Walkable Roofdeck - Bulletproof Solution?


#1

Hi All,

We’re designing a walkable roofdeck with planters for our client. The walkable part of the deck will be redwood on top of the waterproofing membrane (i.e the roof itself won’t be walked on.)

We had originally detailed a PVC or EPDM heat-welded system over the plywood substrate, with extra thick strips under the duckboards and sleepers. Our contractor is concerned about this system for two reasons: 1) they worry about degradation from the elements, such as UV, water and freeze-thaw and 2)they worry about something punching a hole in it, and introducing a leak.

Is this the best system? Is there a more durable way to make a roof deck? Our contractor suggested a welded steel pan, or a poured lightweight concrete surface, but these seem overkill to me.

Thanks.


#2

We had originally detailed a PVC or EPDM heat-welded system over the plywood substrate, with extra thick strips under the duckboards and sleepers.

That’s actually what I would do except I prefer a 3 layer torch applied modified bitumen. Again putting extra non-torched pieces of material under any sleepers as cushion. I just feel it’s a more durable system than the two you listed. There are people more adept at flat roofing here than I though, maybe they have better ideas.


#3

If door height, and railing issues aren’t restrictive,
I would consider beefing up the framing. adding curbings
to complement the roof system, no matter what product you use, and construct the deck on the curbings.
personally, I would like a 4 ply pitch BUR with
Douglas Fir curbings/ all 20 oz copper flashings, and gravel top coat…
but of course…I am a dinosaur


#4

If it truly is going to get foot traffic, I would look into the concrete system; @ the least, get prices on it to determine if this is feasible.

Otherwise, go into a 3 ply system. I’m a peel & stick guy with no desire to do torch unless it’s a repair to an existing torch.


#5

In the situation you are describing I normally use .60 mil EPDM over 1/2" wood fiber.
Granulated torchdown is a great option also.


#6

[quote=“matthewmat1”]Hi All,

We’re designing a walkable roofdeck with planters for our client. The walkable part of the deck will be redwood on top of the waterproofing membrane (i.e the roof itself won’t be walked on.)

We had originally detailed a PVC or EPDM heat-welded system over the plywood substrate, with extra thick strips under the duckboards and sleepers. Our contractor is concerned about this system for two reasons: 1) they worry about degradation from the elements, such as UV, water and freeze-thaw and 2)they worry about something punching a hole in it, and introducing a leak.

Is this the best system? Is there a more durable way to make a roof deck? Our contractor suggested a welded steel pan, or a poured lightweight concrete surface, but these seem overkill to me.

Thanks.[/quote]

I was thinking lightweight concrete while reading your post before you mentioned lightweight. If you really want a bulletproof roof system, put down a durable roof membrane and pour a lightweight wearing slab overtop the roof. Before you pour the wearing slab, make sure you have the roof water-tested if feasible.

Other options would be something like a 3-ply BUR with an APP modified bitumen cap sheet, and install the deck in sections that can be removed. This would prevent repair issues like the wearing slab, IF and when the roof leaks.

I also recommend you utilize roof board insulation over the plywood, to help protect the roof from fastener back-out.

What are the dimensions, and what is it over?


#7

Hi Mat
Be happy to help… First may we start with your answers to the following 5 items :

1.What is the Size/Layout configuration of this new roof (Is the new redwood decking going to cover the roof area in it’s entirety)…please describe?

2.Is this a new building or new roof level you are design/building with a plywood decking over wood roof joisting or are you removing an existing roofing system down to an existing plywood decking or are you recovering an existing roof with new plywood to act as a substrate for your new roofing system…please describe?

3.Does or will this new or existing roof have definitive slope (if so what is it and is it one way/4 way etc…???)?

4.Does or will this roof have internal drains (size & how many)or is water run-off being directed to thru-wall or overflow type perimeter scuppers (describe which type)?

5.Are there many existing, new or planned future roof penetrations (describe type/size and number)other than those that you will most definitively need to lift,level and support your new raised redwood decking(we will discuss these new needed raised redwood decking posts/supports/columns etc. and there attachments/flashings subsequent to your reply posting)?

