BajaNomad

Cost of concrete pad, roughly?

Alm - 4-9-2016 at 06:09 PM

Thinking to make a cement pad under my RV, 4" height, 16x28 ft size, 450 sq ft finished area. RV is 8ft wide so there would be small 8ft wide patio in front. Moderate slope of terrain, so there isn't much digging. Got tired of all the sand getting in and Ocotillo thorns cutting through my flip-flops.

Things like concrete truck don't exist in BOLA. From what I understand, trabajadores with this skills level cost anywhere from 80 to 140 pesos/hour. Everybody is jack of all trades or trying to promote their friends, whether they know how to do it or not - usual picture. Plus, something for use of cement mixer. Plus, cement. Plus, wire mesh to put inside - don't know if I need this. Don't know if I even need this pad :), but roughly, how much should I expect to spend, total?

4x4abc - 4-9-2016 at 07:41 PM

from $200 to $800
quality from bad to really bad
rebar in the wrong location
not enough cement for the salt exposure
concrete not condensed properly = your RV will be back in the sand in a few years

do it anyway
it's entertaining

or import a crew from Guadalajara - pay less and get good quality

Udo - 4-9-2016 at 07:51 PM

It would help if you would bring from the states a concrete vibrator, a concrete tamper and a set of long floats.
Quote: Originally posted by 4x4abc  
from $200 to $800
quality from bad to really bad
rebar in the wrong location
not enough cement for the salt exposure
concrete not condensed properly = your RV will be back in the sand in a few years

do it anyway
it's entertaining

or import a crew from Guadalajara - pay less and get good quality

Alm - 4-9-2016 at 10:00 PM

Quote: Originally posted by 4x4abc  

from $200 to $800
quality from bad to really bad
rebar in the wrong location
not enough cement for the salt exposure
concrete not condensed properly = your RV will be back in the sand in a few years

That bad? Few extra bags of cement I could afford.
I see some patios and pads of more-less decent quality, or few inches shallow foundations under casitas. Some others are ugly.

The idea was to add some roof later on, I thought 4" pad would make it easier to anchor the posts.
Might as well leave everything as is. Posts into the holes filled with cement, later, if it ever comes to this point. After BOLA had suddenly become a Mulege few years ago, I don't know if quality construction makes much sense.

[Edited on 4-10-2016 by Alm]

BajaRat - 4-9-2016 at 10:36 PM

Don't you think its a stretch to say you can't find quality Masons in Baja :?:

Alm, ask to see some finished work and ask the project owners satisfaction with job and price. Sounds like a worth while project to be more comfortable.
Good luck, Lionel

4x4abc - 4-9-2016 at 11:57 PM

Quote: Originally posted by BajaRat  
Don't you think its a stretch to say you can't find quality Masons in Baja :?:


I have met one decent contractor in 16 years (too late for my house).
And I have seen a single albaņil recently with beautiful concrete work.
That's it

All projects where quality is of the essence (Walmart, Home Depot, some hotels, some high end real estate) are done by crews from mainland

Mula - 4-10-2016 at 02:40 AM

Don't forget to put black plastic down first and then the mesh wire and then the rebar - and then the cement.

That's what we do here in Lopez.

Here in Lopez the cement workers get 250-300 pesos a day. I usually pay them 400 or 500 pesos.

We put a 30'X 15' slab down in San Nicolas a couple of years ago.
Crew - 6 guys and a cement mixer arrived from Loreto at 7 - started the mixer at 8 and 15 bags of cement later were done pouring the slab by noon. And another 3 hours to float it.

rocmoc - 4-10-2016 at 07:49 AM

Recommend a footing under the edge you drive upon the pad with your RV. I didn't do this and the edge cracked from the weight concentrated on the edge from the wheels. Also a footing at any point your plan to place a column support. Also recommend using two mixers to keep the concrete flowing.

rocmoc n AZ/Fld/Baja

[Edited on 4-10-2016 by rocmoc]

[Edited on 4-10-2016 by rocmoc]

bajaguy - 4-10-2016 at 07:56 AM

Salt will be your enemy

bkbend - 4-10-2016 at 08:55 AM

In Bahia you'll need to buy all the concrete, rebar, mesh, gravel and have it on-site so you will just be working out the labor cost with whomever does the work. Get them to do the footings, you may need to buy some rock and lumber for the forms.

Mexitron - 4-10-2016 at 08:57 AM

Quote: Originally posted by Mula  
Don't forget to put black plastic down first and then the mesh wire and then the rebar - and then the cement.

That's what we do here in Lopez.

Here in Lopez the cement workers get 250-300 pesos a day. I usually pay them 400 or 500 pesos.

We put a 30'X 15' slab down in San Nicolas a couple of years ago.
Crew - 6 guys and a cement mixer arrived from Loreto at 7 - started the mixer at 8 and 15 bags of cement later were done pouring the slab by noon. And another 3 hours to float it.


15 bags of cement for 450 sq ft is pretty low---that's five yards of concrete if the slab was 4" thick...should be closer to 25 or 30 bags for a 5-6 sack mix. Probably why "salt is the enemy", not enough cement, slab is too porous and salt gets in easier (also if using unwashed beach sand).

durrelllrobert - 4-10-2016 at 09:22 AM

Quote: Originally posted by Alm  
Thinking to make a cement pad under my RV, 4" height, 16x28 ft size, 450 sq ft finished area. RV is 8ft wide so there would be small 8ft wide patio in front. Moderate slope of terrain, so there isn't much digging. Got tired of all the sand getting in and Ocotillo thorns cutting through my flip-flops.

