I have this dream of replacing my 12x24' garage with an 18x24. Since this old property was developed before zoning and codes, the garage is smack on the property line, so demo and new construx could potentially be a headache with the township. My other idea was to add a 6' wide enclosed lean-to on the side and move all the yard stuff out there leaving space for a car/tools/wrenching area in the original structure. Not keen on having two very small spaces and I would rather have one larger space.
So the idea is to beam the side wall and use a couple poles so I can knock out the wall.
But, I gotta do it right. How do I calculate my beam span so I can figure out if this is feasible?
Pic for reference. I would add on to the left side, then a beam to replace the stud wall of the existing structure.
Do you really need it fully open? A six or eight foot span allows access easily, and wouldn't take a horribly big header. There should be readily available charts online to define weights and spans and sizes.
I'd spend more time figuring out how to keep the concrete pads from moving independently and tearing it apart.
I really do want a nearly full span. Even with the garage completely empty there is no room on either side to operate a floor jack. I can turn it at an angle which then blocks the whole walk space. I'm not exactly compact or nimble. Being able to pull in and cheat the car to the left will make enough space on both sides.
The addition would have a post/beam construction more like a deck with poured concrete piers supporting a wood floor. The only things in there would be light stuff like pushmower, motorcycle, and snow blower. The roof would be rafters/purlins with corrugated poly roofing.
It wod be much more feasible to do 5 posts on that wall, every 8' or so. The whole 24' would be open, but you'd have 3 posts down where the wall used to be and one on each corner. 24' is a pretty big ask for a span to take out a load bearing wall.
I did something similar in concept with my garage reno- there was a 20' span that I wanted all open, that had a slant (shed) roof coming off of the header, and even with a pair of 2 x 10 microlams I still had to put a 6x6 post in the middle.
I don't think this is a job for internet engineering. And by the time you pay the engineer (about $3500), a couple posts will seem much more tolerable.
The problem isn't the span. I can do that off a chart for microlams. Yes, you can carry the load with a microlam full span.
The problem is the lateral stability. That exterior wall is also acting as a shear wall, and bracing will be almost non-existant when you remove it.
When a wind load hits the front wall, the side load bearing wall resists it (because of the sheathing/ bracing/ siding). When it's gone, you've got nothing.
If you use a wood truss instead of a beam, you can get free engineering from the truss manufacturer.
If it was mine, I'd add posts every 8' with diagonal bracing at the top.
The problem is that you change the foundation load from being evenly distributed over 25' to 4 point loads carrying the same weight.
The posts should have much larger footings than the current exterior wall has.
BTW, you've still got a footing issue if you replace with a full span beam.
Your load which is currently distributed evenly over 25' of bearing will be changed to 2 point loads at each corner.
Still need bigger footings.
In reply to SV reX :
Excellent points. The sheathing on that wall adds diagonal strength which prevents the wall from moving back and forth. I was also thinking about the load being distributed on the current foundation. For mine, I had 6x6 posts with 18" diameter footings sunk well below the frost line.
Another option..,
Take the whole roof off, add new footings at the new outside wall of your "shed", and replace all the roof rafters with clear span trusses.
I know that sounds like a lot of work, but you may find it is the best option.
Added bonus... make the new trusses scissor trusses, and gain enough ceiling height for a legit lift.
Edit: This could actually be done removing only half of the roof. The right hand half rafters could be secured to the new trusses without removing the roofing. (Assuming the existing rafters centers make sense for the new trusses)
I'm guessing by the age of the existing garage that the roof is not trusses, but probably just rafters and maybe a ridge beam. Any structure spanning over the tops of the walls to prevent them from blowing outward?
We have an older property (original house dates to sometime before the Civil War) and construction techniques were...different. Very much a sort of "well, that seems strong enough" goin on. Granted it's held up for 175 years so I guess they didn't do too badly with that philosophy.
In reply to SV reX :
Exactly where I was going with my question about the current rafters.
