Dry Below Decks Made Easy – Part 2: Below vs. Above

When a 2nd level deck needs to serve as a roof for a lower level deck or patio below, you can save time and money by using a SINGLE product that is approved as BOTH a traffic coating and roofing membrane in one. If you have an upper level deck surfaced with Duradek vinyl membranes, you don’t need the expense of an under deck drainage system to keep the area below it dry.

Whether for investment properties or your own residence, getting the most from your outdoor living space includes maximizing the usable space. By turning an upper level deck into a roof for a lower level deck below you gain the advantage of dry outdoor storage or a place to enjoy the outdoors even when the weather conditions are less than perfect.

Using a Duradek vinyl deck membrane is the ideal solution as it provides an attractive pedestrian deck surface while simultaneously acting as an approved roofing membrane with all of the waterproofing details that need to be considered with roof-grade waterproofing. Under deck systems only serve as a water routing system (and sometimes a ceiling for the lower level deck) but your exposed walking surface of the upper level deck would have to be addressed separately.

When you need it to stay dry below an upper level deck. a
walkable roofing membrane like Duradek is the best option.
View Case History #157 on YouTube

A Look at Under Deck Drainage Systems and Why They Might Not be the Best Water Management Solution

There are two basic types of under deck drainage systems; both of which function by allowing water to get through the upper level deck surface and route it between the joists to downspouts and gutters. Theoretically, both of these systems have advantages but realistically neither of these systems provides complete water-tight protection for the building envelope. Water is routed away from the structure, but moisture is still present and trapped with little to no air flow. In addition, since the water routing systems are enclosed, you are unable to visually inspect if all seams or seals remain intact, and only discover those points of vulnerability AFTER there is a leak.

Last week we took a closer look a Trough Systems, which manage the water by routing it between the joists and is completely enclosed by upper deck above and soffit system below. This week we will take a closer look at Panel Systems which routes water below the joists and also often serves as the finished ceiling for the lower deck.

A Closer Look at Dry Below Deck Panel Systems

While a dry below panel system acts as the water routing system and ceiling for a lower level deck simultaneously, it also has its own set of challenges. Advantage - It can be used on an existing deck. Disadvantage - It is labour intensive as it relies on a sloped sleeper system to provide the slope needed to route the water. An elaborate spacer system is attached to the underside of the joists to provide a pitch of ½ inch every 4 feet.

Installation of the actual system begins with attaching a wall trim around the perimeter to create a frame. This includes drilling into the outside of the house and any penetration is a point of vulnerability to be caulked and checked periodically to protect the building envelope.

Installation of a below deck panel system.

All of the other pieces of the system just snap into the frame. In most cases a supporting beam(s) would be used to provide strength for the system. Basic panels serve as the decorative surface and are installed side by side to enclose the joists above. The panels are often PVC and they are flexible enough to install in the frame, but rigid enough to crack or snap when cutting to the appropriate size. The panels snap into the frame system and provide multiple non-permanent seals as they snap into each other to enclose the ceiling.

A gutter is installed on the outside perimeter to catch the water from the slope provided by the panels on the spacers. Water wicking or splash back can occur here so careful installation of the gutter is very important.

Like the trough system, panel systems still require the upper deck surface to be treated or installed separately.

Why Duradek is the Best Choice to Keep it Dry Below

Duradek vinyl deck membranes have been waterproofing decks for over 40 years. Duradek is CAN/CGSB, CCMC and ICC approved as a pedestrian traffic coating and a roofing membrane. It includes warrantied waterproof protection for 10 years, while its traditional service life reportedly averages 20+ years. Unlike many other vinyl deck products, Duradek also offers a written appearance warranty.

Duradek vinyl deck membranes are installed in a single application with methods that consider the details required for secure waterproof protection of the building envelope. Since those critical waterproofing details are so important in protecting the home, Duradek is installed by authorized contractors that have been specifically trained in Duradek’s installation methods.

How Duradek Vinyl Deck Membranes Work

Duradek is adhered directly to the deck surface. The ideal substrate is ¾” T&G Untreated Plywood, however Duradek can also be applied to concrete surfaces. All seams are heat-welded to ensure no water can ever penetrate. The membrane is run up the inside perimeter of the deck against the exterior of the building before the flashing details are added. Particular attention is paid to any areas of vulnerability like door openings.

Water is managed by a 1” in 12” surface slope to the outside edge. Depending on the type of deck, waterproofing details such as edge flashing, drains, scuppers and a gutter system is included if required. All of these waterproofing details are heat-welded or caulked to be completely sealed. The seals are accessible for annual visual inspections. There is less of a chance of surprising leaks with Duradek.

Duradek 'Cork Natural' vinyl is a low maintenance deck surface
as well as a roofing membrane to keep it dry below.

Get the Upper Hand on Your Upper Level Deck

There are several advantages with designing your second level deck to provide cover in order to create dry, usable space below. Sometimes you need dry outdoor storage space for bikes, lawnmowers, sporting equipment or other seasonal items. Maybe you like to spend time outdoors all year round and that protected area provides shelter from the rainy days, or alternately in peak summer season you can get a little shade when you just have to get out of the sun for a while.

Whatever motivates you for creating a dry area below your upper level deck, choosing Duradek and one of its 24 attractive colour options is the best choice for low maintenance decking that doubles your usable outdoor living space.

Duradek vinyl deck membranes provide roof-grade waterproof
protection for a lower patio and dry storage for outdoor items.

You can contact an authorized Duradek Installer in your area for a free estimate on your next decking project or to answer any questions you might have on deck waterproofing.

Check out last week’s article where we compare Duradek to the Trough style of under-deck drainage systems in “Dry Below Decks Made Easy – part 1”.