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Discussion Starter · #1 ·
I need to replace a small concrete deck slab. It's a 2nd-floor entry deck for 4 condos; an 8' x 8' slab, 3 1/2 inch thick, supported on 3/4 ply over joists 2' O.C. After we do our work with the framing, I need to replace the concrete, including finishing with a slight slope for drainage; broom finish. The existing aggregate is pea gravel. The lumberyard right down the street mixes up towable 1-yard buckets. What should I tell them I want? Any recommendation about rebar or mesh?

Thanks,

Bob
 

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CarpenterSFO said:
I need to replace a small concrete deck slab. It's a 2nd-floor entry deck for 4 condos; an 8' x 8' slab, 3 1/2 inch thick, supported on 3/4 ply over joists 2' O.C. After we do our work with the framing, I need to replace the concrete, including finishing with a slight slope for drainage; broom finish. The existing aggregate is pea gravel. The lumberyard right down the street mixes up towable 1-yard buckets. What should I tell them I want? Any recommendation about rebar or mesh? Thanks, Bob
I would go with 2500 pea gravel with mesh. Are going to pump it in?
 

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It's less than a yard, moved about 50ft from the parking lot - I'm thinking a couple guys with buckets will be done in no time.
As long as it's not ME having to carry and climb the steps with those heavy buckets.... :blink: :no: :laughing:
 

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Bob, did I read this correctly in that this deck will be permanently supported by framing?

Are the floors in between living spaces concrete so as you drill into the ledger with some rebar 12 to 18 inches o.c.?

If indeed you end up using the lumber yard, you may want to consider paying the cost of an extra sack of concrete into the mix. It will help a lot with finishing for many reasons.

Also what kind of railing system will this have installed onto it afterwards?
 

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I'd put a mat of 1/2" rebar @ 1' centers.

Are you adding a waterproof membrane over the ply and framing?

I would also install some sort of expansion around the perimeter, something simple like the foam sill seal, then caulk the joint.

I never pour anything less than a 3,000 mix.

We would end up with the bucket method as well on something that small, might even use bag mix.
 

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What should I tell them I want? Any recommendation about rebar or mesh?
Either replace it exactly as it was OR check fire rated assemblies for options. From your post, it seems like a required egress, so there would be a fire rating required. Off the top of my head, I think that requires a 45 minute rating. I don't think it's going to be a problem, but I've been wrong before:whistling

.
 

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Discussion Starter · #10 ·
Bob, did I read this correctly in that this deck will be permanently supported by framing?

Are the floors in between living spaces concrete so as you drill into the ledger with some rebar 12 to 18 inches o.c.?

If indeed you end up using the lumber yard, you may want to consider paying the cost of an extra sack of concrete into the mix. It will help a lot with finishing for many reasons.

Also what kind of railing system will this have installed onto it afterwards?
No other concrete to attach to. Everything else is wood, all around, mostly rotted, which is why I'm there. The concrete pad lasted about 40 years, while everything around it rotted away: the structure underneath and good parts of the 2 buildings served by the deck. More cement in the mix - yes. I'm completely unconcerned about the cost of the concrete - anything to make it easier to handle and finish.
 

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Discussion Starter · #13 · (Edited)
I thought I had pictures. The deck spans between 2 buildings; the joists cross the span, 2x8, 2' on center, tripled up at the edges, bearing on the double plates on either side. On one side, you could do the demo with your hands - just punch a hole in the ply T&G siding and wrestle some studs and doors out of the wall. You could then work your way, Amazing-Hulk-style, several feet into the intersecting wall between units.

About 40% of the cost of the work consists of keeping access 24x7 for all 8 affected units (4 on the deck, 4 below).

This is strictly about repairing in-place, in-kind. Nothing meets current code. Nothing, so we're going to replace just as it was.

Tom: Yep, expansion strips, caulk, and flashing, all to be re-done. Flashing and water management generally were done wrong in the development in the first place (about 40 years ago) and subsequent repairs and replacements were a joke, usually without any flashing.

