Good morning, I am making a small wall with these concrete blocks but am pretty ignorant. I've got the mortar already and in fact have already started but....which way do the blocks sit, hollow part up or down? What do I cap it with...do I need to cap it? And lastly, do I need to seal it with a layer of cement or stucco or paint to keep out moisture/water damage?

 

Thank you!

Hollow side up.

 

What are you building and how, how high do you plan to go, what support exists for the wall? Those blocks can be used as infill as long as they are supported at each end or by another face of blocks, but you can't go very high because they are so narrow.

 

Whether or not you cover them with a screed when finished depends on what you are building.

Awesome, thanks. I'm only going one block high...I'm just building a barrier wall trying to keep flood water out of my carport which happens a few times during the rainy season in the big downpours. I laid some yesterday and luckily did put them hollow side up but was thinking rain water is going to get in the hollow spaces now. They are so porous, will the weather destroy them? I don't care that much about the aesthetic, that's not a concern. I just don't want the water flowing over the carport which I want to use for storage.

In that case, I think if it was me, I might either fill the hollow part with concrete or cap the blocks with a row of something or other, just to keep water out. Those blocks are pretty sturdy so they are unlikely to be effected too much by weather. The key issue will be, what force of water will the blocks have to hold back, if it's a lot then I might infill them. If you wanted to get really sexy you could buy some waterproofing paint/liquid and coat them, but I doubt that's really necessary. Lastly, make sure the water can't find a way under the blocks/wall otherwise you'll have problems.

Being only one block high and non load bearing or retaining , nothing can really go wrong . Definetely use waterproofing that mixes with the mortar as well as on the blocks . If the concrete surface is very smooth ( unlikely in Thailand ) , rough it up a bit first .

Bondcrete or lockcrete depending on where you come from. Can be added to any plastering finish or just painted on to the raw block. Usually white like pva glue and dries clear and waterproof.

I doubt it would make any difference which way up the block was laid.

 

 

Thanks all. The water doesn't get that high as the carport is already raised a bit. Only has to hold back a couple inches at most so not a big issue. I've already laid some without mixing anything in to the mortar and def paying attention to getting a good bead down on the bottom and between the bricks. Can I go back over all the joints a second time with the mortar as if it were spackle/caulking to make sure it's water tight?

 

So some say I should invest in a waterproofing cover and some say not. Can we get a consensus? Will the bricks fall apart from getting wet?

Couldn't you of carry out drainage works. 

Just now, Kwasaki said:

Couldn't you of carry out drainage works. 

No, the whole place floods. The yard, the street, everything. It drains off quick enough... I suppose if I owned the house and had the money, I could raise the whole area a foot or so but it's a rental.

On 11/9/2022 at 9:43 AM, nigelforbes said:

Hollow side up.

 

Actually, exactly the opposite. Otherwise the mortar placed on the next layer drops inside the cavity, not much left over for bonding the connection.

 

If properly made and in double cladding with a cavity in-between, strengthened by inserting horizontally into the mortar a 3mm steel wire at each 2nd - 3rd layer, it can serve as a load bearing structure for the whole house. Then, no need for the usual concrete poles (sau)  - protruding the walls, disturbing the furniture placing inside. And no need for the horizontal beams poured into extensive wooden formwork suported by thousand of bamboo poles, thus saving a lot of money and lot of time.

 

2 minutes ago, Saanim said:

Actually, exactly the opposite. Otherwise the mortar placed on the next layer drops inside the cavity, not much left over for bonding the connection.

 

If properly made and in double cladding with a cavity in-between, strengthened by inserting horizontally into the mortar a 3mm steel wire at each 2nd - 3rd layer, it can serve as a load bearing structure for the whole house. Then, no need for the usual concrete poles (sau)  - protruding the walls, disturbing the furniture placing inside. And no need for the horizontal beams poured into extensive wooden formwork suported by thousand of bamboo poles, thus saving a lot of money and lot of time.

