We have an insulated concrete form (ICF) basement and are putting up drywall as per code. There are some areas that we can’t access to put up drywall, including behind the furnace. Is there anything else you can suggest that might work?
Thank you — Paulette
Answer: There may be a few different options for covering your foundation walls which may not employ conventional methods you are using in the rest of your basement. Thinking somewhat outside the box can often be a good method to solve a difficult situation like limited space to install wall coverings.
Insulated concrete forms or ICFs, are a relatively recent product that incorporates foam insulation in the process of pouring concrete. When assembled, the foam blocks act as the actual form, replacing traditional plywood or metal styles, to hold the concrete in place until set. The opposing sides of these units are held together with plastic bars or webs, eliminating the need for metal form ties. This saves significant time and labour in not requiring removal of the forms and removal or cutting of metal ties. The other benefit of this system is eliminating the need to insulate the foundation wall on the inside or outside.
Once the concrete is set, and the rest of the house is built over top of the ICF foundation wall, finishing the interior is relatively easy. The plastic components of the ICF units actually become anchors for fastening sheathing directly to the foundation. Because of the unique design, no polyethylene air/vapour barrier is required. So, installing wall sheathing is quite easy by screwing directly to the plastic anchor locations. While some jurisdictions may allow the ICF to remain uncovered in an unfinished basement, others may require the foam to be covered for safety enhancement.
The foam insulation in an ICF, and many types of rigid foam boards, may emit toxic compounds if burned. Because this material is present inside the living space, it should be covered with fire-resistant material to prevent easy combustion. Depending on the requirements of your municipality or city, and the type of building, this will normally range from a layer of Standard drywall to one or more layers of thicker fireguard drywall, which has a higher fire rating. The higher the rating, the longer it will take for an active fire to penetrate the gypsum board and ignite the foam insulation.
Enquiring what type of drywall is needed in your basement is important before proceeding. Once determined, the easy to reach areas of your foundation may be covered by simply fastening the sheets directly to the ICF fastening points with appropriate drywall screws. If the surface of the ICF or fastening points are uneven, strapping the surface beforehand may help prevent uneven drywall seams, which can make taping the wall more difficult. This will increase the room needed for application, which can make your dilemma even more difficult to address.
It may appear that you will have trouble securing the drywall sheets behind your furnace if there is not enough room to fit in, but other choices may be available to you. While use of a thinner or more flexible wall covering may seem like an option, it may not achieve the fire rating necessary for adequate protection. Since the drywall sheets required are less than one inch thick, you may only need a little more room than that to install the wall coverings. There are more ways than one to fasten the drywall and using some form of adhesive may address your issue.
Many types of construction adhesives are available that will bond just about any type of wall covering. These may be available in cans or tubs to apply to the back of the drywall with a trowel. Even more common are glues sold in caulking tubes, which can easily be beaded on to the back of the sheathing in a desired pattern for good coverage. Once applied, only a few extra centimeters may be needed to slide the sheet behind the offending furnace. The drywall may have to be temporarily secured to the wall until the adhesive sets, but wedging anything behind the furnace cabinet that firmly holds the drywall against the foundation should suffice. Make sure any shims or blocking can easily be removed without damaging the surface of the drywall or the furnace cabinet.
The final consideration is protection of the foam insulation on the ICF, itself. Fastening rigid wall sheathing to the inside plastic foam should only be attempted if it is not damaged during installation. Care must be taken not to take chunks out of the insulation during this operation, otherwise the insulation properties may be reduced. Also, many solvent-based adhesives can actually react with the foam, causing it to deteriorate or melt. Make sure you use an adhesive specially designed for use with rigid foam insulation to prevent irreversible damage.
Typical fastening of gypsum wallboard to your ICF foundation may be done with conventional drywall screws, but other methods may be possible to secure it in the other locations that may seem unapproachable. Employing construction adhesive designed for use with rigid foam insulation, instead of screws, may allow you to comply with fire safety regulations in covering the combustible foundation interior.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
