Wood sheathing wonders – Exploring IDS-DMV’s historical techniques
In historic times, buildings were sheathed with natural wood on top of wood frames, as opposed to the plywood and OSB sheathing common today. In historic brick buildings, this applies to the floor framing joists and the roof frame rafters. These areas were covered with a 1x material laid diagonally over top of the framing members to add rigidity, decking, end resist shear racking.
A photograph with 1X for subfloor sheathing floor sheathing laid diagonal to the floor joist follows below for reference.
The 1x material stands for 1″ by a particular other increment. Normally dimensional lumber like this is available in 2″ intriguements so you can easily get 1×2″, 1×4″, 1×6″, etc. The boards most commonly used for sheathing are they are generally 1×6 inches.
In another photo below you can see a more upclose view of the wood subfloor. At this location, diagonally laid wood subflooring measured with laser level to check variation, to be partially reused with new flooring installation. To address levelness, low spots were filled with additional built-up plywood and overall plywood was laid and laminated with a polyurethane subflooring designated adhesive.
A photo, below, shows areas of damage in the subflooring. In wet areas such as bathrooms and kitchens, we would normally expect to see a higher amount of damaged sub flooring. Particularly around toilets, damaged areas subfloors are common, we expect to see rot at wet locations. Toilet closet flanges have a tendency to leak over time and sometimes those leaks can go unnoticed for a significant amount of time before they are treated. That time between the start of a small passive drip leak (A drip at a toilet closet flange could be considered passive because it only occurs in a very limited amount and only coincident with the use of a toilet when flushing) and repair can lead to significant rot in a sub floor area. The same circumstances apply to kitchen drains. Kitchen drain pipe traps and areas of drain pipe branch connections at the wall riser / vents for kitchen sinks or kitchen sinks and other areas with sink drains and traps. As well where there are entryways to the exterior, door thresholds and door openings in general, especially after about 100+ years, these locations can have a significant amount of deterioration to the subfloor from leakage at door openings and thresholds. Another common area of subfloor deterioration is near through-wall or window AC units. This air conditioning equipments creates a liquid condensate as part of the thermal exchange function of the air conditioning and HVAC process. It’s common to find leakage from condensation drains that has infiltrated walls and led to deterioration of flooring and subflooring.
Historic wood, in most cases, is stronger than modern harvested wood of today. Old growth lumber had a tighter green structure and and was generally stronger. However, after a 100+ years, wood floor can experience moisture from the crawl space, in the case to the photo below. Also also in other cases what floor can become brittle through dry-rotting and just the dileterious effects of age. In the case of the subfloor in the image above, particularly at board ends, there are cases of splitting, checking, and cracking. The historic salvaged subflooring of this type needs to be observed carefully to determine its suitability and fitness for reuse.
The picture below shows an example of 1x wood boards used as roof sheathing underneath the former roof membrane. In the picture you can see that the roof membrane has been removed which allows us to get a look at the historic roof sheathing. Roof sheathing is very similar to floor sheathing except in the case of a roof it’s not intended for a floor finish or for actual floor space, and roof should be installed with some slope at all locations.
