Author Topic: Stupid Idea of the week: Replacing Rafters With Trusses  (Read 1162 times)

Jon Bon

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Stupid Idea of the week: Replacing Rafters With Trusses
« on: October 09, 2017, 04:52:13 PM »
So I live in a smaller 2 story house, my spouse and I had talked about adding on, as sharing the bathroom with all the kids would eventually get old. Our plan was for a small 2 story addition to the back of the house. I met with a builder and promptly did a spit take: between 150-250 THOUSAND dollars. Now mind you I only paid $225k for the house and the land is probably worth 150k alone.

Recently I have become mildly obsessed with roof trusses. They hold so much weight, and are so small, and (relatively) cheap!

So here is my crazy ass plan I have a 24x24 2 story house. Would it be completely bat shit crazy to tear off my existing stick framed rafters and replace them with 12/12 trusses with an attic room? Back of the napkin math would give me a room that is 12x24 feet, which would be plenty huge for a bed, bath, and office.

The roof needs to be replaced in the next 5 years and it would obviously save us money on not digging a new foundation. For arguments sake assume there are no engineering issues and the home can support the extra weight.

Anyone done anything like this? Is this a completely stupid plan or a somewhat cost effective way to gain extra space? I'd appreciate any feedback!

Paging Mr. Paddedhat!

Papa bear

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #1 on: October 09, 2017, 05:10:33 PM »
Sometimes, just sometimes, I think you may be crazier than me. 

I'll ask it. Does your local city allow for new construction living space on the 3rd floor?  Are you zoned for that?


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Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #2 on: October 09, 2017, 05:14:47 PM »
Sometimes, just sometimes, I think you may be crazier than me. 

I'll ask it. Does your local city allow for new construction living space on the 3rd floor?  Are you zoned for that?


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I mean I did phrase it "Stupid idea of the week" :-)

Well there was a new home just completed in the last 18 months or so with a 3rd floor suite. I assume they allow it to keep the houses footprint smaller on the smaller lots.

So lets just say city approval achievable.

Maybe the theme of this is "Just because you can do something does not mean that you should?"

Lulee

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #3 on: October 09, 2017, 05:41:21 PM »
Looking forward to PaddedHat and other wise folks responses.  My mind wonders though, is there any way to see if the foundation system can support another level of living space?  And does having a new profile to the outside do anything to the building's ability to withstand high winds and tornados?  Cost-wise, would a reconfiguration of existing space be cheaper?

terran

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #4 on: October 09, 2017, 09:25:10 PM »
Is there a particular truss design that you're looking at that would allow this? Trusses usually have webbing throughout which is what gives them their high strength with little material. If you want useable space "inside" the roof you're usually better off with rafters as there's no webbing to get in the way.

Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #5 on: October 10, 2017, 05:07:04 AM »
Is there a particular truss design that you're looking at that would allow this? Trusses usually have webbing throughout which is what gives them their high strength with little material. If you want useable space "inside" the roof you're usually better off with rafters as there's no webbing to get in the way.

They make ones like this for exactly the application I am discussing. Stick framing is actually much weaker, requires more collar ties (thus reducing your interior space), and takes much longer. The advantage is it is a much cheaper option.

Ok so I was thinking more, here are a few ideas.


Pro:
1. Structural - probably going to be stronger then existing stick framing. House is already a box, this would just be a strong triangle sitting on top of a strong box?
2. Structural - Light trusses at 24 on center (with a higher slope) would probably be lighter then existing rafters 16 on center. This might somewhat compensate for additional weight of roofing?
3. Disruption - Would not require the ceiling in the second floor to be removed? Trusses are their own independent system. Existing second floor attic joists could remain. If I can live in the house while the roof is removed and replaced I might actually think about doing this.
4. Time - Really reduces the amount of time a house is open to the elements. In theory you could build the entire roof at the warehouse, put it on a truck and fly it in with a crane. (Probably not going to happen, just saying)

Cons:
1. Cost - trusses are more expensive (offset by reduced labor)
2. The root of this idea is really stupid?


