If you are looking for a waterproof deck membrane, consider installing TPO roofing material on your deck.

While having a roof deck is a great way to increase living/entertaining space, one of the biggest issues that many homeowners experience is frequent leaks.

Properly waterproofing a roof deck is often a challenge, because the materials used most frequently, either EPDM rubber, or a Tar/built-up material, do not offer solid protection against leaks.

However, there is a much better, longer lasting alternative for deck waterproofing: a TPO roofing membrane. Its designed with hot air-welded seams, which makes it impervious to water infiltration.

While a TPO membrane costs more than rubber, you get the benefit of enjoying a leak-free roof deck for years to come.

Also, since roof decks are typically small (under 300 sq. ft.) the real difference in price is miniscule and can be as little as $200-400.

Therefore it is always preferable to use TPO (or PVC) membrane instead of rubber.

Learn more about TPO membrane costs, as well as pros and costs of installing it on your deck.

How Much Does A TPO Roofing Membrane Cost?

Being a highly durable and long lasting material, TPO comes with a higher price tag than EPDM rubber or built-up roofing.

Expect to spend about $6.50-8.00/sq.ft installed, on a normal roof. On roof decks you will spend about $9-11/sq. ft. installed. 

The cost will vary depending on the thickness of the membrane you select (we recommend using an 80 mil membrane, which will cost more), your location and the contractor you hire.

When estimating your total budget, you should also factor in the cost of

PROs and CONs of using a TPO membrane to Waterproof a Roof Deck

As with any material, a TPO membrane has a distinct set of pros & cons, that may not make it the right choice for every home.

Consider the following:

PROs:

1. Hot-welded seam technology makes the membrane impervious to leaks (when done properly). Also makes any repairs very fast and easy.

2. UV and chemical resistant surface

3. Durability and Longevity: TPO will not fail and start to leak after 6-8 years, which is the expected service life of EPDM and built-up materials waterproofing materials for decks.

4. Resistant to Damage: in case the deck will need to be removed in order to make some repairs/changes to the roofing membrane, TPO will not be damaged in this process.

5. Membrane can be installed over plywood or a concrete surface.

CONs:

1. High Price: TPO costs almost 30% more than EPDM or built-up roofing. This presents a major deterrent to homeowners with tight budget.

Installation Tips

To ensure that your roof deck is completely watertight and will last a long time, we recommend the following TPO membrane installation guidelines:

1. You should ONLY use an 80 mil membrane, because thinner membranes have a high risk of tearing.

2. It is important to use ONLY high density insulation or DensDeck under the membrane. Don’t use soft foam.

3. It is best to fully adhere BOTH the insulation and the TPO membrane. However, we’ve installed roof decks, where membrane and insulation was mechanically attached.

4. Install all railing posts outside the roof perimeter, to prevent unnecessary penetrations and possible leaks. This is important because railings and walls are a common source of leaks on roof decks.

5. When overlapping seams, we recommend using double welding on all seams to prevent and eliminate all possible roof leaks due to seam failure. Its much easier to spend a little more time to do a good weld, than TO take off the whole deck just to find one leak.

6. Leaks can be avoided by carefully flashing and caulking ALL penetrations.

7. If there is a door that opens out on to the roof deck, it must be flashed properly at the threshold. Avoid using sealants, as these will quickly fail.

Why it’s Important to Waterproof Your Roof Deck

Sound Waterproofing is the Number 1 Rule of quality roof deck design. Using quality materials, such as a TPO membrane and qualified contractor labor is key to making sure that the job will be done right.

Here is a list of common problems that homeowners experience when they don’t properly waterproof their decks:

1. Leaks: these usually occur in the waterproofing material, NOT the deck itself. Ponding water, which is often found on roof decks, also has nowhere to go but inside your house. A low quality membrane, such as EPDM rubber will allow water to infiltrate.

2. Structural damage: over years, water slowly enters the homes, rotting the framing, beams and studs. The worst part about this damage that it can go unnoticed for many years, and as a result will be very expensive to fix, once discovered.

3. Interior Damage: If your roof deck leak, you not only need to patch the roof, but also repair inside damages, which can cost $300-1000, depending on leak severity.

4. Mold: It’s not only very expensive to remove, but can cause serious health issues for people in your household, especially to those who already have respiratory conditions.

Taking care of these issues, is not only time-consuming and stressful, but also very expensive, and can cost a few thousand dollars in repairs.

It makes a lot more sense to spend a little more money on a high quality TPO membrane and a licensed experienced roofer, than fix unexpected problems later on.