Holy ****!

[ForceFed70]

Just got my engineered foundation drawings from the structural engineer. Holy ****! This is going to be an expensive wall! All so that I can backfill to 6' high.

Must be MPA32 concrete or better
12" thick wall
4'7" wide footing, 12" deep
And what must be 100's of pounds of steel

Hope it turns out to be worth it.

 

[blue dog]

Just got my engineered foundation drawings from the structural engineer. Holy ****! This is going to be an expensive wall! All so that I can backfill to 6' high.

Must be MPA32 concrete or better
12" thick wall
4'7" wide footing, 12" deep
And what must be 100's of pounds of steel

Hope it turns out to be worth it.

Where are you located? I would assume more then just hundreds of pounds of steel.

 

[ForceFed70]

Where are you located? I would assume more then just hundreds of pounds of steel.

British Columbia, Canada

Not sure what the rebar will weigh, but there's no doubt it will be a lot. At least 10x the amount of steel that is called for in a regular wall.

 

[Torque1st]

Most "standard" or "regular" foundations are totally inadequate. They are just strong enough to last through the building warranty period if you are lucky. When they crack you get the standard excuse: "There are only two kinds of concrete, the kind that is cracked, or the kind that will crack."

 

[blue dog]

Is this a retaining wall that is holding back earth? if so, how many feet of dirt deep is it holding, sorry , your canadian, metric equivalent. I assume you have a frost line you have to go below. Make sure and waterproof the the sections of wall that will be below the earth
BC is big, north or south?

 

[cowboyjosh]

If thats what an engineer called for, thats what I'd go with. I like to over build, no one has ever come back and said "your house fell down" or "the foundation is fu*ked up".

 

[ddawg16]

Most "standard" or "regular" foundations are totally inadequate. They are just strong enough to last through the building warranty period if you are lucky. When they crack you get the standard excuse: "There are only two kinds of concrete, the kind that is cracked, or the kind that will crack."

No kidding.....

In relative terms, concrete is cheap....my 20'x25' foundation used 20 yards of concrete. In building my garage I learned a lot....like, a lot has changed from 50 years ago...even 15 years ago. My inlaws house (over 4000 sq ft) was built about 20 years ago.....looks great on the outside. But if you open up a wall, you start to see short cuts taken.....they have a sunken living room...about 18" below grade.....water damage has been a major issue over the past 5 years. They got it fixed now but one of the problems was that proper drainage was not accounted for and the slab was poured seperate from the stem wall....and the stem wall was not high enough.

Good chance what the engineer gave you is designed to last a loooonnnnnggg time....as they say, better to do it right than do it over.

 

[scooby074]

I think BC's building standards have gone way up as they anticipate "the big one". That and the previous scandals involving shoddy building practices that made the news in the last few years.

 

[ForceFed70]

Is this a retaining wall that is holding back earth? if so, how many feet of dirt deep is it holding, sorry , your canadian, metric equivalent. I assume you have a frost line you have to go below. Make sure and waterproof the the sections of wall that will be below the earth
BC is big, north or south?

Southern Interior of BC, Kelowna is the name of the city.

Yes, it's a retaining wall/foundation wall combo. I was planning to design it to hold back 6 feet of earth, but had the engineer chart the different requirements for different soil heights. The only difference between 6' and 7' is a 6" wider footing, so I will probably build it to hold 7'.

2' minimum footing depth for frost protection. I will definately be water-proofing and putting in lots of gravel and drainage tube/tile. Don't want any water in the garage!

 

[ForceFed70]

Here is a copy of the drawing if you're interested.
There is a lot going on in this drawing, hope I read it all correctly

 

[blue dog]

In my experience, i would say it is a bit over engineered, but that is what they do, otherwise, it is straight forward and a good design, stick with what the engineer has drawn. There really is not a lot going in there,his curing brace is something i would not do and wait the 28 days till cured and then backfill.
I would assume that your building department fallows what they do in Vancouver. As time goes by, engineering is becoming far more complicated and over designed.

 

[GarageEnvy]

I won't weigh in on what the specs should be but I will suggest that you talk to contractors for alternatives. In my case an engineer spec'd 2 Simpson Strong Walls that cost $2,000 and couldn't be built as drawn. Went through plan check and everything. Contractor simply suggested a couple extra larger anchor bolts and double-shearing the wall. Total cost was $30 and inspectors approved it. Sometimes there is an easier and cheaper solution.

 

[Weedwaka]

Are you holding up the bottom of a mountain or something ? I would get a second opinion before building that. What did they charge you for that drawing ? We are in Salmon Arm, holding back more than 6' with 6" thick ( very rebar filled ) walls. 4' for frost here and were an hour drive from you.

The "engineering" department that designed our roof and floor system made us do 1.5' deep x4' square footings jammed with rebar for our main posts, then told us we could use 3 nailed together 2x6's instead of the posts they shorted us. Idiots. 2x6's would explode before that footing moved a mm.