  • …So that we can further discuss your actual as is scenario(choice/type and application of new roofing and redwood decking including the configuration/placement/drainage of the planters proper, the possible need for additional R value insulation etc.etc.),I am anxiously awaiting your follow-up posting re: above needed info items …*

          GENERAL FYI
    

Most all roofing systems whether they be Modified/EPDM/Built-up/P.V.C/Hot or Cold Liquid/ Hypalon etc…(whether Conventional type or in PRMA configuration)are good and acceptable for this application .…to choose the most appropriate one, your budget, project access and number/type of penetrations and ability/configuration of structure to support new load weight will be the primary determinants.

…Re: UV
This should Not be an issue being that new decking will protect project’s new conventional type roofing membrane surface from degradation due to direct exposure (note: naturally, PRMA type systems are not affected by UV)

…Re: Freeze/Thaw
Possibly an issue for the redwood structure proper…However, this is NOT an issue for the new membrane roofing system….This is Not an issue since new proper supports/columns/posts etc. for this new raised redwood decking structure that are and will be required will be directly set atop/securely affixed and appropriately pitch pocketed/flashed to the building/decking proper and this new raised redwood decking will be set-up atop these supports/columns
…Once again, we can specifically discuss this and the many other detailed scope items of work based on your choice/type of new roofing system, type/composition and configuration of support/columns/posts needed and required for new raised redwood decking and your follow-up answers to above requested 5 items of general needed info…


#8

I can’t give you any answers unless you post what you ate for dinner last night and your girlfriends bra size…


#9

Dinner last night: pasta and lamb.
Wife’s Bra Size: just right.

The roof is 600 sf, rectangular, flat roof. We’re sloping to drains on one side at 1/4" to 1’-0". It’s new construction on TJI joists, with constructed plywood drain slopes.

The redwood+ipe decking is on 1/2 of the roof, the other half being 2" deep smooth round pebbles, and not walkable. We will have 10+ planters on both the deck and pebble areas.

The drains are 6"x6" through-parapet holes to drain buckets, with overflow scuppers next to them.

We’re very reluctant to go with a poured concrete solution (our fear is cracking and weight) or a welded stainless-steel pan (too complicated, and the pan can shift around.)

We’d prefer some elastic solution. I.e. modified bitumen, PVC, EPDM and the like.


#10

Don’t get the concrete concept…where you asking for an alternative to the redwood walking deck)? If so, then using light weight concrete pavers (with pedestals to level it- if desired) may be an alternative way to go…
Note: Regarding poured concrete over waterproofing…this is not maintenance friendly, certainly very costly and restrictive to homeowner and roofer regarding any future roof membrane repair and/or add-on of any future desired rooftop accessory/penetration

Additional item of note: Regarding the half of roof covered with ballast and additionally loaded with the weight the planters/soil & plants-I would certainly re-check to make sure building’s roof structure and it’s plywood deck substrate can adequately support this load

(P.S : You should put pavers in the ballasted areas where planter are located so that the homeowner can get to water and groom their plantings)


#11

Still voting for the 3-ply torched mod bit system. Like Cerberus said, make sure any decking etc. is modular or suffer maintenance issues later on.


#12

We always use IB PVC for decks like that. Did one in Brighton, MA a few years back. It was a walk-out patio/deck in the center of the house and had mod-bitumen with a drain in the center - basically a “swimming pool”. When we took it off, everything was wet/rotted under it. We put 80-mil IB there, and rebuilt the deck and never heard from the guy again. In roofing it is a good sign :slight_smile:

Epdm won’t really work, unless you have something like a 10x10 deck, where you can use a single piece of rubber. If you have seams, or a drain, than definitely PVC. Like someone mentioned, use wood fiber board (if you need insulation, put it under the fiber board} Also, put a few pieces of membrane where your deck rafters touch the main membrane. Some one mentioned building a deck out of “blocks” so when you need to repair, you dont have to tear off the wood. Well, that is one way to do it, but there may be movement of “blocks” which may damage the membrane. We built oure deck lake any other regular decks, but used screws. We also attached our framing orund the perimeter, so the deck is fixed - not moving.
Again, use thicker material (PVC). Check all yous seams. Terminate around the perimeter and you should be fine.