« Last Edit: October 10, 2017, 05:15:59 AM by Jon Bon »

Agg97

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #6 on: October 10, 2017, 07:44:23 AM »
The first thing to figure out is how to beef up your structure to support live loads on the 3rd floor.  You'll need a structural engineer for this...the swap from rafters to trusses is one thing; making the 3rd floor occupiable by increasing the load on your framing is another altogether.  Potentially, the structure will need to be supplemented all the way down to your foundation.  I've seen adding just a room to a previous attic space run about $60k.  If you're talking the whole floor, it's most likely well north of 100k. 

ncornilsen

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #7 on: October 10, 2017, 08:04:06 AM »
1. Competitive bids. that price is crazy it seems. You could tear down and rebuild for that I think!

2. I must echo that adding a third floor will possibly require foundation upgrades, wider footers, more sill plate bolts,  increases in shear strength of walls, etc.


Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #8 on: October 10, 2017, 08:38:12 AM »
1. Competitive bids. that price is crazy it seems. You could tear down and rebuild for that I think!

2. I must echo that adding a third floor will possibly require foundation upgrades, wider footers, more sill plate bolts,  increases in shear strength of walls, etc.

1. Yes I would never pay that. I honestly wanted to get just the shell put on but they said they wont do that. I live in a fancy neighborhood, so they probably assumed I am spendypants and not MMMian

2. Definitely possible. The house is 100 years old, so I assume that it is well overbuilt and could handle the load? Obviously I would talk to an engineer about it, as it would be required for permits. I guess I like the idea of going up because it would be less disruptive? I mean I could have the attic shell put on with petty much no interior construction? Adding onto the back of the house would be a nightmare.


lthenderson

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #9 on: October 10, 2017, 09:11:12 AM »
I've never done anything like this but I'm sure it is possible to do. You are opening up a lot of risk during the time you start dismantling your existing roof to the time you get the new roof on and weather tight. Not only are you open to weather events like rain but also high winds.

There is also a lot more costs involve than you are probably thinking. There is loads of wiring in ceilings that will have to be dealt with along with other protrusions like vent stacks, etc. Many systems are designed to move air only so far so adding another story may mean you have to resize other parts of your mechanicals. You will either need to remove the old upstairs ceiling or will have to support it from below until the new trusses are in place and the bottom chord of your stick built roof sistered to the new trusses for support. Sistering new trusses to old ceiling joists is problematic as there are usually a lot of obstacles like electrical outlets, wires, etc that you have to work around. You will need to add chases (and obvious stuff like stairs) in your existing upper floor to allow for HVAC, plumbing, electrical concerns to the new usable space. All these can be addressed but they aren't always simple and they do add money to a project like this.

If the addition of 288 square feet is something that has to be done to a house to make it livable for you, it is probably more efficient to either trade houses or utilize the existing spaces in a more efficient manner.

hoosier

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #10 on: October 10, 2017, 01:50:21 PM »
What is your current roof pitch?

Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #11 on: October 10, 2017, 03:57:33 PM »
What is your current roof pitch?

8/12?

Its steep enough that I can't really walk on it, and low enough that its maybe 7 feet high at the apex when I am standing in the attic.

ncornilsen

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #12 on: October 10, 2017, 09:57:50 PM »
1. Competitive bids. that price is crazy it seems. You could tear down and rebuild for that I think!

2. I must echo that adding a third floor will possibly require foundation upgrades, wider footers, more sill plate bolts,  increases in shear strength of walls, etc.

1. Yes I would never pay that. I honestly wanted to get just the shell put on but they said they wont do that. I live in a fancy neighborhood, so they probably assumed I am spendypants and not MMMian

2. Definitely possible. The house is 100 years old, so I assume that it is well overbuilt and could handle the load? Obviously I would talk to an engineer about it, as it would be required for permits. I guess I like the idea of going up because it would be less disruptive? I mean I could have the attic shell put on with petty much no interior construction? Adding onto the back of the house would be a nightmare.

