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The Potential PERILS of a Finished Basement

While inspecting a home, the basement is one of the most important areas to inspect. While there are many issues that can occur in basements - moisture, water entry, or flooding are one of the biggest (and potentially costly) issues I find.

An unfinished basement is ideal for an inspection. With the foundation walls, framing, and wires/pipes/ducts all exposed - you can see everything that is going on -- and maintain or repair any issues easily in the exposed areas. Finishes on ceilings can hide framing, wiring and more. Finished foundation walls can potentially trap moisture, hide foundation issues (such as cracks, water signs, spalling, joint damage AND MORE). When looking at a home with a finished basement - one concern should always be remembered - ALL FINISHED BASEMENTS HAVE THE POTENTIAL FOR HIDDEN WATER ENTRY ISSUES, CONDENSATION IN AND BEHIND WALLS, AND A POTENTIAL FOR HIDDEN INSECT DAMAGE (such as termites).

First, lets discuss basement finish materials:

Basement Finish Systems (Removable water-resistant panels that cover basement walls) are the best type of finish - as they:

  1. Can be removed for inspection or repairs.

  2. Most basement finish systems are made of materials that DO NOT ABSORB WATER and are typically not damaged when seepage or flooding occur.

  3. Most of these finish materials do not support growths (such as mold). If anything grows on their surfaces - the panels often can be cleaned/dried and re-installed.

Sheetrock or Plaster Walls (typically the LEAST desirable basement finishes) are less desirable as they often:

  1. Absorb water! Water penetrations can absorb into the material - often requiring repair or replacement when the walls are exposed to water.

  2. Grow Mold (and other growths). Sheetrock, plaster, and even old plaster wood lathe boards will typically support molds and other growths - AND OFTEN NEED REMOVAL OR REPLACEMENT WHEN THIS OCCURS.

  3. Can host HIDDEN Woodboring insects (such as termites) - as these walls are often framed with wood framing - which is often against floor and foundation areas (where subterranean Termites can enter the basement from).

Wood or Fiberboard Paneled Walls (Another less desirable finish):

  1. Moisture will often warp or delaminate these finish materials. While this is a cosmetic issue - such damage can be an indicator of other hidden issues.

  2. Paneling can easily grow mold and other such growths. Wood (and to a greater extent - fiberboard) panels are typically porous and easily allow mold to grow on and in the materials when enough moisture is present.

  3. Woodboring insects can attack and consume wood or fiberboard paneling. (For some reason - termites have seemed to cause more damage in the fiberboard paneling when I have seen the two types side by side with termite damage)

What about the floor?

First, it's important to discuss the differences in basement slab construction. Pre-1960's basement floor slabs often did not have any vapor barrier (a sheet of plastic designed to prevent moisture from migrating through the concrete) and the slab itself often acts as a moisture source since the moisture in the ground under it can pass right through it (often paint on slabs like this tends to peel off leaving salts behind as the water migrates through an evaporates into the home). Basement slabs without vapor barriers should be sealed with epoxy type paints, sheet vinyl flooring, or even better - ceramic floor tiles. This will help keep most of the moisture (or radon) sealed out of the basement.

Perhaps the best type of basement floor slab would be a concrete slab with a vapor barrier and two to four inches or more of foam insulation boards under the slab - sometimes with radiant heat built right into the concrete. This type of construction prevents the most moisture and condensation issues that are common with basement slabs.

AVOID WALL TO WALL RUGS ON FLOORS IN BASEMENTS! This is due to one very big reason: RUGS GAN GROW MOLD EASILY AND ARE INSTALLED DIRECTLY ON THE COLD SLAB SURFACE - Often leading to CONDENSATION and growths on/in the rugs. Area rugs (that are periodically taken out and professionally cleaned/sterilized) are a much better option. (This is less important for those rare few who have radiant heat in their basement floor slab - as the slab remains warm and condensation typically does not form as easily thus preventing the moisture that causes growths)

AVOID FIBERBOARD FLOORS IN BASEMENTS. These type floors are highly susceptible to warping/swelling when exposed to water or moisture. Wood floors have slightly less of a potential for this. I recommend that floor materials be NON-ABSORBANT (such as stone, ceramic tile, vinyl, etc.)

Built Up Floors (Floors "built up" with wood "sleepers" and plywood or OSB over them that raises the floor off the slab) pose their own potential issues:

  1. These areas are usually inaccessible, and like with other basement finishes - damage can become extensive before it is discovered.

  2. These areas often trap moisture and are much more prone to rot, mold, and insect damage.

  3. These areas can hide water entry - as water can actually be below the floor with NO VISIBLE EVIDENCE of this! Building a floor up DOES NOT CORRECT A WATER PROBLEM - IT ONLY HIDES IT!

While I consider finishes to be more detrimental than positive in below grade basement areas - there are ways to minimize the potential risks. I recommend that when finishing basement areas people consider the following:

  • Use REMOVABLE finishes whenever possible. Any finish which is fixed in place would have to be removed and re-installed (often costly) whenever repairs, inspections, or further evaluation is needed. Very often these permanent finishes are NEVER opened - and damage behind a finished wall can become extensive before it is discovered and repaired!

  • Use Non-absorbent materials (hydrophobic - or non-water absorbing - such as vinyl, closed-cell foam, fiberglass, non-corrosive metals or other such materials). Anything that absorbs moisture can also often grow mold. For example: ceiling tiles that are mineral fiber will often sag or grow mold when exposed to excessive moisture in the air - while plastic coated fiberglass panels do not tend to do this.

  • Install a FULLY SEALED drain system for both the floor and foundation walls. Drain systems are often POORLY installed with open holes in them. THE DRAIN SYSTEM NEEDS TO BE SEALED AIR-TIGHT! Moisture (AND RADON) will often enter the basement through the open drain system INCREASING MOISTURE AND/OR RADON LEVELS IN THE BASEMENT! I have found that MANY homes with open drain systems also had mold growths (and not just in basement areas - attics and other areas too!) and

  • Make any raised floor areas Accessible. If you do desire a "built-up" floor - you should consider making the floor removable in sections (such as 2 foot x 2 foot removable "panels") so that the floor can be pulled up and the areas under it checked for issues such as water/condensation, growths like mold, and rot or insect damage.

In conclusion:

If you have to finish your basement, these tips can help to prevent many common basement perils... I've seen far too many basements (including in modern/newer homes) that have expensive damage from water, growths such as mold, and wood boring insect activity - especially termites.

When you're installing a new finish in your basement, or you are repairing / opening up / replacing basement finishes - be smart... and reduce your risk of the most common basement problems.


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