I had trusses fabbed custom for another part of my garage, and they were pretty reasonaable- about 100$ each. Of course that was right before lumber doubled in price.
In reply to volvoclearinghouse :
The trusses are cheap. It's the engineering and the foundation.
SV reX said:Another option..,
Take the whole roof off, add new footings at the new outside wall of your "shed", and replace all the roof rafters with clear span trusses.
I know that sounds like a lot of work, but you may find it is the best option.
Added bonus... make the new trusses scissor trusses, and gain enough ceiling height for a legit lift.
Edit: This could actually be done removing only half of the roof. The right hand half rafters could be secured to the new trusses without removing the roofing. (Assuming the existing rafters centers make sense for the new trusses)
This did cross my mind. Trusses aren't hideously expensive. I would probably remove the whole roof since what is up there is questionable at best.
Rafter and stud spacing is eyeball inches on center for the whole thing. Some are 14, others are 24. Someone threw some rough-cut lumber into a stud wall and sheathed it with shiplap.
One of the compelling reasons for going full-bore with this (involving the township, pouring proper concrete, erecting a steel building) is because the garage is sitting on a cinder block foundation of unknown construction. The concrete floor was poured in there as a floating slab before I owned the place. My thought with just adding a lean-to and beam was that I could easily get in and pour a proper foundation on the side where I'm doing the work.
In reply to Curtis73 (Forum Supporter) :
Just a thought, I had a floating concrete floor that someone had poured before I owned the place. I jacked cars on it for years. When I finally redid everything I ripped up the old concrete and discovered it varied from 1 to 2" thick.
Pretty scary.
volvoclearinghouse said:I'm guessing by the age of the existing garage that the roof is not trusses, but probably just rafters and maybe a ridge beam. Any structure spanning over the tops of the walls to prevent them from blowing outward?
We have an older property (original house dates to sometime before the Civil War) and construction techniques were...different. Very much a sort of "well, that seems strong enough" goin on. Granted it's held up for 175 years so I guess they didn't do too badly with that philosophy.
I'll have to double check, but I don't even think there is a ridge beam. I know the house doesn't have a ridge beam, they just leaned the rafters against each other. They're held in place with some scraps of shiplap which I assume they used to hold them there until they put the roof slats on... which, by the way, are just slab-cut pine with live edges.
The house actually began life in the 1800s as a chicken coup. Not kidding. Three additions on the house which look like they were done in the 20s (when the neighborhood was built and they added a kitchen), the 50s (added a mudroom off the kitchen) and the 60s (added a living room). Some of the studs in this house are hand-hewn 3x3s with downy feathers stuck in the fibers. Renovations have been an absolute trip.
This is what I imagine things look like in cross-section but I have no idea.
The gray squares are a cinder block foundation of unknown depth. Brown is dirt, yellow is the poured slab. I was thinking that I could jack up and support the left side under the roof, dig, and add a proper foundation under the left wall.
The whole thing needs a bulldozer, but I'm trying to figure out a way to do this without adding sketchy on top of sketchy.
Find out what the property line setback for a non-attached garage is. Some places it is only 3 feet, especially in an older neighborhood. Is there enough space in the front to move the garage forward? Build a new thickened edge floating slab garage. I had a friend who literally split his garage in two down the ridge line, rolled half of it over on pipes onto a new slab extension, and added new roof bottom and top chord rafter boards. Crazy, but it worked. You could add new trusses and make it much easier.
EDIT: also, what is your garage door's height? Whatever it is, it looks like it's the same as the wall height. If it's 7', than any beam you put in that wall will have to sit on top of the wall. You can also make that wall into a shear wall by adding a 4x8 shear panel at both ends of the wall opening, so you would have a 16' opening between the end walls along with the 24' long LVL beam.
Are you sure it wouldn't be cheaper in the long run to rebuild, instead of engaging in a bunch of turd polishing? Lift it. Throw the roof away. Pour a new proper pad. Cut one side wall away, move it six or eight feet away, fill the holes you've created and put a proper new roof on it.