I added on the back of my house, and it wasn't too bad. I would not assume a 100 year old house has an overbuilt foundation... at that age you're lucky if it has one that's more than piles of rocks!  In my 60 year old house, I'm not sure the stem wall has rebar, and the framing definitely wasn't bolted to it.

paddedhat

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #13 on: October 11, 2017, 06:09:51 AM »
It's not a common move, but far from unheard of.  Typically what I see, here in the mid-Atlantic region, are ranch style homes that are converted to Cape Cods.  The process typically involves a framing contractor, a large crew, a large tarp, and a 4-5 day window of theoretically decent weather.

Now for the potential issues. Oddly enough, trusses are not the best option here. The reasons are many, but I'll cover the big ones. First, typically there is a major attempt made to save the ceiling structure and finishes, of the rooms below. This is accomplished by prepping the house to accept new floor joists and rafters. First attic insulation, HVAC, electrical wiring, plumbing, etc.. is removed. Next the roof shingles, roof deck (plywood, or board sheathing) and rafters are removed. The first step in reconstruction is to install new floor joists. In your case these would probably be 2x10s. They are cut to length, then air nailed to the sides of the existing ceiling joists. New plywood decking is installed over the floor joists. Now you have a third floor, and did little to no damage the the existing second floor ceilings. Next, rafters are cut and installed. At that point the whole job for the framing and roofing crew is no different that a new home. You will have a roughly 12' X 24' interior room with 5' knee walls on the long walls.

As you can see, trusses would be more applicable to a new construction situation. By stick framing you are able to adjust for all kinds of obstacles that arise in these kinds of situations.  Trusses are computer designed, and built on huge jigs, so that they are all exactly alike. Thus, an engineered product built to high standards. A hundred year old house can be quite the opposite. One potential disaster that comes to mind would be a high center bearing wall. Unless you have a real unicorn, a hundred year old, stick framed house typically has interior bearing walls and short ceiling and floor joists spanning from the outside walls to the interior bearing wall, which is typically located dead center of the structure, and running parallel with the front and back walls of the structure. If that wall ended up at a slightly higher elevation from any point on the front or back wall of the home, you would have a pretty big issue for a truss install. Trusses are typically designed for two bearing points and a free span between them. So it is designed to bear on the front and back walls and now it's "rocking" on the center wall, and you have a big engineering problem, since you bearing is in the middle and not where it should be. If this were to happen on stick framed renovation, it means there is a nearly undetectable lump in the middle of the new floor, that doesn't impact a thing. The same is true for a lot of conditions you might find in a century old home. For example the roof is now off, and your carpenters start "pulling tapes" to see how square and straight the existing structure is. Turns out it's 2" out of square, and the front wall is 1-1/2" shorter than the back. No big issue with stick framing, but a huge headache with the factory made trusses piled up in the yard. A good framing carpenter, doing a stick frame roof in this situation, is a lot like a skilled custom dress maker. He can tuck, twist and massage the new roof to make it fit. There are a few other reasons that I avoid trusses, in general, but I doubt that anybody doing the job for you would gravitate toward them, so I'll save all that.

 Now, it on to killing an old wive's tale. Sorry, but there is zero reason to believe that ANY hundred year old building is.

A. Extremely well built, since "that's how they built them, back in the day".
B. A tired old POS that will fall over in the next wind. 

The truth almost always lies somewhere in the middle ground. Anything more than 50 years old, or so, in the states, is a total wild card. It could be ridiculously overbuild, and capable of lasting for a few more centuries, or slap together by a bunch of farmers, on nights and weekends, with the dual goal of, "getting it done, it's getting cold soon", and "stop thinking 'bout all that fancy store bought material, there are plenty of good nails in that milk can, out in the shop. Use what you can, and spend some time straighten the bent ones, fer Christ sake stop whining, you think we got city money, Elwood?"  Seriously, before codes, and building standards there was some really crazy shit out there. Chances are, 99% of 100 year old structures that are straight and sound can handle a fairly light attic reframing, but it's best to assume nothing.

