We are in the design stages of a three story addition off the back of our DC rowhouse. I've posted posted a number of threads along the way looking for help and have received excellent advice. Thanks! We're nearing the end of the design stage with the architect and I've got some questions, hoping to benefit from the collective wisdom of the forum here. Just so everyone knows, I've met with the City at an earlier phase and they see no problems with the project.

There's lots of quirky aspects to this project, but there's one big one. There is currently a 6' high double wythe brick privacy wall separating my property from my neighbor's, it runs right down the property line and the neighbor is adamant that we not remove it (even though legally we can). We've had an SE confirm that it is structurally strong enough for us to build on top of it, but legally we can only build on top of our half. The architect has devised this ledger system.

It is also probably important to note that all joists and rafters run north south so that most the loads are taken to the south wall where there's a typical deep footing. The architect has also included a 6x6 post at the west end of that south wall, which the ledgers will connect to, hoping to also take some of that load away from the west wall. The west wall is 2x4 framing all 3 levels and the south wall is 2x6 all 3 levels, to better carry the roof loads. The west wall “cantilevers” off the existing brick party wall with a 2x10 ledger. The ledger is continuous to the southwest 6x6 post.

So, it all looks pretty ingenious to me, but will it work? Thoughts, opinions, concerns? All would be appreciated.

The 6 X 6 is going to be continuous to the top,how are you going to join sections?

The plans show that the 'siding'? Is going further than the property line?(Code?)

Insulation for the lower walls,'spray foam'?, if you are furring this out,you can use thin batts,or foam board glued to the walls.

The roof is flat, shingles won't work on a flat roof,even with 2 layers of felt.

It's early,, others will add to this soon:)

Thanks KBC.

I think the architect is calling for the 6x6 to be used basically as a stud in the outer corner on all 3 floors. Does that make more sense? Not meant to be a continues 6x6 from bottom on up.

How does it show the siding going past the property line... I am not seeing it. There is a strange restriction that if I want to build in this area, I must go precisely to the property line, not over, of course, but also not under!

We're only furring out those lower walls with 2x2s. It is a very tight space, less than 5x10. So, we figured the spray foam would give us the biggest bang for our buck!

The roof is one of the areas where the architect and I have disagreed. The roof is a 2:12 pitch, so not totally flat and there are plenty of shingles rated for use on a 2:12 pitch roof. Also, it doesn't show it on that drawing, but she is calling for 2 layers of #15 felt AND for the whole roof to be covered in ice and water shield. Also, rather than vent the attic space there, we'll be seeing the roof by spraying the bottom of the roof sheathing with spray foam, an accepted practice here. Are shingles really the wrong way to go here? She's fairly insistent.

I can post addition pages of the plans if helpful... or if this becomes a fun exercise for the community.

Thanks!

This is always fun for (me anyway), and to see what others comments are, we all learn from each other:)

To make a continuous post(which then would be the actual top to bottom weight carrier),I have half lapped the ends(18 inches) and driven pegs through(2) at each joint, I think by stopping at each floor and adding the post on top of a floor wouldn't be needed,you could just box out the corner with 2 X 6 and make the same strength.(perhaps even stronger,as opposing grains add more to the integrity)

Spray foam, I am only familiar with small amounts,perhaps you have a larger application I am not familiar with?

2:12 pitch and shingle,, never been a big shingle person below 4:12, perhaps rolled style roofing,but never shingle.(perhaps we have a semantics problem, your 'shingle' might be my rolled? )

4/A23,Ledger view.

The stud wall is not fully bearing on the brick divider?

So, regarding the 6x6 issue, as it is currently drawn, is it effective? Or not really doing much?

Yeah, around here they use spray foam for everything, you get about R-7/inch, so in older masonry homes it gets used a lot, really seals things up, using a lot less space.

Not an issue of semantics, she's calling for asphalt shingles. That said, the IBC says, "1507.2.2 Slope. Asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17 percent slope) or greater. For roof slopes from two units vertical in 12 units horizontal (17 percent slope) up to four units vertical in 12 units horizontal (33 percent slope), double underlayment application is required in accordance with Section 1507.2.8." And the shingle manufacturer's are OK with it. I am not sure why she wants shingles, should ask her though/

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Originally Posted by Stubits

So, regarding the 6x6 issue, as it is currently drawn, is it effective? Or not really doing much?

Yeah, around here they use spray foam for everything, you get about R-7/inch, so in older masonry homes it gets used a lot, really seals things up, using a lot less space.

Not an issue of semantics, she's calling for asphalt shingles. That said, the IBC says, "1507.2.2 Slope. Asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17 percent slope) or greater. For roof slopes from two units vertical in 12 units horizontal (17 percent slope) up to four units vertical in 12 units horizontal (33 percent slope), double underlayment application is required in accordance with Section 1507.2.8." And the shingle manufacturer's are OK with it. I am not sure why she wants shingles, should ask her though/

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Yeah,, seriously, think about the logistics.If water,standing at 2:12 and doesn't run off a shingle,it gets trapped below each overlapping shingle, where are the nails? right where this water is going to sit, I have repaired many many roofs that have not enough pitch, even with Ice and Water shield, where the nails are rotted,the water runs down the holes through the base paper, Imagine 80 holes in this roof in 10 years,, where do you plug the leak?

Go for something like a solid sheet,Torch-down,rubber, anything actually designed for low pitch roofs.

The 6 X 6, ask for a closer commentary from her about the need for this, separate floors with only the flooring/floor joists to support the next 6 X 6, that isn't right... you could use 2 X6's and make it just as strong.

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We're only furring out those lower walls with 2x2s.

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Why 2x2?

I think I saw a note that says all material on exterior walls will be treated material. If you find a treated 2x2 it will be as crooked as a snakes trail. Carpenter will probably have to rip a 2x4 down to make a 2x2. It will also probably split if you try to shoot it to the brick wall to make or keep it straight.

Why not just use a 2x4 turned flat to the brick wall.

Harold, that makes perfect sense. My only thought would be that using 2x2 allows for more insulation, but you're right, seems like a logistical mess!

On the 6x6 and the ledger and the like, here's what my architect has to say:

"All joists and rafters run north south so that most the loads are taken to the south wall where we show a typical deep footing. I also show a 6x6 post at the west end of that south wall, which the ledgers will connect to, hoping to also take some of that load away from the west wall. The west wall is 2x4 framing all 3 levels and the south wall is 2x6 all 3 levels, to better carry the roof loads. The west wall “cantilevers” off the existing brick party wall with ledgers. There is a 2x10 ledger at each of the 2 heights in the brick wall. The ledgers are continuous to the southwest 6x6 post."

Does that make more sense than my explanation? Will it work they way she is describing it?

I guess I am also curious about

1) The only load that the turned-down footing on the west side was intended to bear is the wall on the basement level, however the sheathing and siding is continuous to the other levels which load onto the side existing brick walls. Does there need to be some sort of separation or expansion joint between the top plate of the basement wall? Or should we not worry about this idea of bridging and just let the west wall carry all that load?

2) Is it okay for a turned down slab to butt into a deep footing, or do I need to ask the architect to add more notes about how to make that connection?

Thanks!

Bump