Expert: Bruce E. Johnson - 11/11/2009

Question
QUESTION: Hello, we have a huge problem with a 1000 square foot flat roof which is supposed to be a deck.  It was never finished as such and is covered only with rolled roofing material.  Here is the problem:  Pine needles, oak leaves, palm tree seeds fall constantly on the surface, therefore whatever material we use to finish the deck with must not have holes, grooves, etc. in order that it can be easily cleaned.  Also, the surface is not entirely flat--there are low areas with standing water after rain, and yes, we now have a few leaks in those areas.  What I'd really like to know is what product(s)--outdoor flooring (other than tile or wood) would you recommend to finish the deck with.

ANSWER: Hi Jeanie, no wood or tile?  That kind of narrows your choices down.  I like to use composite decking in these situations, built in panels that can be lifted to clean under and that float or just sit on the roof.  It sounds like you are afraid of debris building up inside the cracks between decking boards.  A leaf blower or a stiff bristle broom will remove enough of the detritis so that removal of the panels for extra cleaning is something that is done every six months or so.  As far as other roofing surfaces..there are some rubber coatings mixed with ground up tires out there..If your roof structure is strong enough you can maybe pour a lightweight concrete slab on top..Or you can just level up the low spots and install a new heavy layer of rolled roofing material.  Whatever your ultimate choice be sure to install a railing, 42" tall with pickets 4" apart.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: Thank you so much for this information.  Regarding the leveling of low spots, is there a relatively light product that can be poured to level these low areas?  For instance one area is 100 square feet and perhaps 1 1/2 inches too low.  

Answer
Hi again Jeanie, there are several cementious type of underlayments that are mainly used to level floors prior to tile being installed that may work, however, unless you roof over the patch it will just eventually lift and float when water gets under it.  For a dip of 1 1/2" I would suggest, first of all, finding out why that depression exists and then attempt to fix it.  It may mean cutting out a section of roof, repairing the problem and then reroofing that area.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com