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Do you leave plastic footers and sonotube?

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35 replies to this topic

#26 foste1cc

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Posted 20 April 2018 - 12:11 PM

I'm still waiting on my sonotube and footer to be shipped. I guess with the weather we've had in Michigan lately it doesn't make a difference that I don't have them yet. I plan on pouring a 4'x4' slab about 5' down that will sit under my plastic footer and sonotube. Is it better to let the slab cure before I place and pour my footer and tube? Or should I try and do it all in one go? 



#27 roscoe

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Posted 21 April 2018 - 12:42 PM

you can let the slab cure...or at least harden, before you move on...but have some rebar sticking out, and roughen the surface - house carpenters run a rake across the top of the footings before the crete sets.... so the pier will stick as much as possible...and keep dirt off the top of the footing so the bond will be good....  but then you can set your bigfoot and sono, and best to bury the bigfoot to keep it from floating when you fill it.  As you fill, pack your dirt real well every couple of inches to make it as firm as you can (but don't do that to empty sonotube or you'll cave it in. )

 

A 4x4 slab with a pier on top will easily carry basically any telescope that anybody short of Elon Musk can afford, you'll be all sorts of stable here.


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#28 Cliff Halliwell

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Posted 21 April 2018 - 05:54 PM

Just a word of advice on sourcing the concrete: check the price of getting a cement truck to deliver pre-mixed, ready-to-pour against the price of buying the equivalent amount in sacks and hand mixing it.  

 

When I did my observatory deck footers and telescope concrete pier it turned out to be slightly cheaper to get the mix delivered, to my surprise.  The delivery included a half hour of pour time, so a couple of neighbours with wheel barrows turned out to be handy.  

 

You can also order it with options to make it more durable, like air entrainment which adds tiny bubbles, which limit the run of micro cracks, or even some shredded fibre (fibreglass I think, although I could be wrong, as I did mine nearly ten years ago) which does something similar.  

 

Of course, if you want to build some big muscles, hand mixing is a good workout.


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#29 roscoe

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Posted 21 April 2018 - 07:01 PM

a 4' x 4' x 1' thick slab is about 2/3 yard.... about 25 bags of premix....assuming .6 ft3 per bag.... which is not too bad in a small mixer, but arduous in a wheelbarrow.  Around here, there is a minimum delivery price, which works out to that anything under 3 yards costs as much as 3 would anyhow....


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#30 foste1cc

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Posted 23 April 2018 - 11:30 PM

Thanks for these replies. I now have an understanding a plan to go about once my sonotube and footer arrive. I'll also try and calculate up how much concrete i'll be using and check prices. I'm probably pretty close to 3 yards. Thanks!

 

Carl


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#31 DrAstro

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Posted 29 August 2021 - 10:26 PM

When in doubt, read the installation manual for the product you intend to use.

 

https://www.bigfoots...docs/manual.pdf

 

But here is the overview from the instructions....

 

1.2 BELOW GRADE APPLICATION MODELS BF20, BF24 AND BF28 (DRAWING BFS-102)

1. After determining which Model Bigfoot Systems® Footing Form and construction tube size is
required for your application, excess rings above the ring diameter required must be removed with a
utility knife, hand snips or saw and discarded. {example: if you are using a 10 in. (25.40 cm)
medium construction tube with the Model BF24 remove excess plastic at top of medium 10 in.
(25.40 cm) ring thereby discarding the 10 in. (25.40 cm) small and 8 in. (20.30 cm) small, medium
and large rings.}

2. Attach the required length of construction tube to Bigfoot footing form with a minimum of four
3/4 in. - 1 in. long (19.1 mm - 2.54 cm) wood screws.

3. If the construction tube frays inward when cut with a handsaw, remove excess frayed tube
material with a utility knife for ease of application.