Also, who called for the engineering and why. 6' is in the book for reinforcement structure. You shouldn't have needed an engineer unless something else was going on there. I have a book here somewhere with wall details

 

[jimp]

Looking at your drawing, I am assuming that you have your slab 6' below finished grade (yes, I read your post, 6' of backfill).

If I am correct, I do not see that your wall is over "engineered". Most people will look at this like a basement, it is not. In a basement you have the first floor platform act as a structural member. In that case your wall is aided by your slab and platform. If you notice in a normal basement drawing, the rebar would have been placed in the inner 1/3 of the wall because all the pressure on the wall would place the inner wall in tension. On your wall, you do not have that top platform. So the pressure from the soil is putting the inner wall in compression and the outer wall in tension (vertically). Your engineer placed the rebar in the outer 1/3 of the wall, he has designed you foundation wall to be a retaining wall.

I am personally a belt and suspenders type, so I would have (and did on my own house) place a double mat of rebar (one 2" from the outer wall and one 2" from the inner wall).

I assume your engineer evaluated the soil type, if so, I would not second guess him. A few 1000 #s of rebar and concrete is cheap compared to a wall failing.

 

[blue dog]

Are you holding up the bottom of a mountain or something ? I would get a second opinion before building that. What did they charge you for that drawing ? We are in Salmon Arm, holding back more than 6' with 6" thick ( very rebar filled ) walls. 4' for frost here and were an hour drive from you.

The "engineering" department that designed our roof and floor system made us do 1.5' deep x4' square footings jammed with rebar for our main posts, then told us we could use 3 nailed together 2x6's instead of the posts they shorted us. Idiots. 2x6's would explode before that footing moved a mm.

Also, who called for the engineering and why. 6' is in the book for reinforcement structure. You shouldn't have needed an engineer unless something else was going on there. I have a book here somewhere with wall details

When all is said and done it will be holding back 6' to 7' of earth, what is drawn is proper and will do it's job with out worrying about failure. There is a lot of force behind that much earth stacked, after looking at it again, i would run with it. Let it cure properly prior to applying waterproofing.

 

[Rte66Charlie]

Go with overbulit - you can't go wrong.

Canada is on high alert, they don't want Mike Holmes coming in and bitchslapping them and pointing out how it should have been done right the first time!!

 

[jhelrey]

It says this is required if back filled before concrete has set for 28 days. You may not need to do all of that unless you back fill the concrete within the 28 days.

 

[Holedgr]

When all is said and done it will be holding back 6' to 7' of earth, what is drawn is proper and will do it's job with out worrying about failure. There is a lot of force behind that much earth stacked, after looking at it again, i would run with it. Let it cure properly prior to applying waterproofing.

Blue dog....why do you say this? In my experience, any exterior coating, unless exposed or requiring fully cured crete, will not adversely affect the curing or quality of the process. Thanks.


-T

 

[blue dog]

Blue dog....why do you say this? In my experience, any exterior coating, unless exposed or requiring fully cured crete, will not adversely affect the curing or quality of the process. Thanks.


-T

In reality it probably does not make a difference, but the principal behind letting the concrete cure prior to applying waterproofing is that it will force the concrete to cure at a uneven rate due to the moisture that has to wick out is forced to exit one side as opposed to both sides. you want concrete to cure slowly and evenly,thus after the forms are stripped, we normally will spray the concrete down a few times a day with a hose for a week after the pour.
You must realize that i am Los Angeles and our weather is very different then where you are, matter of fact, is it not getting a bit late to form and pour concrete in your area due to freezing?
You will not be loosing time by not waterproofing, the rest of your build can continue and the waterproofing will either be sprayed on or rolled and can be done quickly. Make sure to sink a french drain in your gravel before backfill to pull water away from your foundation if you get a lot of rain.
I am not that familiar with your area, but have done 2 projects south of Calgary in the past, and found the engineering required to be of normal practice.
Side note, i have traveled most of BC and found it to be a very beautiful place and all the people i came across were great. I could live there in a heart beat.

 

[Daniel Dudley]

Last few I built of similar spec were with a 36'' footing and a ten inch wall with similar rebar. Not a whole lot different.

I LIKE REBAR.

 

[srmofo]

It says this is required if back filled before concrete has set for 28 days. You may not need to do all of that unless you back fill the concrete within the 28 days.

That's referring to the braces to support the wall

 

[ForceFed70]

Thanks everyone.

