I am writing at the request and on behalf of my son. He is in the process of having a new house built and it is now at the stage where the painting is complete and the basement walls will be put up shortly. The contractor has indicated that the studs will be spaced at 24 inch on centre, rather than the normal 16 inch.
Will this 24 inch spacing require a thicker drywall to compensate for the lack of support? If so, what would be the minimum thickness?
Thank you for your time and anticipated prompt reply.
In regards to general house construction, there are only two ways to do things: The right way and every other way. That is not to say that the other way or ways will not work, but they are not the best possible option. Your situation falls into this category, and we will explore this further.
Most North American building materials for residential and many commercial applications are designed around original Standard measurements. These measurements are based on the units of 12 inches per foot. This is important for most building components such as dimensional lumber and sheet goods. The sheathing includes drywall, which is typically sold in 48 inch widths and various lengths, with 96 inch lengths being the most commonly used in basements. When things are based on multiples or fractions of the number 12, building design and components must also follow this framework for efficient use of materials. This is why it has been difficult to adopt the Metric system for measurements in construction.
For the above stated reason, typical house wall framing is installed at 16 inches on centre, which divides evenly into the 48 inch widths of typical sheet goods. This allows for quick and efficient installation of sheathing with minimal waste and cutting. This rather narrow spacing also ensures good support of wall and floor sheathing that is secured overtop. In many older homes, roughly 24 inches on centre was used for floor joist and wall stud spacing, primarily due to scarcity of building materials during various periods, such as Wartime. While providing barely adequate support, in many situations, this wider spacing can cause bowing in floor and wall sheathing. In some cases this may even cause overloading of floor joists and walls studs and severe warping or cracking.
Excess bowing or cracking should not be an issue in the basement walls in your son’s new home, which will have minimal loads applied, but may lead to bowing in the drywall or uneven walls. Slightly warped studs will be more noticeable and spacing for divider wall backing and electrical outlets and switch boxes will be somewhat more difficult to plan. If additional paneling or wainscoting is installed over the drywall, these imperfections may be more noticeable. Installing thicker drywall may be a partial solution, but does not make economic sense.
Gypsum board sheathing for walls is commonly 1/2 inch thick, with thicker 5/8 inch available that is normally used for fire separation walls. The thicker drywall is more costly and considerably heavier and more difficult to transport. This second quality should be taken into consideration when attempting to bring multiple sheets into a basement that may have poor access. Narrow stairways may have to be negotiated, and carrying extra heavy drywall will be troublesome.
As far as cost, the cost of the additional studs may not be much higher than that required for the more expensive 5/8 drywall. Spruce studs are currently at a very low cost, compared to the last few years, and changing from 24 to 16 inch on centre should only add minimal extra expense to the overall cost of construction. This is particularly important for shorter interior divider walls, which may be more difficult to frame with the larger spacing. The perimeter walls inside the foundation could be done with the larger spacing, but this may create another problem. The wider spacing may not prevent inward bulging of the friction-fit fibreglass insulation installed between the studs. This will make drywall installation more difficult, and may show seams and joints more readily, due to the bulging of the insulation.
The difference in cost for the additional studs may be only a few hundred dollars, or less, for a typical sized home. That is minimal in the overall scheme of things for new home construction and would be a wise investment. I suggest you have your son discuss this with the builder, and offer to pay the additional cost of the material to have the more appropriate stud spacing. It takes minimal extra time to frame a wall with 16 inch centres, rather than 24, and would be much more time consuming and difficult to add extra framing later on.
Homeowners and builders have often tried to save money on insulating and framing basements by using smaller studs like 2 by 3’s, wider spacing between studs, or lower grade lumber, but the final results often suffer. You are correct that the possibilities of bowing walls or drywall may have a detrimental result on the overall look and quality of the finished product.