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Basement Wall Construction At Property Line

 
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Old 09-01-2017, 12:53 PM   #1
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Basement Wall Construction At Property Line


I have a new house project in Portland, Oregon which will require an attached garage wall to be built 18” from an adjacent property line at a depth to bottom of footing of about 8’ below grade. We’ve obtained planning permission to impose into the 5’ sideyard setback on the south side. The neighbor’s flat lot has landscaping up to the property line and the neighbor does not want his property disturbed. The garage wall will extend above grade and have a deck on top bringing the total height to 18” above finish grade, so the primary limitation is constructing the concrete basement wall. The street is several feet lower than the finish grade at the garage, and the driveway slopes down to the garage. The garage wall is 20’ long and the sloping driveway with a retaining wall is another 25’ or so.

The garage itself is designed for a boat, so that that owner can be ready to take it out at a moment’s notice, but keep it out of the weather and easily accessible, thus the garage is much smaller than is practical for most vehicles. It’s an urban infill project and the lot is very restricted, with only about 35’ of lot width we can build in (including the sideyard setback) and, after 4-1/2 years of working with the owner on various designs, we’ve slowly pushed the design closer to the property line.

I have worked in construction most of my life, but now primarily do just design. In my younger years, I participated in at least a dozen underpinnings of adjacent buildings that were at the property line, that required excavating new basements below level of the adjacent building’s footings. All of those jobs were labor intensive, requiring that we do the excavation and retaining wall construction in segments, with lots of wood shoring, etc., but while the risks were real, they were relatively easily accomplished and not extraordinarily expensive (example found on the web: https://ecohistorical.wordpress.com/...w-foundations/ ). These were all on very restrictive city lots, but small in scale, and did not begin to approach the kind of large commercial projects that require steel pilings, tie backs, or other methods of temporary shoring.

My assumption has always been that this current project’s garage wall at the property line would be constructed in a sequential, segmented way, with shoring, similar to what I am familiar with myself and what I often have seen others do on residential projects. At the beginning of the design process, I had given the owner a referral for a great builder I’ve worked with a number of times who does his own excavation and concrete work (he does sub out taller formed walls), and was generally a very hands-on guy who would have no problem taking on this sort of project. The owner did have a brief phone chat with him but never did any follow up. About two years ago, the owner decided they would be their own general contractor, and, in the last couple of months, have contacted several foundation contractors, two of which have given ball park estimates (there are no working drawings or engineering yet). One of the contractors estimates that the proximity to the property line would add at least $50k and the other said it would add $100k, and both have said it could only be done with soldier piling or steel sheet piling. He has also consulted with a professional architect who has advised him that the house is, cost wise, unbuildable near the property line.

Needless to say, these additional costs have thrown the owner into a bit of a frenzy. My question is, does anyone have any experience with smaller residential projects and less expensive shoring methods? Does the owner have no choice if he contracts the job himself than to either redesign the project or pay for expensive shoring?
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Old 09-01-2017, 01:33 PM   #2
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Re: Basement Wall Construction At Property Line


If I was a foundation contractor who was requested to bid that for a homeowner GC'ing for himself, you can count on the bid being much greater. Something that delicate, as building so close to a property line and a touchy neighbor, will need an experienced contractor who know's his *****. One delay b/c the homeowner didn't do something correctly can cost a lot of money.

Maybe he should reinvestigate having a contractor do the job and resign himself to it being a costly project b/c of what it is. Since you indicated it's for storing a boat, he shouldn't complain (y)

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Old 09-01-2017, 03:28 PM   #3
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Re: Basement Wall Construction At Property Line


You have the design of the house with the basement, great. Now it should go to an engineer to design a solution for not only the basement walls but for the shoring also.

I have worked with engineers on basement builds and they all had shoring solutions that seem a lot less expensive than what the contractor was suggesting it may cost.

Get the engineering solution first then have the home owner get the contractor.

Andy.
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Old 09-01-2017, 04:03 PM   #4
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Re: Basement Wall Construction At Property Line


It's hard for a contractor to just bid a what if scenario. Why wouldn't you want to have all the plans and specs before you talked to a contractor. Now the guy who is 50 grand up, can look at the plans and then say, oh, probably only 30 grand more and you client will be relieved. When in reality, it might not cost much more at all. I don't think you looked put for you client on this one.

