Moisture, insects, structural problems...

The Old House Web

Editor's note: This story is adapted from theU.S. Department of Housing and Urban Development's Residential RehabilitationInspection Guide, 2000. Clickhere for other stories in this series.

inspecting basements

Clues to water problems include: wall cracks and stains, continuously working dehumidifier, rust at the base of support columns, peeling paint, white or dampness on walls, floor, stains or efflorescence, loose floor tiles, rot, items stored off the floor and water-damaged items, rusty baseboard nails, and patched walls.

Following the inspection of the site and the building'sexterior, move indoors and systematically inspect all interior spaces, includingthe basement or crawl space, finished rooms, halls and stairways, storagespaces, and attic.

Begin either at the lowest level and work up or at the attic and work down.

Examine the overall quality and condition of the building's constructionand finish materials. If the interior has unique woodwork or other stylisticfeatures, consider how these may be incorporated to best advantage in thebuilding's reuse.

Look for patterns of water damage or material deterioration that indicateunderlying problems in the structural, electrical, plumbing, or HVAC systems.These systems will be inspected separately after the interior inspection hasbeen completed.


crawl space
An uncovered earth floor in a crawl space can contribute a significant amount of moisture to a house -- up to several gallons per day. A vapor barrier such as 6 mil polyetheylene should be laid down, sealed at the edges and joints and ballasted with gravel.

The basement or crawl space is often the most revealing area in the buildingand usually provides a general picture of how the building works. In most cases,the structure is exposed overhead, as are the HVAC distribution system, plumbingsupply and DWV lines, and the electrical branch circuit wiring.

One of the most common problems in small residential structures is a wetbasement. Examine walls and floors for signs of water penetration such as:

  • dampness,
  • water stains,
  • peeling paint, efflorescence, and
  • rust on exposed metal parts.

In finished basements, look for:

  • rotted or warped wood paneling and doors,
  • loose floor tiles, and
  • mildew stains.

Determine the source of any moisture that may be present. It may come:

  • through the walls or cracks in the floor,
  • from backed-up floor drains,
  • from leaky plumbing lines, or from
  • a clogged air conditioner condensate line.

If moisture appears to be coming through the walls:

  • Re-examine the roof drainage system and grading around the exterior of the building (the problem could be as simple as a clogged gutter).
  • Recheck the sump pump, if there is one, to be sure the discharge is not draining back into the basement.
  • Look for unprotected or poorly drained window wells, leaking exterior faucets, and signs of leakage in the water supply line near the building.

Check the elevation of an earthen floor in a crawl space. If the water tableon the site is high or the drainage outside the building is poor, the crawlspace floor should not be below the elevation of the exterior grade. If thebasement or crawl space is merely damp or humid, the cause simply may be lack ofadequate ventilation, particularly if the crawl space has an earthen floor.

Check the ventilation. By measurement and calculation, compare the free areaof vents with the plan area of the crawl space. The free vent area to crawlspace area ratio should be 1 to 150 in a crawl space with an earthen floor and 1to 1,500 in a crawl space with a vapor barrier of one perm or less over theearthen floor. If the calculated ratio is less, consider adding ventilation,particularly in hot and humid climates, and especially if moisture is present.

Check the location of the vents through the foundation or exterior wall.There should be one vent near every corner of the crawl space to promotecomplete air movement. Check vents for screens. They should have corrosionresistant mesh in good condition with maxi-mum 1/8-inch (3.2 mm) openings. Ifthe ventilation appears to be inadequate and additional vents cannot be cut inthe foundation or exterior wall economically, consider adding a vapor barrierand mechanical ventilation.

Fungal and insect infestation

insect damage
Termite infestation is most common in basements and crawl spaces, particularly near foundation walls. Probe all suspect areas thoroughly. 

Look for signs of fungal growth on wood, particularly in unventilated crawlspaces. Termite infestation is most common in basements and crawl spaces,particularly near foundation walls. Probe all suspect areas thoroughly.

Inspect all foundation walls, piers, columns, joists, beams, and sill platesfor signs of termites and other wood inhabiting insects.

Thermal insulation

Examine the amount and type of insulating material, if any, above unheatedbasements and crawl spaces. Determine the amount of insulation required for thespace and whether additional insulation can or should be added. Check foradequate vapor barriers.

Structural, electrical,plumbing, and HVAC systems

Understand enough about the layout of each system to make an informedinspection of the remainder of the building's interior. A more completeassessment of these systems will be performed later.

  • Note the type of structural system (wood frame, masonry bearing wall, etc.).
  • Locate main support columns and posts, major beams, and bearing walls.
  • Find the main electrical panel box, if it is in the basement, and note how the branch circuits are generally distributed. Note also the type of wiring that is used.
  • Trace the path of the main water supply line and check the composition of all piping materials.
  • Observe the general location of the heating/cooling unit, if it is in the basement, and the general layout of the HVAC distribution system.
  • Locate the access to the crawl space, check that it is large enough for a person to enter, observe the interior of the crawl space, and if mechanical equipment is located inside, check that access is large enough for any required maintenance.

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