Things like concrete truck don't exist in BOLA. From what I understand, trabajadores with this skills level cost anywhere from 80 to 140 pesos/hour. Everybody is jack of all trades or trying to promote their friends, whether they know how to do it or not - usual picture. Plus, something for use of cement mixer. Plus, cement. Plus, wire mesh to put inside - don't know if I need this. Don't know if I even need this pad :), but roughly, how much should I expect to spend, total?
450 square feet x 4" thickness = 150 cubic feet = 4.247 526 988 8 cubic meter (which is how concrete slabs are measured in Mexico). You can buy Sakrete (cement, sand and gravel already in it) in 80 pound bags for $3.98 at Lowes in Chula vista and one bag will equal 0.60 cubic foot when 4 liters of water is added. Therefore you will need 250 bags for 150 cubic foot pour and that will cost $1,000 plus labor.

[Edited on 4-10-2016 by durrelllrobert]

Alm - 4-10-2016 at 10:59 AM

Thanks people, lots of useful tips.
"unwashed beach sand" - this is one of many things that scare me. Between my limited knowledge and their low standards I can imagine the results.

The footings would have to be around the entire perimeter. I don't plan on drive on and off too often, but posts/columns for roof are definitely in the plans. How deep should be those footings - another 4 or 6"?

4x4abc - 4-10-2016 at 11:30 AM

if the rebar is positioned correctly (in Baja it almost never is) there will be no need for footings.

I had 300 ft of wall collapse during one of the hurricanes due to shoddy work, wrong rebar, bad concrete connections etc. The wall had a hurricane design footing strong enough to support a 3 story house on top.

And that's another thing you might want to consider - Nature can be very violent in Baja. If your proposed pad is anywhere close to a surface water flow (even if it has been dry the last 100 years) your pad might become home for sea life.

https://carlosnpainter.smugmug.com/Other/Hurricane-Odile/i-M...

Alm - 4-10-2016 at 01:54 PM

4x4, you had really bad experience. I saw post-Odille photos in La Paz. In BOLA only the central part was flooded, but less destructive "surface water flows" were pretty much everywhere. There was just too much rain over very short time.

durrelllrobert - 4-10-2016 at 02:05 PM

Quote: Originally posted by Alm  
Thanks people, lots of useful tips.
"unwashed beach sand" - this is one of many things that scare me. Between my limited knowledge and their low standards I can imagine the results.

The footings would have to be around the entire perimeter. I don't plan on drive on and off too often, but posts/columns for roof are definitely in the plans. How deep should be those footings - another 4 or 6"?


2 things to consider:
1- is there any fill or thick layer of loose sand on the lot? Post footing need to be at least 8" thick with the bottom at least 12" into undisturbed native soil (see cartoon)

2- the portion of the steel post anchor that gets embedded into the concret is 4"" long and top of post anchor should be at least 1" above finished grade to protect 4x4 against dry rot.




Attachment: post pier.doc (23kB)
This file has been downloaded 256 times

AKgringo - 4-10-2016 at 02:24 PM

Just to add my two cents (36 centavos), I recommend spraying the slab with 'cure and seal' right after the last pass with the finish trowel. It slows the curing process which reduces cracking, and seals out salt, and some stains in the future.

We use it a lot in Anchorage where ice melters including rock salt are used on sidewalks and driveways. It should work by the sea shore as well!

bledito - 4-10-2016 at 03:44 PM

keep the top damp for several days using a hose or lawn sprinkler to keep it cool and slow the curing process. then you cam top seal it'

Alm - 4-10-2016 at 06:22 PM

Quote: Originally posted by durrelllrobert  

1- is there any fill or thick layer of loose sand on the lot? Post footing need to be at least 8" thick with the bottom at least 12" into undisturbed native soil (see cartoon)

2- the portion of the steel post anchor that gets embedded into the concret is 4"" long and top of post anchor should be at least 1" above finished grade to protect 4x4 against dry rot.

There is a loose sand with mud as usual :) - more mud than sand, after Odillo.

I was thinking of anchor bracket and bolt drilled/screwed into the finished pad later. Your anchor with footing is space age to me. In the attached cross-cut - this inverted concrete T-footing has to be formed and poured in, complete with anchor embedded, before the rest of the pad?

weebray - 4-11-2016 at 07:14 AM

If, like me, you are one of the unwashed masses you may want to disregard the above "cement" engineers and just go with the flow. About 20 years ago a friend recommended a local albanil to pour a 16 X 32 foot slab. Two sturdy men show up in the AM with a couple of plastic buckets of tools and a borrowed cement mixer. I only asked them two things: Please use more cement than you normally would and I would like the finished slab to be "muy liso". They laid down a roll of welded wire and went to work pulling up the wire with a hammer as they progressed. Later that day they stepped back and were rewarded with a cold one. My job was to keep the slab very wet for a few days. I recall flooding it for several days. I remember I could not believe how much water it absorbed. Twenty years later we have a beautifully smooth slab with a few minor cracks of no importance. No sealer, no additives, no problem. Ask a friend for a good albanil, stop pondering the job, go for it.

durrelllrobert - 4-11-2016 at 07:32 AM

Quote: Originally posted by Alm  
Quote: Originally posted by durrelllrobert  

1- is there any fill or thick layer of loose sand on the lot? Post footing need to be at least 8" thick with the bottom at least 12" into undisturbed native soil (see cartoon)

2- the portion of the steel post anchor that gets embedded into the concret is 4"" long and top of post anchor should be at least 1" above finished grade to protect 4x4 against dry rot.

There is a loose sand with mud as usual :) - more mud than sand, after Odillo.

I was thinking of anchor bracket and bolt drilled/screwed into the finished pad later. Your anchor with footing is space age to me. In the attached cross-cut - this inverted concrete T-footing has to be formed and poured in, complete with anchor embedded, before the rest of the pad?

..and make sure the posts are plumb in both directions before concrete cures.