That being said, I realize he jumped his own way. So maybe he will just have to pay to the school of hard knocks.

I assume you told him to get drawings and engineering before he talked to other contractors. If so, it's on him.

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Old 09-01-2017, 04:46 PM   #5
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Re: Basement Wall Construction At Property Line


Hmmm, best year in portland construction in a decade and a shortage of good competent foundation crews. They could do a bunch of easy mcmansion pours orrrrrr deal with a nickel and dime homeowner who wants to do crazy difficult work with a ton of potential risks. Tough call.

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Old 09-01-2017, 07:23 PM   #6
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Re: Basement Wall Construction At Property Line


I live and work in Portland - curious where the project is? Neighborhood and is it on one the buttes?
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Old 09-01-2017, 07:35 PM   #7
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Re: Basement Wall Construction At Property Line


It's in the Woodland Neighborhood in NE, just north of Dekum Street - Flat or very gradual slopes.
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Old 09-01-2017, 11:38 PM   #8
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Re: Basement Wall Construction At Property Line


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It's in the Woodland Neighborhood in NE, just north of Dekum Street - Flat or very gradual slopes.
We have done a lot of projects in that area of Portland and I can say without qualification, it is one of the best most stable soil’s in the city. Actually it is similar to most of the soils throughout the flat portions of the Willamette Valley. It was deposited from the Missoula Floods (search for the Nova program on it – fascinating stuff) and is mostly loam soils that can be hundreds of feet deep. There can be layers of gravel – everything from pea sized to fist sized layers and they can be a bear to hand dig in but they are mixed with loams and even more stable than the surrounding layers.

We have dug basement foundations 10’ deep into this soil with almost straight sides were stepping was impractical and not had serious concerns about collapse (and yeah, I get it it’s always a danger). We also dug one foundation and one retaining wall at property lines with complete success. On both of those projects we put a fence at the property line and never stepped foot on the lot next door during excavation.

With those two projects we did have shoring. Here’s what we did. Dug a 6’ to 8’ wide trench 4’ deep along the property line – the side next to the property line was sloped at about 45 degrees and the other side was straight down. Every 10’ feet on center we excavated a 5’ x 5’ x 5’ deep pit starting at the bottom grade of our trench at the property line side and lined the property line side with horizontal PT 4x6 on edge with 4x8 posts on either side braced into the opposite side the pit. The vertical 4x8s get drilled for rebar that will poke through into the yet undisturbed soil on either side and it also gets a vertical key form attached. The rebar in the footing below also gets driven into the soil in either side that will require hand excavating around it at the next pour. We put a drainage matt against the PT 4x6s and put our plywood forms on the outside of the 4x8 with vertical whalers and lots of bracing. That center bracing remains until the intermediate sections are formed and their concrete cured.

Once the first pour is cured we cut the edges off the plywood forms to make it easier to remove the 4x8s and repeated the process on the unexcavated portion. On the first job we did this on we mitered the ends of first pour sections 4x6s so that a complimentary miter on the intermediate bracing would fit between and just catch the new concrete, but on the next job we simply cut the soil flush between our newly poured wall sections and proceeded forward without bracing. Neither of these jobs had a slope above, so the engineer did not specify drainage tile or gravel.

I know that this is a terrible waste of good money on PT that is left in the ground, but it is a simple system that anyone familiar with concrete and dealing with deep form pours can do. We charged $15,000 for the 25' of basement wall, and a foundation company did the rest of the work. However, if another project comes up we will probably do something different. We’ll use a PT stud system with PT plywood, with or without a concrete footing, per the engineers direction. It was the engineer who suggested this PT foundation system on the basement foundation walls project, but the homeowner was skeptical. The advantage of this system is that you can work from one end of your wall to the other digging in 4’ sections and bracing as you go. No need to have the excavator there for multiple days for a small job if the walls sections are preassembled. There is a real advantage to when you need drainage gravel with this system.

My descriptions is not news to anyone familiar with construction and I’ve seen the topic and various methods of one sided forming discussed here and on other forums many times, but since you asked about others experience, I thought I’d ad my twocents. I’ll see if I can find some pictures of either project to post, but I’m a terrible chronicler in the digital age and ten or more years is a lifetime ago now.

