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Building a cistern  

 

stcroixboy
(@stcroixboy)
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June 3, 2011 12:52 pm  

Anyone ever build a cistern out of blocks and just had the whole thing plastered inside/out?
This is a lot cheaper than pouring the whole thing.
Of course I'd fill/reinforce each block tho.
What do the building codes say?
I'm looking at about a 20,000 cistern
Say 15x25x7 finished I.D.

Thanks.


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Bombi
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June 3, 2011 1:25 pm  

If you build on undisturbed soil , install a vinyl water dam between the walls and the floor, fill every void with concrete and reinforce with rebar sized appropriately, and apply a bonding agent to the block and then plaster it will work. The issue is the frequency of seismic activity in the VI that could cause cracking. I think poured concrete is way better and easier to maintain. I have seen quite a few block cisterns with leaks.


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Jumbie
(@ohiojumbie-2)
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June 3, 2011 3:04 pm  

Yes our cistern is made from blocks, reinforced with rebar, then coated with concrete inside & out.

Bombi's statement about a vinyl barrier between the walls & floor is only way to go in order to prevent leaks. Many cisterns are made from block, rebar, & coated with cement or plaster. However also quite a few are made from poured concrete. Both will leak from all the seismic activity regardless of how much re-inforcement you have in the walls/floor.

Here's an excellent supplier of cistern liners for potable water. The Web site is: http://www.dlmplastics.com/

We had one installed last November and don't have to worry about re-sealing the block walls every 3-4 yrs. DLM Plastics is in Findlay, Ohio and the contacdt name there is Tony Marshall. His phone number is 419-424-5250 (ext 5269). They custom make the liner to the cistern measurements. Material plus install (can do it yourself or hire it done) will soon pay for itself by not having to re-seal leaks. The liner should last for 15 -20yrs.

Jumbie -STX


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stcroixboy
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June 4, 2011 4:17 am  

Yes our cistern is made from blocks, reinforced with rebar, then coated with concrete inside & out.

Jumbie -STX

Is your cistern totally above ground? totally below ground or only a little below ground?
And yours is about 10,000 gallons correct?
What'd they charge you for the vinyl liner alone? Not labour or anything.

Thanks.


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stcroixboy
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June 4, 2011 4:19 am  

If you build on undisturbed soil , install a vinyl water dam between the walls and the floor, fill every void with concrete and reinforce with rebar sized appropriately, and apply a bonding agent to the block and then plaster it will work. The issue is the frequency of seismic activity in the VI that could cause cracking. I think poured concrete is way better and easier to maintain. I have seen quite a few block cisterns with leaks.

I read that you poured your entire house. Have any pics or a building blog floating around for me to see? Quite curious of it all.

Thanks.


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Jumbie
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June 4, 2011 9:32 am  

Yes our cistern is made from blocks, reinforced with rebar, then coated with concrete inside & out.

Jumbie -STX

Is your cistern totally above ground? totally below ground or only a little below ground?
And yours is about 10,000 gallons correct?
What'd they charge you for the vinyl liner alone? Not labour or anything.

Thanks.

Our cistern is underneath the bedroom and since our 2 story house was built into side of a hill, that leaves one wall "above ground" while the side walls are partially "underground". Cistern liner was approx 14x14x10, capacity about 12,000 gallons -material cost was $1250, freight from mfgr to STX was $390 on 231#. Labor to install was more than material & freight.

Jumbie -STX


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Bombi
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June 4, 2011 1:11 pm  

I read that you poured your entire house. Have any pics or a building blog floating around for me to see? Quite curious of it all.

Thanks.

No blog about building. But is a photo. It now is a lilac color and has wood shutters on all the openings. My theory was to build to 200+ MPH and forget about $$$ windstorm insurance. It's bee through Omar with 100+ MPH winds, we slept through it.


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stcroixboy
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June 4, 2011 2:39 pm  

Cistern liner was approx 14x14x10, capacity about 12,000 gallons -material cost was $1250, freight from mfgr to STX was $390 on 231#.

Jumbie -STX

Hmmmm, I really have to crunch the numbers and see how much I'll save by doing a block cistern instead of poured. Since I have that liner would it even make sense to plaster the inner walls of the cistern? I know the cistern is usually the largest part of construction cost so that's why I have all the questions.

And I'll probably be better off with two of the liners you have and just build two 14x14x10 cisterns side-by-side so that way if one needs to be repaired I'll still have the other.

Thanks again.


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stcroixboy
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June 4, 2011 2:52 pm  

I read that you poured your entire house. Have any pics or a building blog floating around for me to see? Quite curious of it all.

Thanks.

No blog about building. But is a photo. It now is a lilac color and has wood shutters on all the openings. My theory was to build to 200+ MPH and forget about $$$ windstorm insurance. It's bee through Omar with 100+ MPH winds, we slept through it.

Your link didn't work [but I found a workaround 😉 ]
Your house is pretty neat.
Nice and simple.
It is similar to one that I had in mind but mine'll be about twice the sq ft of yours (room for youngins' and all).
And where you're sitting on your porch I'd have that depth (height) be 6 to 8 feet and make that be my cistern.
I don't know about the depth (front to back) of your porch but I'd estimate it's about 40ft wide, correct?

