Wall building advice

[bluesofa]

We're planning to build a boundary wall to enclose one and a half rai of land.
The height will be 2 metres (this seems about a standard height?)
Going to use standard breeze blocks. The total length of the wall will be about 180 metres.
A local builder has quoted labour at 550 Baht/metre of wall - build, then cement & paint one side.
That leaves us to provide materials.

That raises questions for those who might know:
How far apart would anyone suggest the concrete posts should be - 2, 3 metres?
Is there a rule of thumb for how many blocks per metre needed?
My g/f was told blocks are 4 Baht each, I noticed however in an earlier post someone mentioned 7.5 Baht per block. (I do rememeber 15 years ago buying blocks, the cost then was 3 Baht)
Is cementing only one side of the wall sufficient - will the weather eventually degrade the un-cemented side?
Plus, any comments or suggestions?

[cooked]

They generally plant the posts 350 -400cm apart.

Question: are you expecting to backfill? If so something sturdier than 8cm cement blocks will be required. For a 200cm high wall, you need 25 blocks/meter. We paid ฿4.90 per block, for larger quantities you should be able to beat that down, we delivered ourselves.

I think you really should cement wash both sides, but up to you really.

Some kind of coping stone on top makes a wall look classy, you can do it later.

Edited August 17, 2013 by cooked

[bluesofa]

They generally plant the posts 350 -400cm apart.

Question: are you expecting to backfill? If so something sturdier than 8cm cement blocks will be required. For a 200cm high wall, you need 25 blocks/meter. We paid ฿4.90 per block, for larger quantities you should be able to beat that down, we delivered ourselves.

I think you really should cement wash both sides, but up to you really.

Some kind of coping stone on top makes a wall look classy, you can do it later.

Thanks for your reply.

I get the impression that the owner is going with additional posts - horizontal at the bottom of each section so that the blocks sit on them, then another horizontal post along the top of the blocks.

I've seen a few walls like this.

Why would it need something better than the 8cm blocks at the bottom if it was filled?

[cooked]

Why would it need something better than the 8cm blocks at the bottom if it was filled? Because they won't hold if backfilled. Try googling coolhouse.com, they have lots of good advice there.

I must admit that these walls look better when there are more posts.

[krisb]

At 550baht a metre plus you supply is gonna cost a fortune! Anyhow those blocks are about 4 or 5baht. Posts are ok at 3 metres apart. We just went over it with a builder a couple weeks ago. We got priced 160,000 including materials plus painting is extra. Land size for us is half rai. Your bill must be up near 500,000?

[sirineou]

I paid 450 per linear meter for labor plus material about two years ago in Khon Kaen, 450 to 550 seems to be the going rate for labor depending on location,

with material it ended costing about 1200 bht per LM (one side finished except the front where both sides were finished)

[Khun Jean]

I like 'green' walls better.

Less of a prison feeling and cheap to make when you have patience.

We did a 'wall' around 7 rai about 5 years ago with only seedlings, spend if i remember correctly 3000 baht for the seedlings and two days work for two people.

Use only when not afraid to do regular trimming.

http://en.wikipedia.org/wiki/Bouganvillea

[Resa]

I like 'green' walls better.

Less of a prison feeling and cheap to make when you have patience.

We did a 'wall' around 7 rai about 5 years ago with only seedlings, spend if i remember correctly 3000 baht for the seedlings and two days work for two people.

Use only when not afraid to do regular trimming.

http://en.wikipedia.org/wiki/Bouganvillea

Are those Bouganvillea spreading all over your place? We plan to do the same but Im a bit hesitant to bring in what might become an uncontrollable pest...

[Khun Jean]

They are cut/trimmed every month.

Branches that grow the wrong 'way' are cut of completely leaving most branches going sideways.

It works when you not let them grow too high otherwise they tend to bow.

About 2m high 150cm deep works ok.

They do not seem to spread, only grow where we planted them.

