i was recently elected to be head of building maintenance for our cooperative, and the first project i'd like to take on is a tricky one. our townhouses are steel frame and continuous concrete slab construction. the first floor slab extends beyond the enclosed perimeter wall of the unit to create the outside front step. unfortunately the architect who designed this place forgot to put a waterproofing layer in the slab and over the years water has seeped down through cracks in the concrete to the steel decking below and it has started to rust. we need to replace the decking in the next couple years or the slab will eventually fail.
i would prefer not to have to cut the slab out completely and pour a new one. many of the units have finished basements and pouring a new slab would be very messy, disruptive and expensive. the fix i'm proposing would be to cut a large sheet of decking to cover the rusted area from below and weld it to the existing deck. then i'd like to grind or saw cut a couple inches of concrete from the slab above to expose the cracks, fill them with epoxy, lay down a new waterproofing layer, and add a concrete topping. i've talked to a couple architects about my plan, and they advise to just suck it up replace the slab in that area. it's a better long term solution.
so i've made a little headway with this since my original post. a number of architects i've talked to claim that the steel deck is not structural - just a form for the concrete. i'm not so sure of this, but if this is true, replacing the steel deck would not make a whole lot of difference, just a cosmetic fix to cover up the rust.
we also had an interesting lunch and learn on zypex, a waterproofing concrete admixture or top coating. i'm now tempted to try grinding down an inch or two of the concrete, patching the cracks with epoxy or a xypex mix, then adding a xypex topping with sealer.
yeah, i would replace the slab. how tall is your building? are you going to need a crane to do this job? will the builders have to take the deck in through the door sheet by sheet? will you need a concrete pump? it sounds like this is going to be an intrusive operation either way.
another important consideration is who is managing the liability for the project. considering that this is a structural issue, your bound to hire an engineer at some point, and likely one who has run into this issue before. sometimes its best to get an engineer or even an experienced construction manager involved right way to make the proper recommendations.
the deck is usually structural, depending on how far it spans. metal deck floors w/ concrete topping are usually a composite system; the steel and the concrete work together in a way that you can't have one without the other. sometimes these slabs are also unreinforced, depending on the size of the deck and whether or not you have headed anchor studs piercing the deck to attach the concrete to the framing below.
one of the big issues that you are running into, in a humid climate, is that once you have significant rust you can't get rid of it. you could try sandblasting the rust off of the bottom of your deck, but i wouldn't doubt it if your deck is also rusting from the inside, and any h.a.s. or w.w.m. or rebar that's reinforcing your slab needs to be replaced as well. i'm obviously guessing, but my educated assumption is that that slab is coming out.
it's several two-story townhouses each unit with a shared front stoop. to replace the slab entirely, you would have to remove the door frame, a three by eight side light, and a good portion of the interior finish floor (in addition to the concrete stoop). the biggest problem i see with completely replacing the slab is how to support the new slab. the existing slab is cantilevering off a beam, therefore we would have to build a new support system for the replacement slab.
you're right that if there is rebar in there which i imagine there is it's probably as rusty as the deck below, but my thinking is that if you can prevent anymore water from attacking the steel, there should be enough structural integrity in the steel to keep the slab supported and not go to the great expense and hassle of completely replacing the slab.
we have western waterproofing doing the concrete work. they're good peeps. they started work on one of the units today. i'm anxious to go home and see how the cracks look after they've taken off the first inch or two of concrete.
you're probably right about talking to a structural engineer. from my experience though structural engineers are number crunchers, and this isn't really a number crunching problem. still it's worth a call in any case.
well, they are, but this is also a structural liability issue. a well seasoned structural engineer will be able to do an analysis on what shape your existing structure is in, and what exactly needs to be done with it. he can inspect welds and look for cracks and sags in places you won't think to look. it could be that the rust isn't an issue.
