A Roof-Top Deck


New Hampshire Design and Construction

Low-slope roofs, often referred to by the misnomer “flat roof”, can sometimes be the perfect place to add outdoor living space.

In this case, our client’s home had been prepared to receive a deck a couple years prior. The master bedroom already had a sliding door out to the roof of the garage. The roof material was EPDM (black rubber sheets), and had decent slope (good drainage, almost no ponding water). The lighting and electrical outlets were also already in place. All we needed to do was select materials and build a deck! Or so we thought…

Actually this project went very smoothly, but you may have heard of the materials shortages. The north east was particularly hard hit with shortages of pressure treated framing lumber. This was partially due to interruptions in the manufacturing and distribution but, from what we understand, there was an increase in demand that largely drove the shortages. At the time of ordering materials for this build we had just completed two other builds which were affected by shortages. Then the suppliers started telling us they do not have pressure treated lumber and they do not know when they’ll get more pressure treated lumber. We needed solutions!

Shou sugi ban framing with rubber spacer

There is an ancient (not so ancient) Japanese technique known as “Shou Sugi Ban!” (emphasis added). We’ve used it a few times. Shou sugi ban is a method for treating lumber that leaves it more fire and rot resistant while also changing the appearance of the wood. The words literally mean “burnt cedar”, but the process can be applied to a variety of woods. We treated all the lumber with the shou sugi ban method and then sealed end grain and cuts. The treated lumber looked beautiful but in the long run would take too much time to be practical for our company.*

As we framed the deck we applied rubber spacers between the joists and the roof, every two feet. These spacers are ensuring the deck does not interfere with the roof’s drainage, they will ensure the deck does not damage the roof should there be movement over time, and the spacers allow for air flow which ensures the wood always dries out (the most important step towards preventing rot). The framing was then attached to the building using long screws, 1/2″ plastic washers/spacers and a liquid rubber flashing.

The decking and railing materials are Trex products**, which aren’t our favorite to work with but its difficult to argue this deck doesn’t look beautiful in the end. We also used a new fastener that we really liked. The deck boards were a near perfect color match to the house and the white railing system complimented the trim of the home.


*Thankfully our next few projects didn’t require treated lumber and at the time of writing the shortages are getting better.

**We took care to capture and clean most of the composite and vinyl “sawdust”.

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