maintenanceGuideCamera inspection of basement sewer pipesScenarioBasement floor drain smellsScenarioSewer backs up during heavy rainScenarioBasement sump pump – appears when the pump stopsScenarioBasement laundry rooms – gets worse when laundry dries indoorsScenarioSewer smell in a basement – is strongest when the house has been closedScenarioSump pump maintenance – appears when the pump stopsChecklistBasement bathroom planning checklistChecklistChecklist: Sump pump maintenanceChecklistChecklist: Backwater valves in basementsChecklistChecklist: Basement bathroomComparisonGravity drainage vs Pump systemComparisonFloor drain vs Pumped drainageTechnical termSump pumpTechnical termSewer backflowTechnical termBackwater valves in basementsTechnical termBasement floor drainsConstruction profileSemi-detached / duplexConstruction profileApartment buildingConstruction profileGravity drainageConstruction profilePumped basement drainageConstruction profileBasement laundry or utility roomConstruction profileBasement bathroom use

A larger basement opening affects daylight, structure and water management at the same time. Lintel/support, exterior ground level, lightwell or stair drainage and the final sill/threshold detail all influence the result.

GuideBasement windows and daylightGuideDirect basement exitGuideBasement stairsGuideExterior basement stairs and drainageGuideCondensation on basement windowsGuideBasement window-well drainageGuideDrainage at basement door thresholdsGuideCovers for basement window wellsGuideEnlarging a basement window openingScenarioWater collecting in a basement window wellScenarioCondensation on basement windows – gets worse when heating startsScenarioCondensation on basement windows – appears after new windowsScenarioBasement window-well drainage – appears after very heavy rainChecklistChecklist: Basement window-well drainageChecklistChecklist: Enlarging a basement window openingComparisonLarger basement window vs Direct basement exitCaseValby, Denmark – from small basement window to double doors and direct exitTechnical termDew pointTechnical termBasement lightwellTechnical termThermal bridgeTechnical termBasement window-well drainage

BASEMENTATLAS · MATERIALS

Basement walls, insulation & finishes

Basement finishes should be chosen from the moisture behaviour of the existing wall, not from appearance alone. Substrate condition, salts, drying direction and the amount of organic or vapour-tight material in the build-up can change the risk.

GuideMineral basement wall systemsGuideRenovating an old basementGuideThermal bridges in basementsGuideInsulating basement wallsGuidePlaster for basement wallsGuidePaint for basement wallsGuideDIY or professional basement workGuidePeeling paint on basement wallsGuideCrumbling plaster on basement wallsGuideOld stone basement wallsGuideBrick basement wallsGuideConcrete basement wallsGuideCalcium-silicate boards in basementsGuideLime plaster in basementsGuideSilicate paint for basement wallsGuideRepointing basement masonryGuideMicrocement in basementsScenarioPaint peels mainly at the bottom of the basement wallScenarioInsulating basement walls – starts after wall insulation was addedScenarioThermal bridges in basements – is concentrated near the ceilingScenarioPeeling paint on basement walls – is concentrated at the bottom of the wallChecklistBasement renovation handover checklistChecklistChecklist: Renovating an old basementChecklistChecklist: Paint for basement wallsChecklistChecklist: DIY or professional basement workComparisonMineral wall system vs Stud wallComparisonInterior wall insulation vs Exterior wall insulationComparisonUnderfloor heating vs RadiatorsComparisonPhased renovation vs Full renovationComparisonDIY work vs Professional contractorCaseBrønshøj, Denmark – mineral walls and specialist finish without floor loweringCaseGentofte: repairing the render in an existing basement stairwellTechnical termCapillary-active wall systemTechnical termThermal bridgeTechnical termInsulating basement wallsTechnical termLime plaster in basementsTechnical termSilicate paint for basement wallsConstruction profileApartment buildingConstruction profileBrick / masonryConstruction profileConcreteConstruction profileStone / rubble masonryConstruction profileMixed / multiple materialsConstruction profileBefore 1930Construction profile1960–1979Construction profileBasement floor with underfloor heatingConstruction profileCoated or microcement basement floorConstruction profileBasement workshopConstruction profileFinished basement room
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