I've used the zypex before on th efaoundation of a house I owned it worked like a dream, it really is more of a patch strategy than an improvement for long term and if it gets any foot traffic etc I would agree with the full slab fix it sounds bad but once its done your good to go for a long time.
as some of you may know, the architect of these building was mies. last night, i got my hands on mylar copies of the original construction set for lafayette park. man, it was like having gold in my hands, truly astonishing the completeness and logic of the drawings in six sheets. here is the sheet layout as best as i can remember:
A-1 1/8" basement plan; concrete foundation details
A-2 1/8" first floor plan; sections at entry; interior elevations; door/room finish schedule
A-3 1/8" second floor plan; curtain wall details
A-4 1/8" elevations; exterior stair details
A-5 1/8" sections; 3/4" wall sections; wall section details
A-6 stair and stair details
that's it. the whole darn set in six less-is-more sheets. and the drafting on caldwell's landscape plans is gorgeous. i've never seen stippling quite like that before.
the best new detail gleaned from the set - mies didn't use flashing where the exterior wall meets the roof. instead he used a series of angles to create a drip edge over an angled wood blocking gravel stop. the angles create a very clean line without that ugly band of cap flashing you see on most buildings. great detail.
well, because i've received countless emails inquiring how this project turned out, here's the update. we decided that the steel deck was only minimally structural and that it's primary reason for being there was to provide a form for the concrete. we thus decided that it was more important to keep anymore water from getting at the deck, rusting through, and leaking onto our basement floors than it was to actually replace the deck.
thus we had the contractor remove an inch of concrete, fill any major cracks (sometimes using steel rods to close the crack first), replace the concrete, and use a waterproof seal top coat. the rusted decking underneath we kept in place and will decide later if it is worth replacing for cosmetic reasons.
the contractor was a pain in the ass. he added a grit finish to the sealant which wasn't listed in the scope of work. he claims it will make the surface less slick, but more likely i see it collecting dirt and being a maintenance nightmare (which has played itself out to be true). he also left the job site a mess with dust on all of our windows, streaks of concrete on our walls, and a very sloppy edge at the bottom of the sealant. he was only minimally responsive to our complaints. makes me wonder if most contractors truly care about the quality of their work or if they just want to get out of there as quick as possible to make every last red cent on a job regardless of quality. we're using/have used a different contractor for additional concrete/masonry work.
we did a test on my unit where we cut a sheet of decking that almost matched the profile of the existing decking (we could not find an exact match because the townhouses were constructed in 1957). we anchor bolted the new deck on top of the rusted portion of the existing deck and filled the gaps between the two decks with sealant. then repainted the area.
we believe it really is just a cosmetic fix (the new waterproof top coat is what's keeping the water out), so we're holding off on the expense of doing this to additional units.
he also left the job site a mess with dust on all of our windows, streaks of concrete on our walls...
my boss and i use to go to job sites about an hour before the scheduled contractor gets there so we can cover things up with plastic...i guess the lesson is never trust those guys to keep it clean.
no, it was actually a slightly higher bid, but we went with them based on reputation. i was surprised, but i think it reflects more on the guy who was in charge of this particular job than the company itself. we're still taking bids from them, but as long as this guy's in charge, i will have serious reservations about doing anything with them again.
we had some brick work done by a lesser known competing firm that did a beautiful job replacing portions of brick wall and a limestone coping. you really have to know your area well to find the best people.
I've only managed to find homeless people in my area well.
Sorry I joined the thread late..welcome to the thankless world of providing free time and service to your Condo/Co-op board. I gave up on mine. Glad to hear that things are working out, sort of.
ha, so true, poczatek, so true. i took over for an architect who had been doing this for about 5 years, older guy, experienced architect. at the annual board meeting, he announces that he's stepping down, but says he has the perfect replacement in mind and turns to me. i'm thinking, "oh, what an honor and such great experience for a young architect." little did i know all the unpaid hassles i had in store, but it has been generally a good experience.
...what did it for me was inevitable criticism and mixed bag of bad taste from the peanut gallery who would apparently rather be wallowing in mud than in the environment you will try so hard to improve for them. My building was a modern gem when built, and now is the eyesore of the neighborhood (a very wealthy neighborhood) after 40 years of mismanagement and systemic slum-lording by the former board/owners -Thankless Pigs! Anything we (reform board) tried to do was cutting into their rental profits. Made a couple of friends throughout the process with similar ambitions, so all was not lost.
Poz - same story in mine - we've been trying to replace the windows every year. It would have been 10k avg. per unit 4 yrs ago with building financing at great rate. Consistantly these slum lords who own whole chunks and live in Florida vote no. It drives down sales prices, drives out owner occupants, and is terrible for heating / cooling. They asked me twice to join the board I said no frigg'n way.
Poz - your buildings still pretty nice compared to others in the area. Just look at mine. I swear some bigtime developers gonna have it condemed and grab the land while these old people and slum lords squabble.
