Concrete against rim joist ???

[2manyrocks]

I just finished replacing this section of rim joist with pressure treated material. The original porch concrete was apparently butted against the untreated joists which had completely rotted away plus I found active termites that I sprayed. Although there was tar paper and galvanized sheet metal under the shingle siding next to this area, there wasn't any between the concrete and the rim joists themselves. It appeared as if this area had been patched at least once if not twice before in the 75 year history of the house.

There is no porch roof and the overhang is so short that there isn't really any protection against rain.

The old concrete landing was spalling. I couldn't figure out how to get the new rim joist in without tearing out the concrete landing. So I removed the landing to replace the rim joists and now I have to figure out how to proceed.

I am considering three options. 1). Tear off the entire porch and close in the door with a window and siding. The issue would be that the door trim is wider than other existing windows and it would look odd unless I recut and redo what I suspect may be asbestos siding. There is also some decorative trimwork at the top of the door that would have to be removed to make the opening match the existing windows. So this option is not that appealing, even though it would make functional sense because the doorway never gets used and there wouldn't be any more issues with the little porch.

2) Take the porch down a bit lower, tear off the steps to get the step riser height adjusted to the new landing height, and repour the landing and steps below sill level. This would be more work involving roughly double the amount of concrete to redo the steps not to mention the form work for the steps. And I would have a landing that is more than 7 3/4 inches below the interior floor level. I would guess option 2 would be double the work of option 3, but there wouldn't be any concrete against the rim joists.

3) Keep the existing steps, repour the landing against the rim joists, but flash the rim joist with rubber tape sealant and galvanized sheet metal. The form for the concrete would be relatively easy, and this would look like the least amount of work overall. What I don't want is for the rim joists to rot again and then have to remove all this new concrete. I saw one suggestion to leave an air gap between the concrete and the rim joist, but it just seems to me that this would just be an open pocket for rain to run into making the situation even worse.

If a gap would help, I have a section of galvanized C channel that I could insert between the rim joist and the concrete that would separate the two. The C channel would close off the top, but would be open in the center so hopefully it wouldn't let in as much rain as an air gap that was totally open The C channel is only 6" tall so I would have to come up with some kind of other filler to make up what I think will be a 7 1/4" thick landing.

I've looked on-line about how to do this, but I am not sure what I should really do.

Thoughts?

 

[3Ts]

I think you're right about that siding being asbestos, so you don't want to modify that.

I think your option 3 with the pressure treated rim joist, rubber tape, and galvanized steel should work fine. You will need to caulk it to keep the water out so it doesn't corrode the galvanized steel.

If I were doing it, I would use a pressure treated rim board, cover that with the butyl tape, then the galvanized flashing to protect the tape. Then I would use a foam expansion board (see link) as a spacer when you pour the concrete. Once the concrete cures, I'd remove the tear off strip and use a concrete caulk to cover the gap.

The rubber strip and foam board can be had in single rolls, but they're 50' or so. It looks like you only need about 5'. I can't tell how wide you need it to be, but they come in various widths.

I'm sending you a PM.

Foam expansion board

 

[MossRoad]

We had a similar situation with our front steps to our front porch when we bought this house. We ended up having the front steps jackhammered down enough to be able to slip a set of precast concrete steps over the old steps. That allowed us to install siding all the way across the front of the porch under the door. The steps slid right up to the siding. There's about a 1" gap between the house and the top landing.

Similar to this, but with a larger landing at the top. They just backed up the truck and set it in place.

Just something to consider.

 

[MasseyFerg231]

Use a dimpled drainage mat against the wood and re pour steps/landing. Leave a step down is possible. Once completed is a good quality sealant such as NP2 along the top of the dimpled drainage mat to help seal the joint and keep it clean.

 

[2manyrocks]

So far it seems there is consensus for a gap.

Prefab steps would be great. There are some big trees in the way of a delivery truck. So I think I am stuck having to use my cement mixer.

 

[MasseyFerg231]

Something like this;

ArmorDrain 110 Drainage Mat - Mar-flex Waterproofing & Building Products

ArmorDrain 110 Drainage Mat is designed to allow water to drain through channels created by the dimpled core, while protecting a foundation’s primary waterproofing membrane from damage by soil and sediment.

mar-flex.com

NP2 link

MasterSeal NP 2 | Polyurethane Sealant | Master Builders Solutions

Learn about MasterSeal NP 2, a multi-component, polyurethane sealant that has been successfully tested for joint movement of +/- 25% and can be tinted to multiple colors.

www.master-builders-solutions.com

 

[s219]

Can you just frame in a landing with lumber, then deck it with wood or composite? For that matter, just build a whole new porch out of lumber if that concrete is beyond saving.

 

[2manyrocks]

The steps and sides of the porch are still solid. I figured it would be more work to tear out the rest of what's left plus a new concrete landing would outlast a wood landing if I can correctly flash the landing so the rim joists don't rot again.

One way I know would have to work would be to knock the landing further down below sill level and then add a metal grated step. I saw one at the junkyard. Not sure what it would cost me. If I knock the landing further down, I won't be able to salvage the existing steps. Then i'd have to build forms for the steps and repour them which roughly doubles my labor.

So if I can find a way to repour the old landing, that seems to be the least labor and least material if I can flash it so the rim joists don't rot again.

As for working with expansion foam to create an air space vs the dimpled membrane, the dimpled membrane drain mat that Lowes carries is something like $120 for a 4 x20 sheet. https://www.lowes.com/pd/NDS-4-ft-x-25-ft-Sheet-Drain/5001920851 Expansion joint material seems to be less expensive, but isn't in stock locally. https://www.lowes.com/pd/Reflectix-...lyolefin-Concrete-Expansion-Joints/1001003194

I wonder if corrugated plastic might be another option for creating an air space between the joists and the new concrete? But it doesn't seem any less expensive. https://www.lowes.com/pd/Coroplast-...n-L-White-Corrugated-Plastic-Sheet/1001469536

I have a tree service coming to cut some overhanging trees this week so I'll have to deal with that and can't safely work on the steps with them working in the same area. I'd rather think this through and do it once than ever do this again.

edit: Just mentioning this for anyone else facing a similar issue. I've read that natural stone does not absorb water like concrete. Another option for consideration might be to cap the landing with natural stone.

 

[2manyrocks]

I removed enough fill stones from the existing porch to create a space in which to mortar a stone landing. I picked up some flat limestone from around the property and mortared it in place as a landing that roughly matches the existing limestone foundation.

Fitting the stones together in any sort of pattern took me about 12+ hours. I could have poured cement in probably 2 hours. I don't think the stone landing will be as durable as concrete would have been, but it wouldn't be that difficult to pour a concrete cap over this later if it comes to it.

My thought process was to keep any masonry work below the rim joist so this doesn't trap moisture in the future. The rim joist has been replaced at least three times at this point. It was very evident that the rot matched the old concrete porch landing plus an additional few inches on either side where the water was running off. The porch isn't used as a means of ingress and egress. I don't want to do this project ever again. So I look the conservative approach and decided to drop the landing below the rim joist in my particular situation.

The new concrete pad and stand is for a future mini split HVAC. I didn't do a great job on finishing the concrete pad. It was probably for the best that I didn't pour a concrete landing judging by the roughness of the pad.

Thank you all for your help and kind suggestions.