Question: Recently, you wrote an article about the best materials to place on the interior walls of a cottage that is not winterized. I am in the process of renovating an old trailer into a cottage, from the frame up. Exterior walls, floor, and ceilings are all 2x6 construction, to be insulated and vapour-barriered. Exterior walls are vinyl siding, and these are asphalt shingles on the roof. I would like to put a knotty pine board, or something similar, on the ceiling and have been leaning toward drywall on all interior walls. As I have misplaced the article, my question is, would these materials be sufficient to withstand the winter months without heat?
I look forward to your response and would welcome your advice.
— Glenn Hodgson, Birtle
Answer: Choosing wall-covering materials for a cottage or home that will not be used year-round may be more complicated than for a typical home, but should not be overly difficult to decide upon. Pick a product that looks good, requires minimal maintenance, and will withstand extreme temperature fluctuations — that will be the best decision.
There are several factors that you have to take into consideration when picking wall and ceiling coverings for your seasonal trailer conversion project. The first consideration should be durability in the harsh changing weather conditions. Drywall, while quite resilient in most situations, may not be the best product for the inside walls of a building with the heat shut off for large portions of the year. While the drywall sheets themselves may resist fluctuations well, winter cold temperatures can cause drywall compound to shrink and crack. This can leave unsightly cracks or lifting drywall tape. Also, condensation may be an issue in your enclosed trailer space and moisture on the surface of the drywall can cause staining or further deterioration to the tape. This may be most noticeable if condensation is heavy enough to drip down the face of the walls, pooling at the bottom. This can cause moisture damage and mould growth in the drywall itself, or baseboards on the floor.
Drywall, a gypsum-based wall covering, is a cost-effective product to produce a nice clean, smooth-looking surface. It is easily cut, installed, and painted and is the most popular wall covering for the majority of homes. Unfortunately, the composition of this wallboard makes it particularly susceptible to moisture damage if it gets wet. The gypsum is not very moisture-resistant and is exposed at the ends of each individual sheet. This material is covered with paper, which also has little protection from water damage.
To combat this issue, if you do decide to use it on your walls, ensure the surface is well-primed and painted with high-quality paints to prevent damage. Leaving a minimum 10-millimetre gap at the bottom of the sheets, above the subfloor, should also help prevent the wicking up of moisture that may collect at the bottom of the wall from excessive condensation.
Of further consideration for the use of drywall inside your seasonal home are the fasteners used to secure this sheathing. Common drywall screws are the most popular for this function, but these may not be the best idea for your purposes. These are painted or coated, but still have a tendency to corrode in a damp environment. This may be a further issue in your unheated building, as the temperature fluctuations can cause these fasteners to sweat and rust over time. They may also be susceptible to higher levels of expansion and contraction, causing drywall compound to pop off the surface, or loosening drywall sheets over time. Because of your seasonal use, choosing galvanized deck or flooring screws that are corrosion resistant may be a better idea if you choose this wall covering material.
As stated in the previous article you mentioned, wood panelling may be a much more suitable product for wall and ceiling coverings in a building that has the heat off for the winter months. Softwoods are resistant to excessive expansion and contraction, and allow moisture to easily flow in and out because of their composition. Cedar would be the ideal choice, because of its natural rot resistance, but may be too dark for a ceiling in a small enclosed structure such as your trailer. Pine may be the second-best choice, and a much more economically viable option. The lighter colour will be more pleasing than the darker cedar and consideration should be given to using it for the wall coverings, as well. The only concern with pine panelling is that it should either be kiln-dried or properly air-dried before installation. I have seen significant shrinkage in tongue-and-groove pine panelling, which may require removal and reapplication after some time if the material is not properly seasoned. Sealing it with Danish or Swedish oil, or equivalent products, also will help prevent this excessive shrinkage.
Drywall is the most popular wall covering in our homes because of its low cost, ease of application, and durability, but may not be the best option for a building that is not heated in our harsh winter months. Choosing other materials, such as natural cedar or pine panelling, should ensure you don’t have major problems with excessive cracking, moisture damage, or mould growth due to extreme temperature fluctuations within your newly renovated cottage.
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.