Roof top deck on not so flat rubber roof

Roof top deck on not so flat roof
I am installing a deck on top of a new rubber roof (over a first floor finished room) that measures approximately 26 by 14 feet. The entrance to the deck is from the second floor of the brick home in the middle of the 26’ run. The entrance threshold is just over 5†above the rubber roof (just enough room for a PT 2 x 4 on edge and 5/4 x 6†PT decking on top). The customer’s budget will only allow for PT which I may later stain.
One problem is that the new “flat†roof is not quite flat. Although the highest point on the roof is (thankfully) closest to the entrance from the house, the slope to the edge is not smooth and not much (maybe a one inch drop over the 12 to 14 foot width of the roof). Puddles abound and could be as deep as ¾â€ though most are probably ½â€. My first question is how to best construct the deck. All of the posts (6 feet or les apart) have been bolted or lagged to the ceiling joists of the room below and sealed where they penetrate the rubber roof.
One carpenter suggests attaching 2 x 4s PT sleepers, perpendicular to the side of the house (installing a ledger board to the brick wall first), as low as possible to the bottoms of the posts. Because the roof is not level, the resulting deck would be undulating (along with the roof). We’d place rubber strips between the sleepers and the rubber roof. We’d also likely have to “shim†the 2x4s in places where they make no contact with rubber roof for more than a couple of feet.
Another carpenter suggested making the deck in square sections (4’ x 4’?) what would simply be laid on top of rubber strips on the rubber roof. According to this 25-year veteran, this would enable roof repairs (if they were needed) to be made easily. I imagine that the deck sections would be difficult to construct so that their surfaces would all match given that they’d be lying on top of roof that’s not flat.
Another possibility is to gently slope the deck so that the highest point were level with the entrance threshold (next to the 2nd floor fo he house) and then sloped down 1†over the 14’ away from the house. Many of the 2 x 4s would likely have to be scribed and cut with a jig or circular saw in order to accomodate the irregular contours of the rubber roof. But this might produce the most level deck, at least of these three suggestions. It also would be time consuming to scribe and cut the sleepers.
Currently, I’m leaning slightly toward the third option but I’m open other suggestions.
Grateful Don
Second question: If I end up running sleepers perpendicular to the house, I’ll likely need to attach a ledger board along side the (brick) house. The current (copper) flashing is old (probably 50 or 60 years) and it extends probably 8 or so inches above the roof before disappearing between 2 courses of brick. If I end up attaching a ledger board to the house, could I simply attach the ledger board through the flashing into the brick?
Or, would it be better to cut the flashing approximately 4†down from the top and fold the top piece of copper over the 2 x 4 PT ledger board which would be attached (under the top piece of flashing) directly to the brick? This would effectively use the 2 x 4 ledger as part of the flashing system by directing water over the bottom piece of copper flashing (between the house and the ledger board). My concern is, could water seep up under (and in back of) the 2 x 4 and run down the back of the bottom piece of copper flashing into the room below. Once again, I’ll be grateful for suggestions.
Don
Replies
Hello Don. I would not attach it to the home at all and let the deck rest on blocks and strips of rubber. You wont have to assume responsibility for flashing and you wont trap moisture.
Making the deck in sections is a good idea for repairs. Most rubber roofs only last 10 years or so. If the deck is maintained well it could last much longer so having access would be beneficial. But with this benefit comes higher costs. Making it all in sections is time consuming. I would give the customer two prices. One for each design and give them your recommendation as to which is better. Let them make the choice.
I would also make an entrance way onto the deck from the door . A small section made from 2x4 framing. Lets say 6x6 or so. You could get cute and go half circle or a dog ear shape. I would then set 2x6 framing on top of the edge of this section and build the remainder at this height which is high enough to get over all the bumps and maintain my full 2x6. This would be cost saving and allows you to do a better job regardless of whether or not they want it done in sections.
If they don't go for it then I would stick with your option 3.
Oh yes! Thank's Piffin! Never did address the puddlings! No product will do well with roof puddlings. The best bet here would be to remove roof, fix pitch issues and install a "Polar " system which would act as a roof and deck. The cost would not be to bad when all is said and done in comparison.
Fine Home Building did an artilce on this a while back which included sections.
Edited 3/19/2007 4:10 pm ET by AllTrade
Good points except that a good well installed rubber roof can last forty years.One problem is that the term rubber is applied to many products. I normally think of EPDM, but this may be Modified bitumen torch down
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Your right , nine out of ten people call Modified Torch Down rubber.