Edited August 29, 2013 by Khun Jean

[transam]

The important thing is the post pads under ground. Think our walls have 2.5 m between posts. If not rendered both sides water will ingress and stuff your paint inside.

I will try and photo something tomorrow near me regarding the pads.

[bluesofa]

The important thing is the post pads under ground. Think our walls have 2.5 m between posts. If not rendered both sides water will ingress and stuff your paint inside.

I will try and photo something tomorrow near me regarding the pads.

If you can photograph them I think that will be beneficial, as it sounds like it could be an important tip - thanks.

[transam]

Have seen folk buy the ready made posts that have small pads, a cheap way out but can cause movement probs. My place l watched them make the metal frames, which had big pads/feet. Poured concrete on the feet to make the pads, then boxed in the frame to pour concrete with metal sticking out for the brick mortar to cling too.

[transam]

The important thing is the post pads under ground. Think our walls have 2.5 m between posts. If not rendered both sides water will ingress and stuff your paint inside.

I will try and photo something tomorrow near me regarding the pads.

If you can photograph them I think that will be beneficial, as it sounds like it could be an important tip - thanks.

.............

[bankruatsteve]

Looks like it wasn't planned out for retaining vs. just a wall. There's dozens of ways to do it proper. One is to put in anchors on the fill side. Google it.

[Greenside]

If you decide on a hedge, remember to put in a dog proof barrier of some kind in the middle of it. Don't use the flimsy galvanised wire fencing as it rusts through in a couple of years and do bury the bottom of it in the ground and curve it either inward or outward at least 30cm under the soil, depending if you are trying to keep animals in or out. It's too late to do this once your hedge grows. Also, bougainvillea clippings are a pain in the neck to dispose of - leave any around and sooner or later you'll step on a thorn that will go right through your flip-flop and I've lost count of the number of flat bicycle tyres we've had to fix!

Edited August 31, 2013 by Greenside

[transam]

Looks like it wasn't planned out for retaining vs. just a wall. There's dozens of ways to do it proper. One is to put in anchors on the fill side. Google it.

Actually the infill doesn't go up to the wall.

[IMHO]

Both sides should be rendered, and the whole thing should be coated in at least primer.

If you plan on landfill, it is wise to let the whole thing harden for several months before adding dirt - the longer the better.

If you're going to backfill, posts at 2.0-2.5M spacing should hold 1M of dirt. If not backfilling, post spacing can maybe go out to 3.0-3.5M. 4M is really pushing it.

Make sure the posts and beams stay boxed for at least 8 weeks so they cure properly. When doing fences may contractors just don't have enough wood, so will compromise curing time so they can keep the job moving.

Make sure the main lower beam is at least 60cm high, and is *underground*, not on top of it, and make sure every post has a footing at least 1.5M into the ground with a 1Mx1Mx30cm footing otherwise you'll get a topple-over wall like Transam's pic. Lower beam should use at least 6x 12mm-16mm rebars, tied every 8" with 6mm steel.

Posts should use 4x 9-12mm rebar, tied every 8" with 6mm rebar, and make sure the steel used is Mor Or Gor, not the cheap junk sold at smaller depots. Posts should be at least 6" square before rendering. The posts should have 6mm rebar poking 50cm into the space between blocks at least every 2 courses.

The head beam should be the same width as the posts, and use 4x9mm rebar, tied every 8" with 4mm steel.

The basic concepts for a wall that doesn't fall over is that posts are not too far apart, that it's almost as high underground as it is above ground, that posts are properly tied together with two beams, and the block are properly attached to the posts.

And that the whole thing cured slowly so it's strong.

Edited September 2, 2013 by IMHO

[Khun Jean]

... and make sure the steel used is Mor Or Gor, not the cheap junk sold at smaller depots.

Is there a way to test the steel quality.

[IMHO]

... and make sure the steel used is Mor Or Gor, not the cheap junk sold at smaller depots.