Finally, don't forget, you need a staircase to the new room. It can be tough to find the space for one on the second floor of a small home,  without losing some serious real estate in a bedroom, or at least  creating some "interesting" traffic flow. As for the concept overall, I'm not a big fan, and would only do it, if you have no room to do a typical addition. The $150-250 number is bat shit crazy.  In a rationally priced market, there is no reason that $60-80K shouldn't give you a simple two story addition.
« Last Edit: October 11, 2017, 06:13:40 AM by paddedhat »

Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #14 on: October 11, 2017, 07:22:33 AM »

"fer Christ sake stop whining, you think we got city money, Elwood?" 



"This is gold Jerry GOLD!"

Thanks Paddedhat.  So it sounds like a 3rd story would be every bit as disruptive as an addition off the back would be. The part about trusses versus stick framing makes a ton of sense when you stop to think about it. None of the work sounds especially complicated, but probably would be harder then an addition off the back and much more limited in space/working conditions. 

I feel like you should start a MMM consulting business, We pay for your plane ticket and hotel room and you get to spend a weekend in whatever city that the Mustacheian lives in.

Well I think this about concludes this weeks episode of Stupid Idea of the Week!


paddedhat

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #15 on: October 11, 2017, 08:14:05 AM »
So it sounds like a 3rd story would be every bit as disruptive as an addition off the back would be.

When it come's to my  1-10 scale of,  "this remodeling is really like living in hell, when will it end?"  I would put it like this.

 A #1 rated event is when you're at work when the plumber shows up. He changes the toilet, walks the dog, leave a very reasonable bill on the kitchen island, with a few mints on top, doesn't leave a single shred of evidence (absent the new toilet) that he was ever there, and is gone before you get home. Like the existence of the snuffleupagus, this is obviously a fantasy.

 A #10 is. You are squatting in your garage, you have a mini-fridge, a portable camping toilet and a microwave. It's been six months now. Your broke, and now know exactly what "Two weeks" and, "we ran into a problem we didn't anticipate" means. The house looks like a post Katrina photo shoot. Your contractor was just hauled away by the DEA, since he had a 1/4 kilo of blow in his truck. You then learn, from the humorless, cheap suit and crew cut wearing hard-assed investigator, that all the shady contractor's "helpers" who endlessly cycle through your home are what he likes to call "customers", and wants to know how much of a cut you get out of all this. The building inspector is standing behind the nice DEA agent with that, "I'm not happy" look. You just found out that a "helper" accidentally left your cat out, and the neighbors are circulating a petition to encourage you to get your shit together.

Keeping that in mind, a roof build out is going to be quick, yet far from painless, so I would give it a 7-8. A thoughtful contractor doing a two story addition, had the ability to keep you and your daily life fairly well separated from all the mess and drama. If it's well done, an simple addition should be somewhere in the 3-4 range.

Bourbon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #16 on: October 11, 2017, 08:23:54 AM »
I should probably get my own thread for this, but my stupid idea in my 116 year old house for some time was to dig out a room in the basement.  Most of the home is on a narrow crawlspace, with a solid stone block foundation.  The back of the house has a 10x24ish cellar underneath it.  Originally it had an access to the outside, but that porch was covered over and incorporated into the house, so now I access the cellar via a trap door in the laundry.

Anyway, always wanted a basement, and I have about 7 feet of clearance down there.  If I could just dig it out by hand over the course of many bucketloads of dirt, then I could somehow pour a concrete floor and finally have the basement I've always wanted.   

Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #17 on: October 11, 2017, 08:30:44 AM »
So it sounds like a 3rd story would be every bit as disruptive as an addition off the back would be.

When it come's to my  1-10 scale of,  "this remodeling is really like living in hell, when will it end?"  I would put it like this.

 A #1 rated event is when you're at work when the plumber shows up. He changes the toilet, walks the dog, leave a very reasonable bill on the kitchen island, with a few mints on top, doesn't leave a single shred of evidence (absent the new toilet) that he was ever there, and is gone before you get home. Like the existence of the snuffleupagus, this is obviously a fantasy.