Membrane: I've been working my way through the remainder of a roll of Stego wrap from another job, so that will go under the concrete, unless someone has a better idea about the membrane (bituthene?). Flashing and other details will hide the bright yellow if I use the Stego wrap.

Lightweight concrete: Does that mean telling the yard I want lightweight aggregate? It couldn't hurt to lighten the load on the structure. Is there any other effect I should worry about (weaker, harder to finish? looks weird?). In the big picture, the cost of the concrete means nothing.

I appreciate the help.

- Bob
 

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This is strictly about repairing in-place, in-kind. Nothing meets current code. Nothing, so we're going to replace just as it was.

- Bob
Your license doesn't require you to bring it up to code at this point?

Do I have a fundamental misunderstanding about this being a pretty common requirement from state to state? (This is, of course, entirely possible. I fundamentally misunderstand a lot of s*&t)
 

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Around here, you can repair it every few decades for 100 years - it's grandfathered. Tear off and redo means bring it up to code. There are plenty of stairs in old houses that will just be repaired....
 

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Discussion Starter · #16 · (Edited)
Your license doesn't require you to bring it up to code at this point?

Do I have a fundamental misunderstanding about this being a pretty common requirement from state to state? (This is, of course, entirely possible. I fundamentally misunderstand a lot of s*&t)
Thanks, that's a valid question. It's not a licensing question as much as a code question, and the California Building Code (and the IBC, upon which it's based) discuss that question for about 50 pages in Chapter 34 - Existing Structures. The main relevant section for this project and for many repair projects in general, is this:

"CBC3412.2.4 Alterations and repairs. An existing building or portion thereof, which does not comply with the requirements of this code for new construction, shall not be altered or repaired in such a manner that results in the building being less safe or sanitary than such building is currently. If, in the alteration or repair, the current level of safety or sanitation is to be reduced, the portion altered or repaired shall [get fixed up to current code]."

In other words, you don't need to upgrade it, if the repair process doesn't downgrade it first. If you want to keep the open-riser steps, detach them from the deck and shore them up independently, for example. For this and similar projects, we're careful to keep the building accessible and safe, with only minimal interruptions. We'll ask the residents to be cooperative with us, but if someone really needs to get in or out of their unit while we're pouring a new deck, we'll make it happen. 100% of the rest of the time, residents will be free to come and go from their units, with maybe a 30 second wait while we turn off tools, put down a piece of ply, and make sure they're safe. That's why I'm the one doing this job, and not some hack.

Edit: As usual, someone else (hdavis) managed to say in 20 words what I said in 400.
 

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Back to one of the questions. Lightweight concrete is fairly often used for this application. I haven't worked with any in this application, but they come up in fire resistive deck design pretty often - there are a few proprietary products you can eventually find in the UL listings.

I'm not sure how badly light weight holds moisture, and in contact with wood, I'd want to understand that before deciding. I know of 3 ways to get light weight - air entrainment, perlite mix, and vermiculite mix. There may be others. I'd post the question over on the mason forum, and see what they know.
 

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4,000 PSI is pretty much my standby for all work except footers.

Gives you lots of cream for finishing and if you end up with a hot load it should still be strong enough when cured.
 

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I need to replace a small concrete deck slab. It's a 2nd-floor entry deck for 4 condos; an 8' x 8' slab, 3 1/2 inch thick, supported on 3/4 ply over joists 2' O.C. After we do our work with the framing, I need to replace the concrete, including finishing with a slight slope for drainage; broom finish. The existing aggregate is pea gravel. The lumberyard right down the street mixes up towable 1-yard buckets. What should I tell them I want? Any recommendation about rebar or mesh?

Thanks,

Bob
Bob, I would use corrugated steel deck. It is much better structurally then plywood and it will outperform the life span. Cost wise it will be about the same if not better.
 
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