4. Place the Bigfoot in the excavation on top of undisturbed soil or 4 in. - 6 in. (10.16 - 15.24 cm) of
compacted crushed stone or gravel, level and have inspected by a Building Inspector if necessary,
then backfill in accordance with section 4.0 “Backfill for Below Grade Applications”. The Model
BF36 footing form must be placed on level undisturbed soil or on 4 to 6 inches (102 to 152 mm) of
compacted crushed stone or gravel. Align the Bigfoot and construction tube with batter board lines,
plum and brace as shown in (Drawing BFS-103).

 

5. When backfilling avoid dropping or placing heavy rocks or heavy wet clay on Bigfoot Systems®

footing form.

6. If the tube height above grade exceeds 3 ft. (0.91 m) the tube must then be braced in accordance
with Section 3.0, “Bracing” in the Installation Manual (See Drawing BFS-103).

1.3 BELOW GRADE APPLICATION Model BF36 (DRAWING BFS-102)

1. See #1,2, and 3 Below Grade Application for the Models BF20, BF24 and BF28

2. Align batter board lines, plum and brace as shown in Figure 2- Typical Bracing during construction.

3. Backfill over the footing form to a minimum height of 2 feet (610mm) from the bottom of the footing
form and compacted with a mechanical compactor. Continue backfill in 8- to 12-inch (203mm) lifts to
a maximum height of 5 feet. Compaction must be carried out between each lift. The concrete must be
placed in lifts that are 10 to 16 inches (254 to 406 mm) in height, with the concrete being consolidated
after each lift, as per previous instructions.

 

=============

 

I'm planning on using the 36" product in my observatory design. Be sure to check with your contractor (if you use one) and give them the instructions so they don't wing it. Also, I'm not sure if the box stores that sell this product can special order the 36" size. You might have to order it from the vendor and shipping is the price of one of the forms.

The guideline for a deadman underground system is to have 1 ton of concrete underground. If you bury this with the bottom 5ft underground with an 18" tube it works out to about a ton. The trick is to make sure your site has removable soil (no bedrock) down to 5 feet, otherwise you are going to have a very bad day!



#32 DSOGabe

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Posted 30 August 2021 - 01:56 PM

 

 

The important thing about concrete is to mix it right. Most people probably make it too runny, which is what really weakens concrete. And if you are self mixing, it might be worth the little extra bit of money to rent a mixer. Much better mix, faster, and really helpful if you have girly arms like me.

 

 

Definitely worth renting a mixer. I had a coworker help me in setting mine up. Between the 2 of us plus the mixer we finished pouring a 2x2x2 footer and a 48 inch tall 8" diameter pier in about 2 hours. I don't even want to think about how long it would have taken mixing by hand



#33 mmalik

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Posted 30 August 2021 - 03:34 PM

I don't even want to think about how long it would have taken mixing by hand

Principles of mixing by hand defined here...; all do-able by hand and by one person. N'th degree details in the same link. Regards


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#34 FrankG

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Posted 31 August 2021 - 12:39 PM

Principles of mixing by hand defined here...; all do-able by hand and by one person. N'th degree details in the same link. Regards

Your link fabulous and very timely for me. Many thanks



#35 speedster

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Posted 01 September 2021 - 08:37 PM

I'm a fan of Big Foot in proper application.  We are featured on their website.  Certainly not the best solution for a telescope pier though. For  telescope pier, spread footings = more digging, more concrete, more money, and more deflection of the pier.  You certainly still be happy but most everything about a spread footing design is working against you for a telescope pier.  Pier Engineering thread here on CN explains.



#36 macdonjh

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Posted 02 September 2021 - 09:08 PM

I'm a fan of Big Foot in proper application.  We are featured on their website.  Certainly not the best solution for a telescope pier though. For  telescope pier, spread footings = more digging, more concrete, more money, and more deflection of the pier.  You certainly still be happy but most everything about a spread footing design is working against you for a telescope pier.  Pier Engineering thread here on CN explains.

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