To recap some of what's already been said:
- Code in my area actually says you can backfill up to 7'6" on a laterally supported foundation wall without engineering. But for it to be considered laterally supported, the wall has to go all the way up to the roof joists (or floor joists on a 2 story). Since my ceiling is going to be 12' high, that really wasn't an option for me.
- The anchor blocks are only needed if backfilling prior to the concrete hardening to 3000PSI (28 days for standard 32MPA crete). I plan to just wait it out, but the engineer said that the concrete companies have additives, etc that can speed things up to just 4 days.
- I do have a short hill that I am holding back. Approx 50' high. I personally think that this wall is way over-engineered but I will be building it as the engineer says. Not just because I want to, but because I don't have a choice. The engineer and the city will both be inspecting it.

 

[Slick50]

If this wall will be part of the inside of your garage wall (exposed) you might consider some closed cell foam insulation on the outside prior to backfilling, especially if your garage/shop will be heated.

 

[mball]

I have a garage that is underneath the house and so is below grade on 2 sides. When we moved in I had a horrible problem with water and ended up diggiing everything out, putting in drain tile and a sump pump, waterproofing the wall with tar and plastic and backfilling with lots of gravel. The only thing I would recommend differently is research different waterproofing materials other than tar. I know there are better solutions. Also, like previously mentioned, consider styrofoam insulation on the outside of the wall for insulation purposes. IMO there is no such thing as overkill when it comes to waterproofing. It is a lot cheaper to do it now than to dig it up down the road and do it again! Good luck!

 

[blkhonda1991]

Southern Interior of BC, Kelowna is the name of the city.

Yes, it's a retaining wall/foundation wall combo. I was planning to design it to hold back 6 feet of earth, but had the engineer chart the different requirements for different soil heights. The only difference between 6' and 7' is a 6" wider footing, so I will probably build it to hold 7'.

2' minimum footing depth for frost protection. I will definately be water-proofing and putting in lots of gravel and drainage tube/tile. Don't want any water in the garage!

are you sure about the 2' footing depth for frost, seems way to shallow and the drawing doesnt call out a depth just the height of the wall from the grade line

 

[blkhonda1991]

Thanks everyone.

To recap some of what's already been said:
- I do have a short hill that I am holding back. Approx 50' high. I personally think that this wall is way over-engineered but I will be building it as the engineer says. Not just because I want to, but because I don't have a choice. The engineer and the city will both be inspecting it.

this is exactly why its engineered the way it is because it is a retaining wall not just a simple foundation wall. you are holding back that hill with the wall.

 

[ForceFed70]

are you sure about the 2' footing depth for frost, seems way to shallow and the drawing doesnt call out a depth just the height of the wall from the grade line

Yes, I'm sure on the 2' footing depth. It's 4' for clay soils which thankfully, I do not need to worry about.

The drawing shows the dimension and implies that it is 2 feet(if you consider that the footing is 12" thick), but it isn't actually marked because they do not know my soil type.

 

[ForceFed70]

Did the math today. This 32' long wall is going to require roughly 1600' of 15mm (5/8ths) rebar. (80x 20' lengths) Ouch!

 

[WNYflyer]

Based upon my interpretation of the engineers drawing,

Be careful. Even though your engineer didn't dimension the frost depth looks like he is actually saying it is 3'-0". Per the bar chart your engineer has a hard dimension "dowels into stem" of 7'-9" for a differential backfill height of 6'. Basically this say's that the stem is 8'-0" (7'-9" + 3" clearance vert. bar to top of conc. wall). Then you have the 1'-0" thick footing. Therefore 8'+1'-6'=3' frost

He may have inadvertantly tied the dimension down without realizing it. Better clarify with him to make sure you have a handle on what is really required for your situation and before any rebar is fabbed.

And the design is pretty much nuts on for a straight forward retaining wall.

As others have said, I would waterproof (not damp proofing) and insulate that wall now. But usually comes down to $$. I would have the engineer specify the drain pipe, backfill around the pipe and any filter fabric required so you know what you should have rather than having someone else telling you what he is going to put in. The engineer should have a standard detail or notes for that. Should cost you little if anything for that info.

 

[Torque1st]

Did the math today. This 32' long wall is going to require roughly 1600' of 15mm (5/8ths) rebar. (80x 20' lengths) Ouch!

Not "Ouch".

I used more than that in my driveway and it is only 75' long.

 

[blkhonda1991]

Yes, I'm sure on the 2' footing depth. It's 4' for clay soils which thankfully, I do not need to worry about.

The drawing shows the dimension and implies that it is 2 feet(if you consider that the footing is 12" thick), but it isn't actually marked because they do not know my soil type.

You know canadian code better than i do but if there isnt an explicitely stated dimension dont ever assume what it is even if you scale it on a drawing marked with a scale, all of our drawings leave our office with a note to not scale dimensions off the drawings since they arent always drawn to scale or printed to scale

 

[Holedgr]

Thanks for the response, BLue dog...I agree with your view....I think it's not crucial with a foundation as much with a cosmetic (visible) application....all good stuff though....caution...overkill...good stuff.


-T