Oh - the latest revised pricing for windows is 17K per unit at higher rates
The most important thing for these Floridan Owner/Slumlords is keeping the Assessments Low. Some fucking idiot on our board (20 years ago) motioned to make windows each unit owners' responsibility (all in favor), so they have been intermittently replaced over the past 20 years in only about 30% of the units...completely hodgepodge. And like yours, the price to replace them has gone up considerably (about 15K per unit) I argued about the heat loss (70% of building is single pane steel sash painted shut) I tried to educate them on principle of make up air (carpeting and/or has sealed undercut doors) and so on...they just don't get it or care. I'm done!
well if our last proxy in October doesnt pass we'll be making windows each units responsibility. It adds 20% to cost per unit and will look like ass. Its a big $ hit to the windows, but the building finacing is better than anyone person could get, its a couple hundred a month extra for 5 years plus a down payment. I figured what i could rent it for and I'd still be positive 1-200 a month. Which means these pigs who've been paid off or have mortages from the early 80's are prob making $500 a month or more profit. If there was a way to limit absentee landlord vote share I think we could get it passed. I heard were 4 votes short.
As for low bidders - they low bid masonry wall 18'x100' on the alley in 1993. We just redid it all for 300K last year. Again low bid. So in 2020 we'll prob be doing it again. Assholes.
our coop recently replaced all of our single pane windows with double pane - about 40 townhouses of floor-to-ceiling glass. our monthly cooperative fees are very high ($750/month), but it does allow us to do necessary maintenance and upgrades.
cooperatives are absolutely impossible to maintain, particularly when the property is historically significant. when i think of all the stupid "improvements" that people have done to their townhouses, it makes me a little sick, but at the same time, you can't (and probably shouldn't) have too much say about others' taste or lifestyle unless it profoundly alters the integrity of the building itself.
replacing steel decking
i was recently elected to be head of building maintenance for our cooperative, and the first project i'd like to take on is a tricky one. our townhouses are steel frame and continuous concrete slab construction. the first floor slab extends beyond the enclosed perimeter wall of the unit to create the outside front step. unfortunately the architect who designed this place forgot to put a waterproofing layer in the slab and over the years water has seeped down through cracks in the concrete to the steel decking below and it has started to rust. we need to replace the decking in the next couple years or the slab will eventually fail.
i would prefer not to have to cut the slab out completely and pour a new one. many of the units have finished basements and pouring a new slab would be very messy, disruptive and expensive. the fix i'm proposing would be to cut a large sheet of decking to cover the rusted area from below and weld it to the existing deck. then i'd like to grind or saw cut a couple inches of concrete from the slab above to expose the cracks, fill them with epoxy, lay down a new waterproofing layer, and add a concrete topping. i've talked to a couple architects about my plan, and they advise to just suck it up replace the slab in that area. it's a better long term solution.
what are people's thoughts here?
agreed, replace the slab. 2-3 days work. but how are you going to secure it to the old slab? epoxy anchors?
all that sawcutting/on-site welding sound more expensive than replacing the slab...
so i've made a little headway with this since my original post. a number of architects i've talked to claim that the steel deck is not structural - just a form for the concrete. i'm not so sure of this, but if this is true, replacing the steel deck would not make a whole lot of difference, just a cosmetic fix to cover up the rust.
we also had an interesting lunch and learn on zypex, a waterproofing concrete admixture or top coating. i'm now tempted to try grinding down an inch or two of the concrete, patching the cracks with epoxy or a xypex mix, then adding a xypex topping with sealer.
yeah, i would replace the slab. how tall is your building? are you going to need a crane to do this job? will the builders have to take the deck in through the door sheet by sheet? will you need a concrete pump? it sounds like this is going to be an intrusive operation either way.
another important consideration is who is managing the liability for the project. considering that this is a structural issue, your bound to hire an engineer at some point, and likely one who has run into this issue before. sometimes its best to get an engineer or even an experienced construction manager involved right way to make the proper recommendations.
the deck is usually structural, depending on how far it spans. metal deck floors w/ concrete topping are usually a composite system; the steel and the concrete work together in a way that you can't have one without the other. sometimes these slabs are also unreinforced, depending on the size of the deck and whether or not you have headed anchor studs piercing the deck to attach the concrete to the framing below.
one of the big issues that you are running into, in a humid climate, is that once you have significant rust you can't get rid of it. you could try sandblasting the rust off of the bottom of your deck, but i wouldn't doubt it if your deck is also rusting from the inside, and any h.a.s. or w.w.m. or rebar that's reinforcing your slab needs to be replaced as well. i'm obviously guessing, but my educated assumption is that that slab is coming out.
