Buying a home – different foundation types

foundation types

Different foundation types have different maintenance considerations.  Foundation systems of all types depend on the integrity of the supporting soil to prevent settling over the long-term.  In our geographical area clay is the predominant supporting soil type.  Clay is more susceptible to expanding and settling than other types like silt, sand, loam, or rock which is why managing the water around the home is even more important in our area.  Water/moisture is the enemy of all foundation types and in all cases it is important that the grading and drainage is properly installed and maintained to prevent structural damages and settling over the long-term.


Basements are full height foundations below the ground.  Buying a house with a basement is a great opportunity for increased finished living areas, semi-finished areas, or un-finished storage areas.  Basements in flatter regions are below ground at all 4 sides.  Basements in hilly or mountainous regions like ours tend to be ‘daylight’ basements where water damages tend to manifest at the uphill side.  Basement foundation walls tend to develop more structural issues than crawl spaces because taller basement foundation walls tend to retain more earth.

Sloping Sites

In our area it is common to have ‘daylight’ basements with one wall nearly entirely below grade and an opposite wall that is partially or entirely above grade (with windows, doors and ‘daylight’).

Uphill or retaining foundation wall

The uphill side of the foundation is retaining the lateral forces of the earth and the hydrostatic pressure of water.  Grading and drainage issues will often manifest themselves in basements on the retaining wall side, or the uphill side of the house.  Over time water pushes itself through the foundation wall, weakens it, and can eventually cause cracks and structural movement.  Evidence of water damage to the foundation wall can manifest as stepping or vertical cracks and dark water stains or white salts being pushed through the masonry.   Horizontal cracks often imply that the wall is buckling and leaning and is one of the most serious kinds of cracks.

Downhill or ‘Daylight’ foundation wall

The daylight side of the basement is typically less problematic as the grade generally slopes away and directs water away from the foundation walls.  Sometimes the daylight, or downhill, side of the house will manifest signs of settling because the foundation was installed too close to a steeply sloping grade or the wall was installed over loose fill or unsuitable soils.

Finished basements

Finished basements are heated and finished living areas where the foundation walls are partially or entirely hidden by finishes.  Sometimes these finishes can hide defects such as structural issues, water penetration and mold.  The inspection of finished basements is very limited but a good inspector will evaluate the baseboard trim at the basement perimeter looking carefully for evidence of water penetration.   As a maintenance prevention all grading and drainage observations in an inspection report should be repaired whether or not water penetration was observed in the basement.  Buyers of finished basements are often paying full retail for these heated and finished areas and ideally they are able to anticipate possible renovations/repairs before purchasing– for this reason it is important to hire an experienced inspector that can recognize signs of possible water damage in a finished basement.  In some cases, issues can only be discovered through seller disclosure– when it comes to finished basements it is always recommended to ask the seller about the history of issues, repairs or renovations.

Un-Finished basements

One advantage of buying a house with an un-finished basements is that the foundation walls are more accessible and buyers are better able to anticipate repairs before purchasing.  Ideally the foundation walls should be dry, cracks should be sealed and any structural issues should have had been monitored or repaired as directed by a structural engineer.   When sellers can not provide any additional documentation about structural damages observed in an inspection report a structural engineer should be consulted before purchase for further evaluation.  In our area, unheated and un-finished basements should have some sort of de-humidification system in place to control moisture during the warmer/rainier months.

Crawl Spaces

Homes over crawl spaces are supported by the perimeter foundation wall and the piers under major beams– it is important to direct water away from both the foundation walls and the pier footing areas to prevent structural issues over the long-term.

Crawl spaces should be dry, well ventilated, clean of debris, and have good inspection, maintenance and repair access to all areas- especially plumbing areas.  Maintaining the crawl space environment starts outside as all water should be directed away from the foundation areas with proper grading and drainage (gutter systems).  Crawl spaces tend to have less foundation walls issues than homes with basements but more issues with humidity– long-term moisture issues are indicated by stringy insulation, wet/muddy areas, standing water, fungus, wood destroying insects and high moisture content at the framing.  For this reason most crawl spaces, especially in our geographical area, will need ventilation or de-humidification upgrades or repairs over time.