BTW, epdm is NOT heat welded - it is glued. That is why i do not recommend it.

Good luck.


#13

As long as its done right any flat roof system will work. The main thing is to protect it from traffic and install the posts that hold the deck up to the roof deck and flash them in. In lieu of resting it on top with a slip sheet. An insulation board with high density is also a must to protect the roofing from the deck fasteners. Epdm seams are taped not glued and are stronger than the sheet itself I would not worry about it at all even if some water sits on the roof it wont effect the membrane or the seams. Only asphalt systems are really affected by standing water but they stand up to traffic and abuse better than a single ply. Id say a multi layer mod bit would be the safest bet. And since the roof will be covered theres no reason for a white membrane at an added expense.


#14

hi all, i’m new here and all but i’m looking at building a garage onto my house and using epdm on the roof. Although it was touched on in this thread how do you actually add a deck ontop of the epdm? Is there a link somewhere? I would need a Gaurdrail around the perimeter (24x24). I’m sorry for hijacking the thread but I think this info would fit in this thread also rather than starting a new one. Thanks


#15

If the structure is built sturdy enough to hold the weight I think a ballasted epdm system using 2’x 2’ pavers would be a better choice than a wood deck. Easier to remove when theres a problem in the roof and a lot quicker to install. And probably a lot cheaper to. Plus its concrete so no sealing or maintenance required. The hand rail would either go into the fascia or pined to the pavers possibly to prevent roof penetrations.


#16

If the pavers shifted would this tear the epdm? are there special pavers available for this type of application, if so could you please provide a link so i could figure out a round about cost. Wonder if attaching the railing to the pavers would meet code, couldnt the whole railing essentially “fall” over? sorry for my ignorance, i’m just looking to get additional ideas and viewpoints before i call contractors. thanks again


#17

Railings make things a little more tricky. Some one mentioned in an earlier thread not to use slip-sheets, but instead suggested flashing the newl post and such into the roof. I personally disagree with that statement, as the fewer penetrations you make in the roof the better. Furthermore, wood is porous, so you wouldn’t want to terminate flashings around the base of exposed posts.

In your case, instead of using a railing, I would suggest a parapet. However, if you have to use a railing due to deed restrictions or such, then I suggest you either use a metal railing or construct a wood railing that sets on top of the roof. As for how to do it, I would need to know the particulars with regard to existing and new construction. Depending on how visible it is, you could set the posts in concrete or you could fasten them to concrete pavers, etc…


#18

Here is a link to Hanover Pavers. They make some nice pavers, but you can obviously get yours from Home Depot or where ever.

hanoverpavers.com/

As for fastening to the pavers, you would use steel L-brackets that would be fastened to both the posts and pavers. You might want to use multiple brackets on each post. You would screw the brackets into the base of each post, and secure brackets to pavers with something like Rawl Zamac Nail-ins. Understand the 2’x 2’x 2" pavers, especially the steel reinforced pavers, weigh around 90 pounds each. So, to blow the railing over would require winds that can flip over 90# pavers. If you need something more stable, you could install sleepers (I would suggest some Hardi-trim or maybe some “plastic-wood”) secured over top several pavers, and then secure the railing to the sleepers.

Once again, I would need to know the particulars.


#19

It certainly would


#20

[quote=“ROOFING MAVEN”]
It certainly would[/quote]

Do you mean meet code or fall over? In my case, this would be new construction of the garage so beefing it up to hold the weight shouldn’t be a problem since I didn’t break ground yet. However I’m pretty sure I would need a secure railing system on the roof to use it as a patio since i’m in a town that gets nit picked by “the man”. I currently have a raised deck with a doorway to it, I’m looking to build the garage attached to the house and keep my patio. My neighbors have this type of garage but don’t use the entire roof as a patio, they are an older couple, I however am a first time homeowner just out of college so i’ll have kids and dogs and … who knows what else on the patio at some time i’m sure. The neighbors have some ponding ontop but no leak problems, I’ll check out their railing system again i guess for a more detailed picture. I’m actually new to this type of work so links and detailed layouts help me immensely