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I’ve got a 60′ x 10′ second story deck I’ll be building later this summer. The deck will be open below. Mrs. Customer wants soffits and recessed can lights installed on the underside of the deck. My question….. can I use Water & Ice (Same as used on eaves of roofs) membrane as a waterproofer? My plan was to install pressure treated plywood over the joists, roll on the Water & Ice membrane and then attach the decking. It sounds like the easiest way to go about it. I’ve also thought about ripping the joists in half, attaching the plywood, then the Water & Ice membrane, then the other half of the joist, then the decking. Does this sound like alot of work that isn’t needed? Whats the best way to go about this from those with past experience? (I did search the archives but couldn’t locate any info)
Thanks,
Dave
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Dave, We just finished four decks. We are using a product called Grailcoat.. It is a portland cement product. It can be applied directly to the plywood. It creates a tough waterproof membrane. It doubles as the finished surface. I will try to post a picture. (having trouble with our digital camera)
* We are midway with a deck over living area that will cover with ipe', and this raises a problem with fastening the decking to the coated floor below. The integrity of the membrane you lay will be compromised by any fasteners that penetrate. We went;ripped joist for slope, to give a flat lid below. ACX ply glued and screwed. Elastomeric coating. ripped treated sleepers that lay in a bed of elastomeric caulk (Sikaflex or sim.) We are not fastening this sleeper down directly. Decking material screwed through the sleeper, through the ply, and into the joist below. Sort of agonized over this decision, as there have been many lawsuits over water damage here recently. Would recommend you consult with a decking waterproof specialist. He gurantees your coating, and advises on your finish decking fastening. You may even be able to build a deck that is fully floating over the coated deck, provided you have enough room below to drop the deck enough to allow for a sleeper that is thick enough at its thinnest part to take all the finish decking screw. We would have done this, but we were left with only 4" step out of dining room onto the finish deck. Ripping your joist in half, and building them back up sounds compromising on deflection, squeaky, and hardware/fastener intensive. We discussed elastomeric over the sleepers that the decking fastens to as well, and could not get a guarantee. The treated ply will be full of places that the adhesive on the ice and water will not make contact with. Some things to think about: expansion and contraction and friction wear of the decking on the surface below ( do you really want the decking grinding directly against the coating?) We are still looking for the perfect system as well for this application of decking over a coated surface below , keep us posted please on what you decide to do.
*Does anyone have any feedback or thoughts on a product called EPDM or EDPM for this same waterproofing application?
*Here is a picture of the deck. It is Grailcoat hand troweled directly to plywood. The deck is not completed. We will apply a texture with Grailcoat from a hopper gun.
*Please let me try again.
*Dave:We've had good results on 2 recent jobs with a self-sealing roll membrane similar to the Grace Watershield. It comes in 3'x60' rolls and is a peel&stick product. We start at the house and lap it up 6-8" on the walls and stretch it tight across 3 joists with the excess width hanging over. As we go to he outside, we let it sag in the middle until the edges just cover the top of the joists at the outside end. Cut it back about 4-6" at the rim board and you have a trough with a gradual slope to carry water away from the house. If desired, you can install a 6" gutter under the deck to carry away the runoff.My roofing supplier specifically cautioned against EPDM for this appl. since it is not self-sealing and you have the possibility of leaks around nail penetrations. Also, this product is much less expensive than EPDM and you don't have to glue the joints.Cautions:Since the material is designed for use under shingles, it has no added UV resistance. My supplier felt that installing under deck boards would provide enough cover, but you are still technically violating the warranty. I passed this along to my customers with the caveat that I could not warrant the application, but neither wanted to bear the expense of the Dri-B-Lo or similar system. I get this stuff for about $.33/sf.It comes in two surface textures, rough and smooth. You definitely want the smooth to avoid trapping grit.If you want to go more than 12-14', you can only get 16" of coverage to maintain some slope.You will need to prevent other subs from cutting on the deck after install, or your drainage paths will be full of sawdust. It is very difficult to clean after deck boards are installed. Just had a thought: maybe leave off the first run of decking against the house until everyone's finished so can hose down..First deck was appr. 2000 sf with no ceiling below and second was over a beaded ply ceiling of about 300 sf. Neither have shown any tendency to leak, although both have been in less than 1 yr.Will reserve judgement for several years and still have my doubts, but we have to give the customer what they want,eh?Can't for the life of me remember the name of the stuff right now but if you're interested, let me know and I'll look it up.Another solution if you have the height: drop the ceiling below and build a low pitched tin roof system in the cavity.