Last edited by hausfxr; 09-01-2017 at 11:45 PM.
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Old 09-02-2017, 12:22 AM   #9
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Re: Basement Wall Construction At Property Line


$50-100k extra? I'd offer the neighbor $5k to rope off their landscaping near the property line for safety, and if anything sloughs off, pay for getting it redone. Agree with the above, seems like most excavations around here have tall vertical walls no problem.
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Old 09-02-2017, 01:57 AM   #10
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Re: Basement Wall Construction At Property Line


Thanks for the detailed reply Hausfxr.

I’ve mentioned the PT stud system to the homeowner, after having come across a reference to it online, and I know I first heard of the wood frame basement walls at least 30 years ago, so, if it’s still in use today, it must be a viable system. Your experience in general comports with my own experiences with underpinning foundations – it all comes down to good common sense and assessing the risk level. There is no reinvention of the wheel required.

Would you be interested in talking with the owner and possibly taking on some portion of the work?
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Old 09-02-2017, 11:23 AM   #11
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Re: Basement Wall Construction At Property Line


No thank you please on taking on the work or even talking with the owner. Except maybe if the economic situation goes haywire again, I’ll never work for a homeowner GCing again.

The last straw was in 2010 when I was doing the framing, windows install, gutters, and roofing portion of a job directly for a homeowner/GC and I showed up early in the morning to meet the roofing delivery boom truck. There were all of the homeowners kitchen appliances in the middle of the driveway from a delivery the day before – an 8 burner range, large refrigerator and equally large freezer, and their dishwasher. It would be at least three months before they could be installed! I have no handtruck and even with that, the stove would need a pallet jack or six strong guys to move and even if my guys where there, why should I risk injury to one of them for the owners stupidity. The roofing truck shows up and I have to turn them away. I tried contacting the roofers to see if they wanted the delivery on the curb (which I know they would not) or at least warn them away, but ½ hour later they show up. These are great guys who do very good work and I would hate to lose them as a sub. This was about the 50th thing like this, and we’d only been on the job for four weeks. I swore never never again.

My general view is that you have to charge three times what you would normally to work under a homeowner/GC. In your case the first thing I wondered about was what was going on with the design process taking 4-1/2 years? Big red flag. Even for you, you are potentially getting yourself into the precarious position of being intermediary between angry professionals doing the work and the owner. I promise you, the owner will blame you first in any and all disputes and so will those doing the work. Especially when the owner finds out that he has to pay a premium for any work both because he is GCing it and with the hot economy. Should have built 4 years ago.

I agree with ScipioAfricanus and VinylHanger that you need to get the wall engineered before you can get a realistic number. However, most professional engineers are going to be extra conservative to when dealing with an inexperienced homeowner, so you’ll at least need to find someone who is familiar with residential small scale construction – there is a world of difference often between methods employed on commercial projects and residential. And you don’t want to be determining the shoring method yourself in any way. That’s entirely the homeowner/GCs and a civil engineers responsibility. Show the homeowner methods that have been employed previously, maybe, but only as evidence that the wall can be built relatively easily. Be cautious in general - if the guy is looking to save pennies by GCing it himself he is going to be pinching everyone including you.
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Old 09-02-2017, 12:05 PM   #12
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Re: Basement Wall Construction At Property Line


That was an excellent post, HausFxr.

I subbed for an HO/GC twice, once framing, once electrical and plumbing. Phukking disaster both times. Never, EVER, again.

Home owners have absolutely no idea what it takes to actually run a job.


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Old 09-02-2017, 04:05 PM   #13
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Re: Basement Wall Construction At Property Line


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No thank you please on taking on the work or even talking with the owner. Except maybe if the economic situation goes haywire again, I’ll never work for a homeowner GCing again.
Hausfxr, thanks again for the feedback. I completely understand your sentiments.

Three questions for you, if you will:
  1. With the basement foundation you mention, how did you arrive at a price for the work and was that work just part of entire project you were building?
  2. If it was just a part of the larger project, did you consider subbing it out to the foundation guys?
  3. Per Golden View’s great suggestion, did you make any special concessions to the neighbor?
  4. Did you charge enough in the end for this portion of the project?
As to your very astute advice to not be involved in the design of the shoring method, I completely agree – means and methods are the purview of the contractor.