it's several two-story townhouses each unit with a shared front stoop. to replace the slab entirely, you would have to remove the door frame, a three by eight side light, and a good portion of the interior finish floor (in addition to the concrete stoop). the biggest problem i see with completely replacing the slab is how to support the new slab. the existing slab is cantilevering off a beam, therefore we would have to build a new support system for the replacement slab.
you're right that if there is rebar in there which i imagine there is it's probably as rusty as the deck below, but my thinking is that if you can prevent anymore water from attacking the steel, there should be enough structural integrity in the steel to keep the slab supported and not go to the great expense and hassle of completely replacing the slab.
we have western waterproofing doing the concrete work. they're good peeps. they started work on one of the units today. i'm anxious to go home and see how the cracks look after they've taken off the first inch or two of concrete.
oops posted under my pseudonym. now the world knows.
yes, and i know where you live.
if i were you, as the head maintenance guy, i would still call an engineer either way. this really isn't an architect thing.
you're probably right about talking to a structural engineer. from my experience though structural engineers are number crunchers, and this isn't really a number crunching problem. still it's worth a call in any case.
well, they are, but this is also a structural liability issue. a well seasoned structural engineer will be able to do an analysis on what shape your existing structure is in, and what exactly needs to be done with it. he can inspect welds and look for cracks and sags in places you won't think to look. it could be that the rust isn't an issue.
I've used the zypex before on th efaoundation of a house I owned it worked like a dream, it really is more of a patch strategy than an improvement for long term and if it gets any foot traffic etc I would agree with the full slab fix it sounds bad but once its done your good to go for a long time.
as some of you may know, the architect of these building was mies. last night, i got my hands on mylar copies of the original construction set for lafayette park. man, it was like having gold in my hands, truly astonishing the completeness and logic of the drawings in six sheets. here is the sheet layout as best as i can remember:
A-1 1/8" basement plan; concrete foundation details
A-2 1/8" first floor plan; sections at entry; interior elevations; door/room finish schedule
A-3 1/8" second floor plan; curtain wall details
A-4 1/8" elevations; exterior stair details
A-5 1/8" sections; 3/4" wall sections; wall section details
A-6 stair and stair details
that's it. the whole darn set in six less-is-more sheets. and the drafting on caldwell's landscape plans is gorgeous. i've never seen stippling quite like that before.
the best new detail gleaned from the set - mies didn't use flashing where the exterior wall meets the roof. instead he used a series of angles to create a drip edge over an angled wood blocking gravel stop. the angles create a very clean line without that ugly band of cap flashing you see on most buildings. great detail.
huh. why don't you scan them in for us?
i'll have to check to see if there are any restrictions on reproduction, but definitely, if there's no issue there.
Whole construction document in six sheets, that is truly genius, would really love to see them !
well, because i've received countless emails inquiring how this project turned out, here's the update. we decided that the steel deck was only minimally structural and that it's primary reason for being there was to provide a form for the concrete. we thus decided that it was more important to keep anymore water from getting at the deck, rusting through, and leaking onto our basement floors than it was to actually replace the deck.
thus we had the contractor remove an inch of concrete, fill any major cracks (sometimes using steel rods to close the crack first), replace the concrete, and use a waterproof seal top coat. the rusted decking underneath we kept in place and will decide later if it is worth replacing for cosmetic reasons.
the contractor was a pain in the ass. he added a grit finish to the sealant which wasn't listed in the scope of work. he claims it will make the surface less slick, but more likely i see it collecting dirt and being a maintenance nightmare (which has played itself out to be true). he also left the job site a mess with dust on all of our windows, streaks of concrete on our walls, and a very sloppy edge at the bottom of the sealant. he was only minimally responsive to our complaints. makes me wonder if most contractors truly care about the quality of their work or if they just want to get out of there as quick as possible to make every last red cent on a job regardless of quality. we're using/have used a different contractor for additional concrete/masonry work.
did you do anything to the steel decking that was beginning to rust?
we did a test on my unit where we cut a sheet of decking that almost matched the profile of the existing decking (we could not find an exact match because the townhouses were constructed in 1957). we anchor bolted the new deck on top of the rusted portion of the existing deck and filled the gaps between the two decks with sealant. then repainted the area.
we believe it really is just a cosmetic fix (the new waterproof top coat is what's keeping the water out), so we're holding off on the expense of doing this to additional units.
how bad is the rust, btw? did you ever get a price for your original idea of welding a patch of steel decking underneath the existing? if so, $?