OH MY, WE'VE GOPT A LOT TO DO HERE...
First things first -
There are a lot of threads with photos discussing this here. Search under key words EPDM, IPE, Roof and deck and sleepers. I have done a lot of those so you could add search for replies by me. I've done eight of these over about twelve years - more lately
I would consider it a waste of time and money to place a deck over this roof, because the roof itself does not meet standards and will very likely leak and then it will be blamed on the dck builder. The roof should have a slope of 1/4" to the foot and should not puddle water at all. 3/4" is excessive for any roof.
So that means that the individual removeable pallets is the only way to go here but if they can only afford PT and not IPE, then they cannot afford the extra labor it will take to build that amy extra partions, nor can they aford to reslope and reroof the roof itself.
But can they afford the cost of the leak when it ruins the house?
Of course they can - it will be on your insurance or the HO insurance...pardon my sarcasm for a minute.
No ledger to the house is necessary.
Check for the other threads and see what followup questions you might have. I hesitate to get too involved with this pone because IMO, it is doomed from the start. Sorry
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
you are only talking about 14 sleepers to scribe... 24" o/c or....
if it was me working with what you have to work with...
for my sleepers i'd use a 4" strips of torchdown on top of that i'd use pt 2x4 on the flat with a 2x4 on edge deck screwed to the center forming an upside down T on 24" centers... i'd then level them up and fill low spots under these with more strips of torchdown on the house side i'd leave them open on the down side i'd use use one 2x4 as a rim joist just to close it up and keep them in place as i screwed off the decking... i would screw it off (the good $65 a bucket green deck screws) just in case you needed to pull up a few for a repair...
the only option i might go for is use'n a 2x6 for the flat on the roof part to spread the load a little more... other than that i really don't see an issue with it... should be fine
you might have to rip 1/4" to 1/2" on some of the 2x4's on edge to get it to level out ....
should be a 1 day job
p
Same problem as I am working on now.
Roof top deck above living space. Originally built with tile on deck, sloped the wrong way (I was told).
Leaked, so tiles tossed, torch-on roof installed and wood platform deck over re-sloped deck surface - but with drains in deck still installed. Wrong drains (made for vinyl roof) so they leaked.
I've just had the torch on re-done (granular), but with the extra layers for the drip-edge and all, I have a lake in the centre. So what I did was got a load of 1/2" styrofoam insulation and PL 300 and I'm going to glue on the foam board to displace the water. I'll space and shim the existing deck sections upon re-placement with my left over AZEK and left-over membrane under that.
Should be Kool!
Quality repairs for your home.
AaronR Construction
Vancouver, Canada
Thanks for your suggestions.
I think my customer will like Aaron's suggestion best (he'll get a deck out of it) and therefore so will I (as long as the "styrafoam" does its job of displacing the water). If anyone has long-term experience with this, e.g. what's the lifespan of the "styrafoam," I'd like to hear from you.
Thank you all for your help.
AHA!
I called the Styrofoam people this AM>
"It should work OK, since styrofoam has been used as a flotation device for years."
???PL300 Foam board glue? "That will be great, and, if you need to melt 2 pieces together to form a larger section, or add on, some of that low-expanding foam used for insulation works wonderfully as a glue".
You sure?
Absolutely, he said.
Good luck.Quality repairs for your home.
AaronR ConstructionVancouver, Canada
I just returned from being out of the country and called a regional building supply house to ask for a "rubber" (EPDM) cement and styrofoam. When I described my situation, he recommended a product made by Henry's (I think) that it is called something like, puddle fill. It comes in a large can for around $50 US and is mixed with water to fill in depressions on rubber roofs (enough to cover about 12' sq feet at 3/4" deep). After curing for 2 days, a fabric is adhered on top with a different adhesive. Hopefully this is in time for Aaron's project. My customer is postponing his deck ($$) and his roofer (I'm so glad the roofer was my customer's roofer and not mine) hasn't returned calls about the puddling on the brand new EPDM roof.
THanks again to all for your help.Don
I just got your post. Sorry, busy.
Here is how I solved the problem.
I deep-sixed the idea of the styrofoam - glue incompatibilities.
I ended going to a roofing supply store, and got 4'x5' protection board.
Filled in the deepest depressions as best I could, and used the little left-over pieces as shims.
It works.Quality repairs for your home.
AaronR ConstructionVancouver, Canada
Excellent.
Good to know yet another option if I come across this problem in the future though I'll be more careful to specify no depressions in flat roofs.
Don