Connecting Wood Floor Joists To Concrete Block Structure In Century Home.

bob_cntrctr

Gentlemen,

Working on a century old house with a concrete block structure. Following another member's helpful tip, I opened the ceiling to check out how the second floor joists are supported at the exterior walls. As is typical, they sit in pockets in the masonry. No positive anchoring, just sitting in there. There is no interior framing either on the inside of the block.

I intend to frame walls against the block, so I'll snug the headers up against the joists and attach them them. But I think it would be best to also connect all that to the concrete block.

I believe they are hollow concrete blocks, but they may have been filled - I'll find out.

What would masons suggest for making the attachment?

Thanks.

Tscarborough

I would suggest you don't. CMU and wood have different thermal characteristics. Unless you are in an earthquake zone, of course.

As an aside, the chance of it being 100 years old and constructed of concrete block are slim. Can you take pictures?

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neolitic

A little "back story" for you Scarborough.
http://www.contractortalk.com/showth...6821#post36682
Good luck.

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(Sorry....it seems there really are dumb questions)

big steve

If you are really concerned, try using a simpson rafter tie/huricane clip from the c/j to the new top wall plate and shoot a corner clip between studs and block. Just an idea to think about good luck.

TimelessQuality

I'd say barn board is the only way to go...just to beef it up a little...

Don't they allow cameras into century old concrete block structure homes??

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"The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." ~ Albert Einstein

A W Smith

Bob any new walls you will be placing under those joists will shrink, The concrete block wall that the joists are resting on however will not.

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Al Smith
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bob_cntrctr

Deed says year built = 1915. Close enough for horseshoes.

Thermal - good point. But there's already wood pinned to the block - from the floor of the basement to the roof and all the way around - if you can believe it. And it's been there since, well, 1915. So I'm thinking thermal mismatch might not be a first-order effect.

What got me on this was this helpful post from another thread:

And it utrns out that's pretty much the situation I discovered - joists just sitting in pockets. Now, the poster was referring to stone structures, but it will to some degree be applicable here......Or maybe the masons will point out that this is exactly as it should be because concrete block will not move like stone.

As for pics - sorry - that'd require a digital camera, which I aint got.

Neo - it must have been nice to have been born knowing everything and never having to ask questions. Did your kids grow up being belittled every time they undertook something they weren't an expert in and had to ask?

bob_cntrctr

Al - thanks for the reply. You might notice I quoted you in the post just above - about joists sitting loose in pockets in stone walls. Sounded like something to look into. So, ya, that's my case. But I thought you were inferring that the remedy was to arrange to NOT have the joists just loose in the pockets any more.

A W Smith

No I was inferring earlier not to disturb the joists and lessen the friction on three sides. if the building was built correctly in its day the joist will have what is called a fire cut. that is, The top of the joist will end at the interior wall surface. If there is a fire and the joists collapse the walls wont be brought down upon the firefighters or surviving occupants from the leverage uplift in those pockets. you will need to consult with an engineer to determine the best way to anchor the joists to the existing masonry wall. Probably by using Simpson hardware anchored to both the block and the joists without compromising the integrity of one or both. While at the same time allowing the joists to pivot out in case or a fire.

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TimelessQuality

Good advice Al!

I have an engineering degree and some ideas for the solution, BUT I would not begin to speculate or even put them out on the internet without an inspection of your particular situation. Way too many variables my friend.

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-Steve

"The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." ~ Albert Einstein

bob_cntrctr

Thanks for this info, guys.

Listen, I'm understanding that this sort of thing makes guys squirm on here. But this house is the way it is, and there are just two possibilities - all the obvious mistakes are just going to stay the way they are, or I'm going to at least make some small improvements within the limits of the reasonable without completely re-engineering the house.

I also understand that you have no idea who you're talking to. A half-way sensible person who'll stop and think before acting, or a half-wit who'll do whatever.

I don't usually like to talk about myself, but following TQ's lead in telling us about his engineering background, here's mine: I have degrees in physics, computer science and business. I held jobs titled "industrial engineer" for 15 years, designing, building, programming, testing and commissioning industrial equipment and manufacturing processes. I was generally assigned to solve problems teams of other people had failed to solve, not becuase I was any smarter, but because I wasn't afraid to ask lots of stupid questions until I was confident I had the right answer. I'm sure lots of line operators joked about this clueless engineer who appeared to have to ask them about how this or that worked in real life. The last big machine I designed was a steam powered lathe. I grew up on a farm. Cleared fields of forests when I was 14, built my first greenhouse at 15, poured a concrete patio at 16. It's decades and decades later and both are still standing. A decade ago I tired of corporate life and went into re-habilitating old properties. Gut them down to the frame and re-build. Do almost all the work myself and have seen some crazy things that need correcting. Because I work alone, I'm missing some industry terminology. I tend to grossly over-build. You can literally park a car on the deck I built at one property last summer. I could go on, but hopefully you get the picture. I'm not going to just do the first stupid thing that comes to mind.