low bid?
my boss and i use to go to job sites about an hour before the scheduled contractor gets there so we can cover things up with plastic...i guess the lesson is never trust those guys to keep it clean.
or thats what happens when you hire the guy who's 20% lower than everyone else
no, it was actually a slightly higher bid, but we went with them based on reputation. i was surprised, but i think it reflects more on the guy who was in charge of this particular job than the company itself. we're still taking bids from them, but as long as this guy's in charge, i will have serious reservations about doing anything with them again.
we had some brick work done by a lesser known competing firm that did a beautiful job replacing portions of brick wall and a limestone coping. you really have to know your area well to find the best people.
I've only managed to find homeless people in my area well.
Sorry I joined the thread late..welcome to the thankless world of providing free time and service to your Condo/Co-op board. I gave up on mine. Glad to hear that things are working out, sort of.
ha, so true, poczatek, so true. i took over for an architect who had been doing this for about 5 years, older guy, experienced architect. at the annual board meeting, he announces that he's stepping down, but says he has the perfect replacement in mind and turns to me. i'm thinking, "oh, what an honor and such great experience for a young architect." little did i know all the unpaid hassles i had in store, but it has been generally a good experience.
...what did it for me was inevitable criticism and mixed bag of bad taste from the peanut gallery who would apparently rather be wallowing in mud than in the environment you will try so hard to improve for them. My building was a modern gem when built, and now is the eyesore of the neighborhood (a very wealthy neighborhood) after 40 years of mismanagement and systemic slum-lording by the former board/owners -Thankless Pigs! Anything we (reform board) tried to do was cutting into their rental profits. Made a couple of friends throughout the process with similar ambitions, so all was not lost.
Poz - same story in mine - we've been trying to replace the windows every year. It would have been 10k avg. per unit 4 yrs ago with building financing at great rate. Consistantly these slum lords who own whole chunks and live in Florida vote no. It drives down sales prices, drives out owner occupants, and is terrible for heating / cooling. They asked me twice to join the board I said no frigg'n way.
Poz - your buildings still pretty nice compared to others in the area. Just look at mine. I swear some bigtime developers gonna have it condemed and grab the land while these old people and slum lords squabble.
Oh - the latest revised pricing for windows is 17K per unit at higher rates
The most important thing for these Floridan Owner/Slumlords is keeping the Assessments Low. Some fucking idiot on our board (20 years ago) motioned to make windows each unit owners' responsibility (all in favor), so they have been intermittently replaced over the past 20 years in only about 30% of the units...completely hodgepodge. And like yours, the price to replace them has gone up considerably (about 15K per unit) I argued about the heat loss (70% of building is single pane steel sash painted shut) I tried to educate them on principle of make up air (carpeting and/or has sealed undercut doors) and so on...they just don't get it or care. I'm done!
well if our last proxy in October doesnt pass we'll be making windows each units responsibility. It adds 20% to cost per unit and will look like ass. Its a big $ hit to the windows, but the building finacing is better than anyone person could get, its a couple hundred a month extra for 5 years plus a down payment. I figured what i could rent it for and I'd still be positive 1-200 a month. Which means these pigs who've been paid off or have mortages from the early 80's are prob making $500 a month or more profit. If there was a way to limit absentee landlord vote share I think we could get it passed. I heard were 4 votes short.
As for low bidders - they low bid masonry wall 18'x100' on the alley in 1993. We just redid it all for 300K last year. Again low bid. So in 2020 we'll prob be doing it again. Assholes.
our coop recently replaced all of our single pane windows with double pane - about 40 townhouses of floor-to-ceiling glass. our monthly cooperative fees are very high ($750/month), but it does allow us to do necessary maintenance and upgrades.
cooperatives are absolutely impossible to maintain, particularly when the property is historically significant. when i think of all the stupid "improvements" that people have done to their townhouses, it makes me a little sick, but at the same time, you can't (and probably shouldn't) have too much say about others' taste or lifestyle unless it profoundly alters the integrity of the building itself.
what was the cost for all the slabs? All 40 thouses?
the stoops are shared between two units. we had a total of 10 done (about half the units), total $40k.
that 40k may have included a couple of ramps we had put in as well. i can't remember the exact breakdown, but thereabouts.
usually if you see the rust in the bottom of the decking...it's 10x worse in the areas between the decking and the concrete........
take a screw driver and start poking around areas such as corners and overlaps and bolt areas.........
take care
b
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