Interior
air gap membranes are very often used in
conjunction with this system to eliminate moisture vapour penetration through
basement concrete
floors or walls.
Many concrete basement floors are not
constructed with a vapour barrier under them to stop the transmission
of moisture into the basement airspace. This will cause higher
than normal moisture levels in the basement and increase condensation
on anything cold. This problem needs to be addressed by managing
the humidity level with dehumidifiers and proper air circulation etc.
or the installation of a new sub-floor which includes an air gap
vapour barrier. This sub-floor system will greatly reduce the
moisture problem and give you a warm floor as well.
When installed over an existing concrete floor and
a new concrete slab is poured over top, we refer to these systems as
between slab drainage systems. Usually installed because the
original floor was installed too low or without a vapour barrier under
the slab. Of course we need to drain these Between Slab Drainage
Systems "BSDS" into something, usually an interior weeping tile or a
custom setup.
The
Dricore subfloor system that is purchased
through Home Depot is not used in high moisture areas, it is not
designed to function as a between floor drainage system. These
custom systems can be installed in with 1/2" spruce plywood to
accommodate carpet, or the stronger 5/8" T&G for special floor
coverings or just because you like the best.
Call 705-728-3476 for details.
Here is a link to more information on basement
moisture problems from the University of Minnesota
A note from Rod...
It seems that some "old school" contractors can't seem to wrap their head
around this application; don't be led down the wrong path by a company
that doesn't implement new and better technology. Simply put,
these systems work!
However, some circumstances about your building or location may indicate
that this system is not the first or best choice. A proper review of
your situation is always needed prior to determining the best system to
solve your particular problem.
Your contractor needs to have specific knowledge of all systems
to make the best judgements.
If you didn't follow the link above, here is some great info from the
University of Minnesota the explains the differences in the interior
drainage systems.
APPROACH 1:
RECOMMENDED
Install Proper Gutters and Downspouts and Correct Grading
A great number of basement water problems can be solved by handling rainwater and surface drainage properly using gutters and downspouts with extenders or splashblocks to carry the water away from the foundation. Sloping the grade away from the house, which may require hauling fill to the site, is very important. This should be done before any below-grade drainage system is installed, since the above-grade corrections may solve the problem. Even if a drainage system is required, removing water at the source as much as possible is necessary.
APPROACH 2:
RECOMMENDED (see our
excavation services page)
Exterior Drainage System
Installing an exterior drainage system at an existing building is the most costly, but also the most effective water control approach. This requires digging up the area around the foundation and rebuilding it similar to a new house installation. It also requires digging up shrubs and other obstacles around the house.
Usually, waterproofing and insulation are installed at the same time, in addition to making any repairs to the structure. The traditional exterior drainage systems use free-draining sand in the backfill. Drain tile can be placed beside or on top of the footing. Level drain pipe installations are satisfactory. A minimum of 12 inches of coarse aggregate should be placed around the drain tile.
Free-draining Membrane or Board
It can be expensive to haul clear stone or sand to a site for backfilling purposes. Instead, a drainage mat can be placed against the foundation wall and then backfilled with any soil on site. The drainage must have a free-flowing path to the perforated drain pipe below.
Draining to a Sump
All exterior drainage systems must drain to a sump that can be pumped out. The sump must have an airtight, childproof cover.
APPROACH 3:
BY Johnson Group Contracting
Interior Drainage Channel above the Concrete Slab
In most cases when water is entering the basement, an interior drainage system is installed. The simplest and least costly approach is a drainage channel adhered at the base of the wall and the floor slab. Water is collected and drained into a sump using another channel placed on top of the slab, then through a trap to the sump basin. The sump should have an airtight, childproof cover. This system is best suited to a concrete wall with cracks.
It does not solve the problem in masonry walls because water remains in the block cores at floor level and the water level is only lowered to the top of the slab. With this approach, the water is not completely removed from the space. The result is that humidity, mold, and mildew can still be a problem. This system cannot drain groundwater from under the floor slab.
APPROACH 4:
BY Johnson Group Contracting
Interior Drainage Channel within the Slab Edge
Another technique is to place a drainage channel at the base of the wall on top of the footing. This requires removing and then replacing the concrete along the slab edge. The drainage channel is connected to a drain pipe leading to the sump. The sump should have an airtight, childproof cover. This approach is effective for concrete masonry walls with water problems because it drains the block cores completely. Holes must be drilled at the base of every block core to permit drainage. This may require removing more than the minimum amount of concrete, as shown, to fit the drill in. These systems have different shapes and prices depending on the product installed. Because moisture is allowed to penetrate the block cores, it is essential to cap the tops and place an air-vapor barrier on the wall.
From Johnson Group: This system cannot drain groundwater from
under the floor slab. Water can fill up under the floor to the height of
the drainage channel causing a cold floor, vapour transfer in the home
and wicking of water up through floor cracks.
APPROACH 5:
RECOMMENDED Our
choice for interior applications!
Interior Drainage System Beneath the Slab
The most effective of the interior drainage systems is a perforated drain pipe installed inside the perimeter of the footing. This requires removing and replacing concrete at the slab edge. By placing the drain pipe beneath the slab, it drains the area to a lower level. Similar to an exterior system, the drainage pipe connects to a sump. The sump should have an airtight, childproof cover. A critical component of this approach is the dimpled plastic sheeting placed at the base of the wall and beneath the slab edge. Dimpled sheeting is similar to a small egg crate and permits free drainage down the wall and across into the drain pipe. It is less expensive than many specialized drainage channel systems. In low permeability soils, this system cannot accept rising groundwater unless there is an aggregate layer under the slab.
Another approach to making the basement dry for interior finishing follows.
APPROACH 6:
Finishing a Basement with Moisture Problems
Using the interior drainage system shown above in Approach 5, one method of finishing the space is shown at right. A polyethylene vapor retarder is placed over the foundation wall before installing finishes.
"Or extend the membrane up the wall.(comment by JGC)". No interior vapor retarder should be placed over batt insulation when finishing walls if there is already a vapor retarder on the foundation walls. There should be an interior air barrier (such as the wall finish material) sealed at the top and bottom plates and at all penetrations. Rigid insulation is placed on the floor and then covered with a decay-resistant plywood sub-floor.
Attention:
Check your local building codes for this type of
installation.
APPROACH 7:
RECOMMENDED Our
choice for interior applications!
Complete Interior Drainage System with a Finished Interior
For basements with severe problems, it is possible to use the interior drainage system shown in Approach 6 and extend the dimpled plastic sheeting over the entire wall. The sheeting serves as a vapor retarder and it forms a drainage layer connected to the drain pipe below. This is particularly effective if the wall is to be finished. A second interior vapor retarder should be avoided, however, if batt insulation is used. There should be an interior air barrier (such as the wall finish material) sealed at the top and bottom plates and at all penetrations.
The dimpled plastic sheeting can also be placed over the floor and covered with rigid insulation and a tongue and groove plywood sub-floor. This forms a vapor retarder and drainage layer on the floor.
Problems with Finishing
If a basement has moisture entering through walls or floor, covering it with any kind of wall finishing material or carpet is likely to make it worse unless the water is dealt with first. Wet carpet and moisture under wall coverings are excellent places for mold and mildew growth that can lead to health problems. Generally, when the relative humidity (RH) is above 60 to 70 percent, problems occur with mold and mildew growth.
Mechanical Ventilation
Mechanical ventilation pipes connected to a suction fan can be fabricated to the dimpled sheeting. This draws moist air from beneath the sheeting and dries out the floor. It also assists in controlling radon and other soil gases.
Call Johnson Group Contracting today.
705-728-3476