Is there a way to test the steel quality.

If you're not sure what you're getting, weight is usually the best way to check - the cheap stuff might be the right size, but it won't weigh nearly as much.

Easiest is simply to buy from a reputable dealer like Cementhai/HomeMart or Thai Watsadu (make sure you specify Mor Or Gor) or from GlobalHouse (they only sell Mor Or Gor)...

[luudee]

One mistake that we did, is not to make expansion gaps every 2-4 meters.

My wall is cracking badly ,and I am told it's because the concrete is "moving"

and when it expands (from the heat) it has no way to go ...

rudi

[IMHO]

One mistake that we did, is not to make expansion gaps every 2-4 meters.

My wall is cracking badly ,and I am told it's because the concrete is "moving"

and when it expands (from the heat) it has no way to go ...

rudi

Cement and Steel expand and contract at the exact same rate - which is what makes it such an effective and strong combination.

Hard to say why your wall is cracking without seeing it, but primary suspects would be improper cement curing, or inadequate foundations.

[transam]

One mistake that we did, is not to make expansion gaps every 2-4 meters.

My wall is cracking badly ,and I am told it's because the concrete is "moving"

and when it expands (from the heat) it has no way to go ...

rudi

Cement and Steel expand and contract at the exact same rate - which is what makes it such an effective and strong combination.

Hard to say why your wall is cracking without seeing it, but primary suspects would be improper cement curing, or inadequate foundations.

Yep,foundation pads not big enough and/or set on non settled or virgin ground.

[luudee]

One mistake that we did, is not to make expansion gaps every 2-4 meters.

My wall is cracking badly ,and I am told it's because the concrete is "moving"

and when it expands (from the heat) it has no way to go ...

rudi

Cement and Steel expand and contract at the exact same rate - which is what makes it such an effective and strong combination.

Hard to say why your wall is cracking without seeing it, but primary suspects would be improper cement curing, or inadequate foundations.

Hmm, I am not an expert at all, but that's what I was told by others ...

I'm pretty sure the footing was done well. It was dug up extra deep and it was all "old ground".

The feet where good size in my opinion ...

I was told bridges utilize gaps as well, because the concrete moves ...

And the same principle applies here as well.

So if I have two poles with solid footing and a wall between those poles,

when the wall expands, it would have to push the poles out, right ?

Which I guess is not possible, and the wall cracks ...

Again, I am not an expert, just guessing here.

rudi

[IMHO]

One mistake that we did, is not to make expansion gaps every 2-4 meters.

My wall is cracking badly ,and I am told it's because the concrete is "moving"

and when it expands (from the heat) it has no way to go ...

rudi

Cement and Steel expand and contract at the exact same rate - which is what makes it such an effective and strong combination.

Hard to say why your wall is cracking without seeing it, but primary suspects would be improper cement curing, or inadequate foundations.

Hmm, I am not an expert at all, but that's what I was told by others ...

I'm pretty sure the footing was done well. It was dug up extra deep and it was all "old ground".

The feet where good size in my opinion ...

I was told bridges utilize gaps as well, because the concrete moves ...

And the same principle applies here as well.

So if I have two poles with solid footing and a wall between those poles,

when the wall expands, it would have to push the poles out, right ?

Which I guess is not possible, and the wall cracks ...

Again, I am not an expert, just guessing here.

rudi

Go have a look at the fence around the nearest govt building (school, amphur office, DLT etc) - in most cases that have cement + block walls hundreds of meters long, with no expansion joints, and no cracks or falling over

If your foundations were well implemented, it probably because of inadequate curing - read the bold text in my first reply

[Soutpeel]

... and make sure the steel used is Mor Or Gor, not the cheap junk sold at smaller depots.

Is there a way to test the steel quality.

Yes there are plenty of ways to test the quality of steel...but weight ain't one of them

But of course before you get to testing the quality of the steel, need to decide what quality you want