Excavated crawl spaces

In our area it is common to see ‘dug-out crawl spaces’ or sometimes they are called ‘dug-out basements’– I generally prefer the term excavated crawl spaces because they usually have exposed soil either at the ground or walls and therefore have more in common with crawlspaces.  These ‘dug-out’ foundation areas were originally crawl spaces that were later excavated to provide better access.  Excavating the supporting soil near foundation walls and pier footings compromise the structure- especially when retaining walls are not put into place to support the excavated areas.  Excavated crawl spaces maintain their shape without retaining walls because of the red clay soil that is typical of our region.  Water penetration from the outside can cause erosion and will compromise the supporting soil and walls/piers over the long-term.  Excavated crawl spaces are very common in our region however it is always best practice to follow up with a general contractor or structural engineer about repairs to prevent structural issues.

‘Finished’ Excavated crawl space (finished basement attempt)

A properly installed finished basement should have a thick floor slab and full height foundation wall with water proofing on all sides but occasionally we will inspect a house where the owner has attempted to ‘finish’ a crawl space.  The sellers will call them ‘finished basements’ but they do not have proper slabs or foundation walls and therefore are prone to water damage, rot and air quality issues.  There are too many issues with these ‘finished basements’ to go over here but they should be considered temporary and buyers should not be expected to pay full retail for these ‘heated and finished areas’.  More than likely many of these finishes will need to be removed and expensive structural repairs will be needed before making these area habitable without mold/decay.

Slab foundations

Homes built over concrete slabs do not have basements or crawl spaces but are supported by the slab and the supporting soil beneath– because the footings are so shallow it is important to prevent erosion near slab foundations.  It is also still important to follow up with all grading/drainage concerns to prevent the slab from cracking and settling over the long-term because failing slab foundations can be difficult and expensive to repair.  Slab foundations are generally not a good option at steep sites which is why they are less common in mountainous areas but they are more common at condo/townhome communities and flatter regions.

Patio/garage slab additions

We also see a lot of additions built over slabs, especially over existing patios, porches and garages.   It is important to keep in mind that these slabs are not built to the same specifications as properly built slab foundations intended for finished/heated areas.  Patio slabs are often thinner (no thickened slab at bearing walls and point loads), un-insulated, do not have water-proofing or electrical/plumbing/HVAC conduits provided.

Pier Foundations

Pier foundation systems are more commonly found in flood and hurricane areas.  In our area we see more pier foundation systems near lakes and rivers.  It is important to direct all water away from pier footing areas to prevent settling.

Porch/deck additions

Deck framing is often considered temporary and is expected to have about a 25 year life expectancy.  Building a ‘permanent’ addition over deck-framing can present long-term issues.  Deck framing is designed to slope away from the home and is built to different specifications than finished floor framing.  Decks and porches commonly have wood/grade contact at the deck supports which is acceptable for a 25 year structure but the posts may decay and settle over longer time spans.  Ideally supporting posts for additions should have concrete footings that extend below the frost line and 8″ above grade– there should always be at least an 8″ clearance between the ground and wood framing.  These porch deck additions may not have central heating/cooling or good access to the floor or roof framing.  Often these porch additions are un-permitted structures built by the owners or un-licensed DIYers which is why it is common to also find electrical, plumbing and other defects.

Manufactured homes

Manufactured homes tend to be built on a pier and tie-down system– more on those here.

Asheville Foundation Inspector

Builder Buddy is your resource for Pier Foundation Inspections, Porch Addition Inspections, Deck Addition Inspections, Dug-out Crawl Space Inspections, Dug-out Basement Inspections, Excavated Crawl Space Inspections, Patio Addition Inspections, House on Piers Inspections, Unpermitted addition inspection, Garage Addition Inspections, Basement Inspections, Crawl Space Inspections, Finished Basement Inspections, and Unfinished Basement Inspections. Schedule online or call with questions.

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