Streetwiseguy said:Are you sure it wouldn't be cheaper in the long run to rebuild, instead of engaging in a bunch of turd polishing? Lift it. Throw the roof away. Pour a new proper pad. Cut one side wall away, move it six or eight feet away, fill the holes you've created and put a proper new roof on it.
Nothing will be cheaper than adding on a lean-to. That is something me and a couple contractor friends can do in two weekends, $1500 of material, and some pizzas. If I were building new with no structure currently there, I'm probably going to be in the vicinity of $16-20k, (9000 structure, 4000 concrete, 1000 electrical, 750 roll up door, 150 man door, two windows, etc etc) and that doesn't take into consideration the demolition and disposal of the old structure. Not to mention I would have to budget for some means of storing the stuff that currently lives in it. I would just get a HF tarp garage, but the only place I have to put it on my property is in the driveway right in front of where the excavation and concrete equipment would have to have access to it.
I have excavation equipment at my disposal - loader, backhoe... probably all I need. I can likely find a trencher if I want to bury the new electrical service. I can prep for the pour to save a little money there, but trash hauling is not cheap. I can get a permit for the municipal dump and I have a 6 x 16 flatbed trailer, but I would imagine that self-hauling a garage demo one trailer load at a time is going to take weeks.
This is the kind of brain-shaking I need, guys. I'm tired of my projects sitting around, and I'm really tired of taking cars to the shop for dumb stuff like oil changes and brake jobs. $50 for an oil change isn't awful, but it's so frustrating that any time I need a radiator hose I have to debate laying on a driveway (which is usually either blisteringly hot, frozen solid, or soaking wet) or paying someone to do it and waiting for their schedule. My last place had a 40x40x14 steel barn and a 36x48 pole shed. I sold or gave away so much junk/tools I didn't need, but I'm losing my mind watching my projects decay. If I just had room to get a car IN and have some space to work I could retrieve some of my sanity.
I've been watching for 5 years for something close by with a decent shop rental or a property for sale with a garage on it but around here that means commercial. To get anything where there isn't the restrictive zoning means driving nearly 45 minutes. Closest thing I found near me was a questionable/crumbling building for $575k and the taxes were $550/mo.
VolvoHeretic said:Find out what the property line setback for a non-attached garage is. Some places it is only 3 feet, especially in an older neighborhood. Is there enough space in the front to move the garage forward? Build a new thickened edge floating slab garage. I had a friend who literally split his garage in two down the ridge line, rolled half of it over on pipes onto a new slab extension, and added new roof bottom and top chord boards. Crazy, but it worked. You could add new trusses and make it much easier
Setbacks are 5' to one side, 25' to the other, 5' to the back. That's what the rules say. Whether or not they'll fudge for an old property is anyone's guess. No space to move forward, at least not enough to get setbacks, however (in one of my rambling posts) I think my back line is already 5-6' behind the garage. I might be fine there.
Thickened edge slab is a no-no. Must be below frost round these parts. I think if I were to keep the current slab, my only hope is to cut it back 8" on three sides and dig down for a frost foundation, then pour the foundation and the additional 6' of slab. But if I'm going that far (and since I have no idea how thick the current slab is) I might as well demo the old slab and start from scratch.
I keep feeling like this is an all-or-nothing proposition. I can build a lean-to and get a little space, or I can drain most of my savings building new.
Get a piece of rebar and pound it down along your foundation block wall and see if there is a footing down there and how deep. That will let you know what it will take to match the new addition to so that you have equal load or frost heave distribution. If no footing dig an exploratory hole to find out how deep the foundation goes and just match that with a thickened edge slab if it's not too deep. We still need to know how tall your side wall is. 
Instead of a lean-to, run the new ridge 90 degrees to the existing garage, place your beam on top of the existing wall and back frame the new roof over onto the existing roof. Or, run the lean-to up onto the existing roof so that you cover the beam. I can draw you a diagram if you give me close enough measurements.
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