And a question for anybody who might know: The article I cite in my first posting states "you can use various proven techniques from rock to temporary wood walls to shore up their foundation". Anyone know what he means by the "rock" technique? https://ecohistorical.wordpress.com/...w-foundations/
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Old 09-03-2017, 12:56 PM   #14
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Re: Basement Wall Construction At Property Line


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1. With the basement foundation you mention, how did you arrive at a price for the work and was that work just part of entire project you were building?
Not sure I get your meaning here on price. We estimated the labor, excavator rental, concrete pumping, and so on. This portion of the project was part of a very extensive renovation and addition we were contracted to do.
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2. If it was just a part of the larger project, did you consider subbing it out to the foundation guys?
We often do our own concrete work with footings and short stem walls if wood forms will suffice. We have worked with some great concrete companies, but often the guys doing concrete form work are not the sharpest or best layout guys around (apologies to those that are) and they are trying to get in and out as fast as possible. They often get walls way out of alignment both in plan and elevation and get holdowns in the wrong place. When you have to do the framing that comes next you pay attention and no the consequences of errors and take the time needed to get things as close to spec as possible at the foundation level. We also often do complicated or small portions of job that we know a subcontractor would charge and arm and a leg to do, such as this basement wall we are talking about. This also eliminates scheduling problems. Small roofs we also often do ourselves just for these reasons. Many contractors who have their own employees do the same. You have that flexibility that contractors without employee/workers don’t have. So no we did not consider subbing this out.
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3. Per Golden View’s great suggestion, did you make any special concessions to the neighbor?
Nope – I’ve learned to leave that to the homeowner. Neighbors always hate any imposition (six months of daily noise, taking all the street parking, and etc.). Doesn’t mean we aren’t courteous and respect the nuisance laws, but you open the floodgates when you let the neighbors start dictating when and what you can do.
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4. Did you charge enough in the end for this portion of the project?
Does one ever charge enough. I don’t remember the exact fiqures that were put in the estimate from so long ago, but I do remember the final total and being quite pleased with ourselves. What I also don’t remember is whether that included overhead and profit at 30%. That number is part of the overall job cost.
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Old 09-04-2017, 07:36 PM   #15
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Re: Basement Wall Construction At Property Line


Thanks so much for the info. Just trying to get your perspective on risks vs. rewards of doing this kind of work yourself.

Find any pictures?
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Old 09-04-2017, 07:48 PM   #16
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Re: Basement Wall Construction At Property Line


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Nope – I’ve learned to leave that to the homeowner. Neighbors always hate any imposition (six months of daily noise, taking all the street parking, and etc.). Doesn’t mean we aren’t courteous and respect the nuisance laws, but you open the floodgates when you let the neighbors start dictating when and what you can do.
A little bit of a tangent, but there is an art to making neighbors happy, and it can be worth your money. Just being friendly, apologizing for the inconvenience, giving a starbucks coffee card, introducing yourself and giving your info so they can call if they have any issues usually is enough to make them never call you.

Recently I became the hero of the neighborhood (their words) by having my lady put together a bouquet of roses from our garden. I left it on the neighbors porch with an apology note for the noise (breaking up a slab, excavation for ADU). She was an older lady with limited mobility and a mean glare. She called gushing over my thoughtfulness and now has nothing but a smile foe me. My clients said I'm a genius because they had been worried all along about her interfering and being a thorn in our sides.
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Old 09-04-2017, 11:08 PM   #17
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Re: Basement Wall Construction At Property Line


good call GV, that's important when you're dealing with uptight or possibly uptight neighbors. I go as far as to picking up debris outside the gate on the job I'm subbing for, but keeping it tidy helps.

let's talk about designers parking in neighbors driveways...that will send a neighbor in a tailspin lol
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Old 09-05-2017, 10:17 AM   #18
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Re: Basement Wall Construction At Property Line


Anytime I need to excavate close to something that can't be disturbed and won't allow me to have adequately sloped banks that are safe per OSHA, I install sheet piling shoring to hold back the banks.

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