Am I doing things backwards?
I'd want poured exterior housing walls but a BLOCK cistern!
Usually people do block walls and a poured cistern.
My reasoning is purely for hurricane protection and the ability to not carry hurricane insurance.

But pouring the entire structure (house and cistern) will be MANY yards of cement!
What is the thickness of your exterior walls?
I've been researching on youtube and they have some wind test by a university in Texas.
Seems poured can withstand quite a bit.


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Bombi
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June 4, 2011 9:37 pm  

The norm here is 8 inch walls with one mat of #5 rebar 10-12 inches on center. I did a double mat of 5 bar 10 OC. . My little house has 125 yards of 3500 lb. concrete, total. The roof system is anchored to the rebar mat and all rafter connections are joined with galvanized, bolted, steel brackets. The roof is a sandwich of mold resistant drywall, 2 inch urethane foam and 3/4 inch T&G plywood, screwed @ 5 1/2 inch screws, with roof coating. No overhangs on the eves.
The block cistern will need to be plastered, the pored concrete just needs the tie rod holes sealed. I coated the outside with waterproofing tar.
i drew the basic plans and had a local draftsman do the required drawings. I have a friend who is an engineer and he gave me the parameters for 200 MPH and a local engineer confirmed the calculations.
The house is 26 feet wide and 36' long.I have a plan for a 36x50 three bedroom house that was going to be built next to it but I am totally happy with my little cottage and my $700/month mortgage.
. I store 10,00 gallons of water and that seems fine for 2 people but I wish I had 20,000.
Good luck with it.


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Exit Zero
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June 5, 2011 7:31 am  

Pour the cistern! - the $$ expense will be rewarded during your tenancy and at resale. Most cisterns are 2 compartments - they do not have to be equal - with the access hatch in the middle - that way one side can be used to maintain a normal lifestyle while the other side is repaired , cleaned and coated with very little inconvenience every 10 years or so.
The walls can be built from block and reinforced with rebar should you want more strength. Almost all the major damage I saw after Hugo 1989 and Marilyn 1995 was roof loss/ damage at the ring beam connection or window /slider /door opening failure and the resultant weather intrusion with continuing deterioration. Any lengthy porch or deck overhangs that were connected or cantilevered to/ from the main roof rafters were exposed wing structures that lifted and peeled away the whole roof - in many cases in 1 piece like a can opener.
Well designed shutter systems - that are easy to close and not labor or time dependent are essential - [electrically operated shutters are close to useless IMO ] - and plywood panels are heavy and if they require a ladder or aerial ballet should be avoided - it will be really windy the day you decide to put them up - A Ring Beam construction with Simpson ties and SS screws or the ?? equivalent is absolutely the best protection against roof loss - Hip Roof structures have been a proven storm worthy design all over the Caribbean forever. With strong shutters, no overhangs and solid hip roof/wall connections even wooden traditional West Indian houses have survived hurricanes here for centuries - usually their only damage is caused by the whole house lifting off of their unconnected stone pillar foundations.
It is not uncommon to see a block wall home retro fitted with an external and sometimes even an internal ring beam added - with a 2X10 plank epoxy bolted to the walls and Simpson strapped to the rafters. With no overhangs on the roof and every opening securely shuttered even this type of structure is likely to withstand Hurricane winds.
With a mortgage the guarantor usually requires Windstorm and possibly Earthquake Insurance - the better the construction and all added preventive mitigating improvements you can present to the insurer the better your chances at reducing the premiums.
If you can do the construction without pledging the property as equity collateral you can self insure in your own separate account,[ it takes personal financial discipline to write that check to yourself] BUT you will have it available immediately [!] without adjustors involved should you need it after a storm - look into pledging stock or another property as collateral instead of a mortgage or building loan.
Good Luck on your house building - it will be the most fun and frustrating - rewarding and demanding experience you will embark on in the Caribbean - but a nice cuppa coffee at sunrise or R+C at sunset there will be your treat every time.


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stcroixboy
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Joined: 11 years ago
Posts: 13
June 7, 2011 1:03 am  

The norm here is 8 inch walls with one mat of #5 rebar 10-12 inches on center. I did a double mat of 5 bar 10 OC. . My little house has 125 yards of 3500 lb. concrete, total. The roof system is anchored to the rebar mat and all rafter connections are joined with galvanized, bolted, steel brackets. The roof is a sandwich of mold resistant drywall, 2 inch urethane foam and 3/4 inch T&G plywood, screwed @ 5 1/2 inch screws, with roof coating. No overhangs on the eves.
The block cistern will need to be plastered, the pored concrete just needs the tie rod holes sealed. I coated the outside with waterproofing tar.

yeah in the grand scheme of things pouring might not be THAT much more expensive than correctly laying blocks.


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stcroixboy
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June 7, 2011 1:06 am  

Pour the cistern! - the $$ expense will be rewarded during your tenancy and at resale.

Thanks for the info but I doubt I'll be selling this place. Gift it to family if anything.


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