 A #10 is. You are squatting in your garage, you have a mini-fridge, a portable camping toilet and a microwave. It's been six months now. Your broke, and now know exactly what "Two weeks" and, "we ran into a problem we didn't anticipate" means. The house looks like a post Katrina photo shoot. Your contractor was just hauled away by the DEA, since he had a 1/4 kilo of blow in his truck. You then learn, from the humorless, cheap suit and crew cut wearing hard-assed investigator, that all the shady contractor's "helpers" who endlessly cycle through your home are what he likes to call "customers", and wants to know how much of a cut you get out of all this. The building inspector is standing behind the nice DEA agent with that, "I'm not happy" look. You just found out that a "helper" accidentally left your cat out, and the neighbors are circulating a petition to encourage you to get your shit together.

Keeping that in mind, a roof build out is going to be quick, yet far from painless, so I would give it a 7-8. A thoughtful contractor doing a two story addition, had the ability to keep you and your daily life fairly well separated from all the mess and drama. If it's well done, an simple addition should be somewhere in the 3-4 range.

I guess my scale is somewhere along the lines of: 4 -  take a week at the inlaws house to stay away from the worst of it, and a 10 -  sign a 3 month lease in an apartment because your house is post Katrina.


Jon Bon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #18 on: October 11, 2017, 08:31:46 AM »
I should probably get my own thread for this, but my stupid idea in my 116 year old house for some time was to dig out a room in the basement.  Most of the home is on a narrow crawlspace, with a solid stone block foundation.  The back of the house has a 10x24ish cellar underneath it.  Originally it had an access to the outside, but that porch was covered over and incorporated into the house, so now I access the cellar via a trap door in the laundry.

Anyway, always wanted a basement, and I have about 7 feet of clearance down there.  If I could just dig it out by hand over the course of many bucketloads of dirt, then I could somehow pour a concrete floor and finally have the basement I've always wanted.

He could have is own category: "Paddedhat tells homeowners they are stupid"

Would at least make for some good reading!


paddedhat

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #19 on: October 11, 2017, 09:16:09 AM »
I should probably get my own thread for this, but my stupid idea in my 116 year old house for some time was to dig out a room in the basement.  Most of the home is on a narrow crawlspace, with a solid stone block foundation.  The back of the house has a 10x24ish cellar underneath it.  Originally it had an access to the outside, but that porch was covered over and incorporated into the house, so now I access the cellar via a trap door in the laundry.

Anyway, always wanted a basement, and I have about 7 feet of clearance down there.  If I could just dig it out by hand over the course of many bucketloads of dirt, then I could somehow pour a concrete floor and finally have the basement I've always wanted.

He could have is own category: "Paddedhat tells homeowners they are stupid"

Would at least make for some good reading!

Hey now, were dancing might close to insulting the family, when it comes to denigrating this fine idea. Seems that a century ago, the industrial age was going full speed and the northern parts of the good ole' USA had a major shortage of housing. A lot of cities and towns got big, fast, and most of it was working class housing.  Since this stuff had to be affordable, it was often crammed into row homes, double homes, and similar. Often, one corner to cut was to make the basement 6-7 feet tall. Now, it didn't take long for a lack of birth control and Netflix to result in Joe and Mary, coal miner and shirt factory seamstress, respectively, to end up with a ton of spawn. Room was at a premium and the yard was the size of a bedspread, so there weren't going to be any fancy additions. As a result, if your from old Euro stock, from an old working class area, you probably have relatives that have a story to tell about diggin' the basement by hand. My Polish grandfather did it. He made truck frames for a living, and spent months of his free time carefully digging his basement another foot deep. All by hand, buckets of dirt loaded into the family sedan and dropped off at a farm somewhere. In the end he ended up with a laundry room, full bath, "rec" room and little workshop. All as a result of digging, and hauling about 600 cubic feet of dirt out, hand carried in buckets, up the outside cellar steps. This works out to roughly 1.3 full sized tri-axle dump trucks worth. Guarantee if you stop at a dive bar in a working class city, anywhere in the Mid-Atlantic, mid-west, or New England, and say, "Any of you old farts ever hear of digging a basement floor a foot or two deeper with nothing but a shovel and a coal bucket" you will get an evening full of stories.

