Attaching posts to a waterproof deck.

[5.4MarkVIII]

I know we have some deck pros on here.
we have, what was a covered deck off the master bedroom. Under the deck is actual basement. It’s on an outside corner. So the two railing sides are directly above cinder block walls the other two sides are walls. (If that makes sense)

The “decking” is out door carpet which appears to be glued to some sort of rubber but I have not yet pulled up any of the decking.

I did however discover that the existing rails were originally only about 2 and a half feet up. And then Apparently the PO wanted to cover it so just stuck another 4x4 post on top of the existing hand rail.

It was sketchy . So I’m re doing it. Ive done a couple decks before and helped my did with a couple as well but I have never done one on top of a waterproof surface. Just wondering what the best Method is to attach the new vertical posts to hold the roof and handrails. Currently is just a 2x4 block nailed threw the membrane and then The 4x4 post screwed to that.

Also what would the life expectancy of this water proof roof be? Never had a leak. But wondering if it’s a good idea to have it inspected or even replaced before I build a new deck on top.

It’s in really good shape being that it was a covered deck.

Thanks gents.

[Laffs]

Any photos?

Are you saying the carpet is glued to a rubber membrane or referring to the rubber backer of the outdoor carpet? What's the substrate underneath the carpet?

[5.4MarkVIII]

Any photos?

Are you saying the carpet is glued to a rubber membrane or referring to the rubber backer of the outdoor carpet? What's the substrate underneath the carpet?

I’ll get some pictures. Rubber looked to be separate from the carpet. It’s black and maybe a 1/16 the thick and then the carpet seems to be glued to it.

I’m not 100% sure of the substrate. Since it’s closed in below.

[Laffs]

I’ll get some pictures. Rubber looked to be separate from the carpet. It’s black and maybe a 1/16 the thick and then the carpet seems to be glued to it.

I’m not 100% sure of the substrate. Since it’s closed in below.

Might be EPDM Rubber which is a really good thing for you if it is. Give me 10 min I'll take a photo of some on the roll in my shop.

[5.4MarkVIII]

IMG_6650.jpgIMG_6648.jpgIMG_6649.jpg

deck is roughly 10 feet deep and 14 feet wide.

this next picture is how they attached the originally corner post. on closer inspection the carpet is newer than the wood structure. so im thinking they cut the posts to get the new carpet under and then blocked the posts back up again. is there a better way to fasten the posts threw the membrane or is it just screws and caulk?
IMG_6647.jpg

this is about all i can see of the membrane. almost looks like shingle material but seems much more pliable.
IMG_6651.jpg

[Laffs]

Ah fuck that looks like Mod Bit.

[Laffs]

Ok so attached are two different roofing system samples.

First one (the granulated roll) is whats called Mod Bit or Modified Bitumen. It's a base and a cap sheet normally torch applied to the substrate.

Second one is the rubber membrane called EPDM. It's normally fastened down with screws at the seams or fully adhered.

Based on the pic you send I'm guess it's Mod Bit you have up there.

[5.4MarkVIII]

what kind of life span could one expect from something like this if it was carpeted and covered from the elements?

[Laffs]

If it's Mod Bit the proper way to do this would be
-cut the roof out to the substrate
-attach the post base to the wood or concrete
-drop your 4x4 in the base
-add cant strip (45 degree angled wood blocking) to the perimeter of the post
-bring new base and cap sheet up the post a few inchs
-add 3 course mastic/mesh to the corners and granules
-apply a new metal counter flashings to where the roofing ends with a water cutoff mastic

Improper way that might work would be scrape the area, screw the post base directly overtop the mod, install the post, 3 course mastic and mesh the post base in to the roof field. Kinda ugly but "should seal"

If its EPDM its

-cut the roof out to the substrate
-attach the post base to the wood or concrete
-drop your 4x4 in the base
-clean perimeter of the penetration with weathered membrane cleaner
-prime area
-apply a prefab square pipe boot with tape, roll it in to membrane
-lap seal perimeter.

Either case, I'd probably say fuck it and lag my new railing posts in to the wood fascia of the deck, then seal the area of the old posts.

[Laffs]

what kind of life span could one expect from something like this if it was carpeted and covered from the elements?

Honestly can't say I've seen a Mod with carpet glued to it, so really operating outside the manufacturers recommendations there. Normal conditions 20-25 years is acceptable, your details where it meets the walls of the house and door will likely fail and leak first before the field.

When you go to replace it I'd recommend the newer style decorative TPO/PVC membranes. They can be glued directly to plywood, have pre made factory accessory post bases, and won't require you to put carpet or anything over top. We use Global Decking/Deck King (Pic attached, theres more finish options beyond the fake rocks or fake wood in our sample but no one ever puts the fucking samples back) for patios like this all the time, good products. Any other flat roofing system will require you to do XPS or pedestals to put any type of deck board/paver over top which will drastically raise the finished floor height and fuck with your transitions.