Last week, we published an article starting a conversation about several fundamental aspects of basement foundations and waterproofing. Not all houses in Washington, DC or even commercial buildings for that matter have basements. Some of those buildings are set on relatively shallow footings, generally built below the height of a frost line, but in some cases even shallower than what is required by modern code (to be above a frost line). In Capitol Hill, Georgetown and other historic neighborhoods of Washington DC though there are thousands of buildings built in rowhome type configurations with basements. Not all of these basement areas were originally finished and even today some of those areas remain unfinished, just used for the sake of utility purposes.
Today we’ll take a closer look at areaway drains, typically used on the exterior of buildings in areas that are significantly or even just slightly below grade. Areaway drains can also be installed in interior spaces. In some cases areaway drains are similar to shower drains.
The outline for today’s article follows:
- Where Areaway Drains are Needed
- Hydrostatic Pressure Relief Weep Holes
In a coming article, we will also follow up on areaway drains and touch on the following topics:
- How Areaway Drains Work
- Alternatives and Options
- Areaway Drain Upkeep and Maintenance
Where Areaway Drains are Needed
Basement entrances are often set below grade, the level of the ground surrounding a building. Area drains in below-grade contexts, such as external below-grade entryways or window wells, collect water runoff precipitation or as heavy rains may flow at the base of a building. Areaway drains prevent water infiltration into basements or lower levels of buildings by providing a drainage point for water that collects in these below-grade spaces.
Last week we talked about basement wells and we presented the photo below. This particular example is a bit of an anomaly. It’s very common for an entry well such as the landing at the bottom of the stairwell, below grade at the entrance to a basement, to have an areaway drain or a linear trench drain. It’s rare though for an entrance like this to have both a linear trench drain and an areaway drain. Normally it’s either one or the other. It’s important for the concrete base floor of the landing or bottom of the stairwell to be sloped towards the drain. In this case though since there are effectively two different drains it’s an odd context or configuration for the slope to go in both directions. It’s possible to build a crown between each of these drains but that’s not the case in this particular circumstance and it would be an odd unique configuration.
In the context of construction and architecture, a “well” can refer to various features designed to create access, allow natural light, or provide escape routes in below-grade or partially below-grade structures. Common types of wells include window wells, entry landing wells, and root cellars wells, common in historic masonry buildings of Washington, DC, for example.
A window well is an excavation or structure built around a below-grade window to allow natural light into basement or below-ground spaces. It often includes steps or a ladder for safe egress and may serve as an emergency exit. Codes, outside of the building code, in many circumstances require multiple means of egress. A below-grade stairwell well is an enclosure or shaft that provides access to a basement or lower-level area through stairs. It is typically designed to facilitate safe and convenient movement between different levels of a building.
These wells can vary in design, shape, and purpose but are generally constructed to enhance the functionality, safety, and aesthetics of below-grade spaces. Window wells, for example, are particularly important in basements to provide natural light, ventilation, and emergency egress. Stairwell wells are essential for safe access to lower levels, and coal cellar wells are used to create conditions for coal storage, in historic heating applications. Each type of well serves a specific function in the context of a building’s design and use.
Similar to a well, in some ways but different in overall context, the picture below shows an areaway drain in a paved patio area. Like a well, one side of the paved patio area is below the upper grade, but the other side of the paved area leads to steps going further downward. Instead of installing an areaway drain as shown in the picture below, the water could be directed down the steps. However, in climate such as here in Washington DC where there are numerous freeze-thaw cycles every winter, draining water down a set of masonry or brick steps can cause a slip hazard area where ice slicks can build up with flowing water in rains at temperatures hovering around 32°F.
When simply walking on the brick paved area, it basically feels natural in flat, but there is a very slight grade headed towards the drain. Graded areas like this should have a pitch of at least 1/4 inch of fall per linear foot and no more than about ½ of an inch per linear foot. 3/4 of an inch of grade per linear foot, for example, is relatively extreme. More than about 1/2 of an inch will make the area feel like a palpable or noticeable angle, slope In the range of about 1/4 to ⅜ of an inch per linear foot is a better range.