Bourbon

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #20 on: October 11, 2017, 09:20:31 AM »
I should probably get my own thread for this, but my stupid idea in my 116 year old house for some time was to dig out a room in the basement.  Most of the home is on a narrow crawlspace, with a solid stone block foundation.  The back of the house has a 10x24ish cellar underneath it.  Originally it had an access to the outside, but that porch was covered over and incorporated into the house, so now I access the cellar via a trap door in the laundry.

Anyway, always wanted a basement, and I have about 7 feet of clearance down there.  If I could just dig it out by hand over the course of many bucketloads of dirt, then I could somehow pour a concrete floor and finally have the basement I've always wanted.

He could have is own category: "Paddedhat tells homeowners they are stupid"

Would at least make for some good reading!

Hey now, were dancing might close to insulting the family, when it comes to denigrating this fine idea. Seems that a century ago, the industrial age was going full speed and the northern parts of the good ole' USA had a major shortage of housing. A lot of cities and towns got big, fast, and most of it was working class housing.  Since this stuff had to be affordable, it was often crammed into row homes, double homes, and similar. Often, one corner to cut was to make the basement 6-7 feet tall. Now, it didn't take long for a lack of birth control and Netflix to result in Joe and Mary, coal miner and shirt factory seamstress, respectively, to end up with a ton of spawn. Room was at a premium and the yard was the size of a bedspread, so there weren't going to be any fancy additions. As a result, if your from old Euro stock, from an old working class area, you probably have relatives that have a story to tell about diggin' the basement by hand. My Polish grandfather did it. He made truck frames for a living, and spent months of his free time carefully digging his basement another foot deep. All by hand, buckets of dirt loaded into the family sedan and dropped off at a farm somewhere. In the end he ended up with a laundry room, full bath, "rec" room and little workshop. All as a result of digging, and hauling about 600 cubic feet of dirt out, hand carried in buckets, up the outside cellar steps. This works out to roughly 1.3 full sized tri-axle dump trucks worth. Guarantee if you stop at a dive bar in a working class city, anywhere in the Mid-Atlantic, mid-west, or New England, and say, "Any of you old farts ever hear of digging a basement floor a foot or two deeper with nothing but a shovel and a coal bucket" you will get an evening full of stories.

So you're saying I don't need to consult a structural engineer, I can just start digging?!!!!!!!

What am I putting under the concrete I pour?  I still need to figure out  a stairwell to get down there.  I regraded and landscaped the back yard last year, so unfortunately I can't get a concrete truck back there, but I could rig up some tubing and get a dozen guys running wheelbarrows.


paddedhat

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #21 on: October 11, 2017, 05:03:12 PM »

So you're saying I don't need to consult a structural engineer, I can just start digging?!!!!!!!

What am I putting under the concrete I pour?  I still need to figure out  a stairwell to get down there.  I regraded and landscaped the back yard last year, so unfortunately I can't get a concrete truck back there, but I could rig up some tubing and get a dozen guys running wheelbarrows.

Nope, not saying it's smart, a good idea, or should be done without qualified council of a professional. I am saying that it's been done a zillion times, using little but common sense and hand tools. So, a few quick questions. How deep is it now, exactly? How deep do you want it to be, with a finished floor? What are the basement walls made of, and in what condition are they? Is there a beam, and/or posts involved? Is there any floor to speak of now, gravel, thin cracked concrete, or whatever? Is the space damp, wet or prone to flooding? Is it going to be easy to dig, or not?

trollwithamustache

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #22 on: October 11, 2017, 05:29:58 PM »
At least in my state, a  third story on a wood frame building  requires the blessing and stamp of an engineer.   Unfortunately, making the attic habitable would probably count as a third story.

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #23 on: October 12, 2017, 06:39:28 AM »

So you're saying I don't need to consult a structural engineer, I can just start digging?!!!!!!!

