# Deck Tiles Over Modified Bitumen Flat Roof



## seurban (May 11, 2018)

Has anyone had any experience with click-together roof tiles over a modified bitumen flat roof?

Last year we redid a large (~18’x20’) flat roof on our house and, since it has access from our office (and possibly some new outdoor stairs) we’d like to be able to use it as a roof-top deck. The roof is two layers of modified bitumen with white granules on top (stones about 1 mm square). SEE PICTURE? We chose this because the roofer said it would hold up to some foot traffic and possibly furniture, but now we’re unsure if that will be durable enough on its own and may want to upgrade the look and feel (and would appreciate not tracking those granules inside).

Ideally, I’d like something resembling a wood or composite deck, but a lot of the solutions we’ve come across are tall and the threshold to the office is only about 2.5” above the roof. Those products are also pretty expensive, so I’m wondering if we could use click-together style deck tiles like the attached picture. They’re composite slats on top and black plastic standoffs on the bottom. They seem like a good solution (and relatively cheap), but I’m a little worried that weight might get concentrated on too-small standoffs and damage the roof. Any advice on whether these can work?

We did some more poking around and found the company Great Mats that recommended 2” rubber tiles (the attached all black picture shows the underside), the threshold to the office would become a little too short for comfort with tiles that actually measure ~2 1/8” (leaving ~3/8”, we got a sample). We’re also not wild about adding that much weight to the roof, or paying to ship it to us. 

Another option from them are thinner PVC tiles (blueish pic showing the underside) that list rubber roofs as something they can go over, but when we mentioned the specific type of roof we have they pointed us to the previous tiles without an explanation why. Any thoughts as to whether these tiles would actually work or why not? A possibly similar option are polypropylene tiles (the tan pic).


FYI my home was built in 1930 and is in the Cleveland, Ohio area so it will see snow as well as some reasonably hot summer days. The deck is also located near some trees, so it gets its fair share of buds in the spring and leaves in the fall.


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## seurban (May 11, 2018)

Links to products I mentioned:

Click together composite tiles: https://www.wayfair.com/home-improvement/pdp/newtechwood-naturale-composite-12-x-12-interlocking-deck-tiles-in-canadian-maple-ntwd1025.html
2" Rubber tiles: https://www.greatmats.com/tiles/sterling-patio-rubber-tile-2gray.php
PVC tiles: https://www.greatmats.com/tiles/decking-tiles.php
Polypropylene tiles: https://www.wayfair.com/home-improvement/pdp/mats-inc-bergo-15-x-15-polypropylene-loose-laysnap-in-tiles-in-cedar-mwf1271.html


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## Talos4 (Aug 10, 2006)

A "floating" deck over a MB roof membrane is not ideal. I wouldn't recommend it. Granulated or not. 

The granules are used for two reasons: Protection of the membrane from UV degradation and aesthetics. 

The MB membrane is always going to remain "soft" and pliable it's how it's designed. 
As the membrane warms either due to direct sunlight or warmer temperatures it will more susceptible to point load punctures. 

Point loads would be furniture legs, corners of the tiles (as people walk over them), grills, the heels of many shoes etc.

An 80 mil single ply membrane would have been the best choice if the intention all along was to put on a floating deck. Many options are available for materials/methods including all of the ones you list above.

You really have one viable option to accomplish your idea. The use of asphalt based walkway pads. See below for an example.

https://www.apoc.com/products/roof-accessories-dek-top-walkway-pads-apoc-5040

You should check with local roofing supply houses such as ABC Supply, Allied, Beacon etc, for what they carry. These typically come in 2'x4' or 3'x4' sizes. 
anywhere from 1/2" thick to 1" thick. I'm pretty sure the local big boxes would not carry these. I may be wrong though. 

Not all suppliers sell retail, although I do know that ABC supply does and will sell in quantities smaller than full pallet loads typically ordered by contractors.


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## RollBlueTide (Jan 29, 2021)

seurban said:


> Has anyone had any experience with click-together roof tiles over a modified bitumen flat roof?
> 
> Last year we redid a large (~18’x20’) flat roof on our house and, since it has access from our office (and possibly some new outdoor stairs) we’d like to be able to use it as a roof-top deck. The roof is two layers of modified bitumen with white granules on top (stones about 1 mm square). SEE PICTURE? We chose this because the roofer said it would hold up to some foot traffic and possibly furniture, but now we’re unsure if that will be durable enough on its own and may want to upgrade the look and feel (and would appreciate not tracking those granules inside).
> 
> ...





seurban said:


> Has anyone had any experience with click-together roof tiles over a modified bitumen flat roof?
> 
> Last year we redid a large (~18’x20’) flat roof on our house and, since it has access from our office (and possibly some new outdoor stairs) we’d like to be able to use it as a roof-top deck. The roof is two layers of modified bitumen with white granules on top (stones about 1 mm square). SEE PICTURE? We chose this because the roofer said it would hold up to some foot traffic and possibly furniture, but now we’re unsure if that will be durable enough on its own and may want to upgrade the look and feel (and would appreciate not tracking those granules inside).
> 
> ...


I was wondering what rooftop surface you went with.

I am wanting to do this same exact thing over a roof that is the same material and saw the same Great Mats you are considering.

Due to cost and weight I am considering Staylock perforated tiles that are blueish in your picture. 

Thank you, I hope I can hear back on what you did!


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