Hydrostatic Pressure Relief Weep Holes
The picture below shows the greater context of the area, entrance to the lower level from the exterior, the landing, the stairwell and the base of retaining walls at the below grade entrance stairwell at the side of the building. The masonry walls at the sides of the stairwell were built without proper or modern types of waterproofing and or hydrostatic pressure relief systems. You can see efflorescence on the surface of the brick including discoloration from prolonged exposure to groundwater without proper mitigation systems. Retrofitted weeps have been installed into the historic brick masonry walls of the retaining wall but those weeps or a secondary type of mitigation and are treating the symptoms instead of the disease. (In this particular case, we refer to this type of weep hole as “retrofitted” because it has been installed after the original construction of the wall and it is not a proper hydrostatic pressure relief system.) If the hydrostatic pressure relief system was installed or built at the time of construction of the retaining wall then it would be an overall more elaborate system with additional components. Some of the additional components include a horizontal or parallel perforated collection pipe that runs in line with the base of the wall and a filter fabric type sock or blanket that wraps around the pipe only separated by crushed stone or aggregate rock. Together, these elements allow the system to effectively drain water, and mitigate build up of water on the exterior or Earth side of the wall. Weeps allow a near-constant stream of water to run from the retaining wall and then land on the concrete area way and across the area away towards the drain. While this type of installation may be better than no weeps at all, this particular installation is still fraught with a list of shortcomings and problems. One of the key sources of these problems is that as water builds up against the wall, as the hydrostatic pressure increases, it leads to permeation of the water into the joints of the masonry retaining wall which accelerates deterioration. Restoration and remediation attempts such as repointing or tuckpointing or joint pointing are largely effective in most cases of restoration at facade walls, for example. However, in cases of hydrostatic pressure, repointing only addresses the common symptoms, not the root causes.
Water can enter from above, run down the steps or permeate and or drain through the retaining walls. This particular stairwell has an enclosure built above, yet, it’s not a permanent or fully weatherproof envelope. The old masonry walls of the surround lack proper hydrostatic relief. The drain has been applied after the original construction and is undersized. As well, more weeps should have been installed, one is insufficient, and they should be installed lower in the base of the wall. A full perimeter water collection system could have avoided dumping water directly at this location which leads to an icing / slip danger in the winter. Dumping a concentrated load of water directly at a walkway is a danger and a nuisance which could have been avoided through better initial design.
There are different levels of potential problems associated with drainage and areaway drains at paved areas, particularly at wells or suppressed locations like landings at stairwells. One of the main and primary concerns is preventing water from building up and reaching a weir or dam location like a door transition or threshold. Once water builds up to a point that is higher than the threshold, water will enter in around the door. Like we mentioned above, residential or even commercial or industrial doors may have strong properties of water tightness or waterproofing, but they are not as watertight as a submarine door. Water will get around the opening between the door jamb and the door leaf itself once water builds up to the height of the transition or threshold, so the primary concern is understandable: keep water flowing away so it doesn’t flood into the interior of the building.
A secondary but nonetheless important goal of these drain systems is to prevent water from deteriorating the concrete, cementitious-based, and or brick or masonry paving at the patio and adjacent retaining walls. Several different types of building materials are available for building things like dug out or excavated stairwells, window wells or other suppressed areas below grade. By and large though the number one type of material used for this type of construction, in Washington DC and surrounding areas, is brick and masonry. In some cases concrete or stone are also used but brick is one of the largest types of classifications of materials used in retaining wall construction in Washington DC. Protecting this masonry from accelerated deterioration is essential in preserving the health of the structural elements of the building. Brick pointing and or repointing are types of restoration that are typically done to improve the condition of brick masonry, particularly in the case of historic brick, but repointing or tuckpointing alone is not enough to fix the problems associated with drains in areaways or paving that do not work properly.
The collage of pictures below shows several different types of catch basins and or ground drains that are similar to areaway drains but instead of being installed in typical patios or areaways, they are installed in areas where ponding or flooding happens because of low grade, in comparison to the adjacent grade. They work very similarly.
Historic masonry upkeep and preservation
To properly maintain, repair, and care for these historic buildings, a knowledge, interest and understanding of historic building principles is required. Here in Washington DC, historic masonry buildings are extremely expensive and the amount of financial loss caused by improper repointing and low quality construction is staggering. However, in addition to the direct financial value of the property, there is also a cultural loss when historic buildings are damaged. By comparison, consider neighboring poor cities, when historic buildings are damaged, it’s not just the loss of value to the property owner, there’s also a loss to all inhabitants and visitors of a city, present and future, who care about architecture, history, and culture.
We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the historic built environment of Washington DC and neighborhoods such as Capitol Hill, Dupont Circle, and Georgetown and become educated on on the difference between proper historic preservation versus improper work which leads to significant damage to the historic fabric of a building.
From a conservation and preservation perspective, several approaches can be taken to improve conditions related to deteriorated historic brick masonry. Primarily, lime mortar brick joints and low temperature fired soft red clay bricks should be inspected and checked on a routine maintenance schedule, either seasonally or at least annually. If brick masonry is kept in good condition, the life of embedded wood elements can be significantly extended. Hire a professional contractor which specializes, understands and appreciates historic construction elements and buildings.
You can learn a lot more on our blog. Feel free to check it out. If you have questions about the historic masonry of your building in Washington DC, fill out the webform below and drop us a line. We will be in touch if we can help.