What am I putting under the concrete I pour?  I still need to figure out  a stairwell to get down there.  I regraded and landscaped the back yard last year, so unfortunately I can't get a concrete truck back there, but I could rig up some tubing and get a dozen guys running wheelbarrows.

Nope, not saying it's smart, a good idea, or should be done without qualified council of a professional. I am saying that it's been done a zillion times, using little but common sense and hand tools. So, a few quick questions. How deep is it now, exactly? How deep do you want it to be, with a finished floor? What are the basement walls made of, and in what condition are they? Is there a beam, and/or posts involved? Is there any floor to speak of now, gravel, thin cracked concrete, or whatever? Is the space damp, wet or prone to flooding? Is it going to be easy to dig, or not?

Current height is about 6.5'.  Would like 8' finished floor to ceiling.

Walls are rock, exterior walls have been spray foamed over. Rocks are around 3' wide.

Floor is dirt with plastic cover.  Does get damp under the plastic, but no excessive water. Musty smell.  Sump pump has never turned on.  My neighbor has a gutter that needs to be repaired that is likely contributing to the water, but he's on a 5 year fix it timeline.

paddedhat

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #24 on: October 13, 2017, 06:43:00 AM »

Current height is about 6.5'.  Would like 8' finished floor to ceiling.

Walls are rock, exterior walls have been spray foamed over. Rocks are around 3' wide.

Floor is dirt with plastic cover.  Does get damp under the plastic, but no excessive water. Musty smell.  Sump pump has never turned on.  My neighbor has a gutter that needs to be repaired that is likely contributing to the water, but he's on a 5 year fix it timeline.

The massive rock walls add a degree of difficulty to the project. Anything that compromises the stability of the footprint of the wall would be a mess. There are two ways to deal with this. First is distance, second is shoring.

In a distance model you would pick a ratio of depth to distance from the inside face of the wall and excavate to this edge. So, if you are digging  an additional 24", you might stay 24" away from the edge of the wall. This "slope angle" would be highly dependent on existing soil conditions. It may be a foot, or it may be four. I doubt you have a footer in this case, as older over-sized walls in this application were typically started at the visible width, in the bottom of the excavation, without footings. Since old stone walls can be notoriously unstable, this can lead to extreme situations. I have seen full height basement additions added to old farmhouses, where there is an interior block wall of the addition that sits 3-4 feet inside the room, and supports the below grade portion of the old stone wall. So there is this odd space in the basement with a chest high wall, and often a concrete capped "shelf" extending to the existing stone wall. In your case, you might end up with a mini version of this, with a 2' tall "Bench" running around the room.


 The other option is shoring, where you dig straight down, at the edge of the rock wall, and expose a section a few feet wide. This is then supported with shoring, which is a short vertical wall designed to take the load. This work is done by skipping sections, then doubling back to shore the remaining sections. Essentially, half way through a shoring project, the interior perimeter would be a checkerboard of equal spaced sections of shored and undisturbed areas.

None of this is technically complicated, nor is it out of reach for a driven (or half mad?) DIYer.  That said, given the depth you would need for a proper concrete slab and a bed of drainage gravel, a total of 8", and the added height you desire, it's quite a project. It would take competent guidance from either a structural engineer or a contractor who is well versed in this type of work.

Personally, I'm so lazy, just thinking about this one makes me yawn. Good luck.

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Re: Stupid Idea of the week: Replacing Rafters With Trusses
« Reply #25 on: October 16, 2017, 02:27:02 PM »
I can't believe I'm the first one to say this, but... if the house really is too small, then buy a larger house.

More realistically, just cope. I grew up with my parents and sister and only 1 bathroom in the house. Small, single story house.

As someone with a 100 year old house (ok, 98, but close enough), what you're considering is a nightmare. Doesn't matter how well it's built - it's old! Things do wear out over time. Anytime I touch anything, I have to assume that something else will come up. And that's small stuff. You're talking about a major reno. You're more likely to end up with a massive money pit and be stuck with a horrible situation, unable to get out of it.