This is information gathering and learning. And I really appreciate you taking the time to inform me. But rest assured, you're not talking to a half wit who'll just launch into a dumb application of your words.

So first thing, I went and checked the joist ends. Of course - no fire cut. Square ends. They protrude ~4" into the block. Another way to get the 'fire cut' effect would have been pockets tall enough that the sqaure end could rotate out. But there's 1/8"~1/4" space between joist and concrete all the way around - left side, right side, top and joist-end.

So once again, here I am - I could just close it back up and leave it like that, or maybe there's some small thing that can be done to at least improve the situation....

Just like the now infamous beam thread. Same house, same joists - discovered that the "beam" holding up these joists in the middle of the house: (a) was just two 2x8's, not laminated; (b) not attached to any joists; (c) was held up at either end by 2x6 posts which were just resting on the floor; (d) the resting points of these posts were a foot off the main basement beam so the load was being transferred to first floor joists; (e) the 'east' joist was cantilevered over the beam and the 'west' joist hanging from the end of it, just nailed to the 'east' joist; (f) happy coincidence, the overlap of the east and west joists was directly over the main basement beam.. So, small, sensible improvement: Open the floor to expose the basement beam; build a new beam of five 2x10's, laminated, glued and screwed; install it a foot to the east so that both east and west joists sit on it and so that the support posts sit on the basement beam directly over the basement posts; attachment to all joists; use steel jackposts. In other words, all I did was move the beam one foot to the east to a better location, and improve how it was built. Or I could have just closed it back up and left that mess another century...

A W Smith

Bob,

why are you so resistant to just making a phone call? Would you call a plumber to do plumbing? Would you call an electrician to to electrical work? Would you try to pave an asphalt driveway yourself or call a paving contractor? There is no fear or embarrassment in calling an engineer. For what they do they are quite affordable. Probably the single most important point is using an engineer releases you from Liability. You are insured right? You told us that your inspection revealed no fire cuts. So lets take this scenario further. You do a seemingly harmless modification to this connection and a few years down the line they have a fire and the exterior walls collapse on the occupants and someone is hurt crippled or killed. Guess what? Your subpoenaed to court for Liability and wrongful death or injury and you have no documentation to protect yourself. Even though what you did had no effect on the collapse you were the last to lay your hands on that connection. The burden of proof is now on you to prove your innocence.

Just pick up the phone, Call a local engineer and when you hang up you will take the burden off your shoulders. Your not asking him to re-engineer an entire house. Just a joint detail upgrade. Just for my curiosity do it now and get back to me with what he says. Think of it as just hiring another subcontractor.

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bob_cntrctr

Ya, it sounds very reasonable.

Special situation: The local town council and building department are on a witch hunt lately, stretching the letter of the law to impose horrendous upgrades in an area of older homes. A house just down the street - when the husband passed on and the property passed into his widow's name, they used that as an excuse to require upgrades on century-old out-buildings that didn't meet current zoning and an entire new septic system and well. Cost her $30k by the time it was all done, which was 1/3 of her husband's estate. For an administrative name change. So the whole community is on strike regarding getting permits for anything in protest. So what's that got to do with an engineer? Just like you guys asking for pictures, an engineer is going to say "I'll come out to have a look.", which means a local engineer. Small town, few options, odds are high your local engineer is someone's cousin at city hall. A mention to ol' cous', and it'll be 'you gotta move that garage', and '$3k fine for the house being too close to the road', and new septic, and move the well, and..... no way. This is what happens when the state becomes oppressive. But don't get me started on politics....

That said, same thing could apply to new kitchen cabinets. Hang 'em wrong, someone loads it up with china, falls on their head...

Anyway - Sometimes the correct conclusion is to do nothing because of too many constraints. And this is starting to sound like that. In absence of any new bright ideas, think I'll just frame my new wall under the joists so I can insulate and not touch the rest. I'll probably connect the newly framed wall to the barn board and leave it at that.