 

Actually, exactly not, he's only laying a single course and a single skin.

3 hours ago, nigelforbes said:

Actually, exactly not, he's only laying a single course and a single skin.

What I read: I am making a small wall.

Whether a single or double skin the wall is surely made from more blocks placing each above other.  In that case the hollow opening always downwards onto the mortar.   

On 11/9/2022 at 9:43 AM, nigelforbes said:

Hollow side up.

 

3 hours ago, Saanim said:

Actually, exactly the opposite. Otherwise the mortar placed on the next layer drops inside the cavity, not much left over for bonding the connection.

Saanim is 100% right. nigelforbes is giving you bad advice.

Sika has 25 gallon waterporoofing agent for around 700 bht

18 minutes ago, Saanim said:

What I read: I am making a small wall.

Whether a single or double skin the wall is surely made from more blocks placing each above other.  In that case the hollow opening always downwards onto the mortar.   

Which part of, "I'm only going one block high", did you not understand!

Just now, Pouatchee said:

 

Saanim is 100% right. nigelforbes is giving you bad advice.

Sika has 25 gallon waterporoofing agent for around 700 bht

Somebody else who didn't read the thread before posting.....oh well!

 

 

On 11/9/2022 at 12:35 PM, bamboozled said:

Will the bricks fall apart from getting wet?

No - many walls all over Thailand are built using this type of block and they (and the cement mortar/grout) do not fall apart when they get wet.

 

On 11/9/2022 at 9:50 AM, bamboozled said:

I'm only going one block high...I'm just building a barrier wall trying to keep flood water out of my carport

If you are concerned about water-proofing why not paint afterwards with roofing paint?

8 hours ago, Saanim said:

Actually, exactly the opposite. Otherwise the mortar placed on the next layer drops inside the cavity, not much left over for bonding the connection.

 

If properly made and in double cladding with a cavity in-between, strengthened by inserting horizontally into the mortar a 3mm steel wire at each 2nd - 3rd layer, it can serve as a load bearing structure for the whole house. Then, no need for the usual concrete poles (sau)  - protruding the walls, disturbing the furniture placing inside. And no need for the horizontal beams poured into extensive wooden formwork suported by thousand of bamboo poles, thus saving a lot of money and lot of time.

 

It's only one course in height so it doesn't mater which way up .

On 11/11/2022 at 1:26 PM, nigelforbes said:

Somebody else who didn't read the thread before posting.....oh well!

Ever hear the idiom: do it once do it right?

Putting the bricks upside down not only looks wrong but his bricks will also retain water when it rains and they will also be less strong with the crown facing upwards rather than downwards.

31 minutes ago, Pouatchee said:

Ever hear the idiom: do it once do it right?

Putting the bricks upside down not only looks wrong but his bricks will also retain water when it rains and they will also be less strong with the crown facing upwards rather than downwards.

Which is why I suggested he back fill them or put on a topping layer.

On 11/9/2022 at 12:35 PM, bamboozled said:

Thanks all. The water doesn't get that high as the carport is already raised a bit. Only has to hold back a couple inches at most so not a big issue. I've already laid some without mixing anything in to the mortar and def paying attention to getting a good bead down on the bottom and between the bricks. Can I go back over all the joints a second time with the mortar as if it were spackle/caulking to make sure it's water tight?

 

So some say I should invest in a waterproofing cover and some say not. Can we get a consensus? Will the bricks fall apart from getting wet?

No they will not fall apart, ever.

2 hours ago, nigelforbes said:

Which is why I suggested he back fill them or put on a topping layer.

Which he won't need to do if he does it right from the first time. Moreover, if he follows your advice and one day builds 2 layers up he will continue to do it the wrong way. Funny how some people find it so hard to gracefully admit they are wrong.

On 11/11/2022 at 1:06 PM, Saanim said:

What I read: I am making a small wall.

Whether a single or double skin the wall is surely made from more blocks placing each above other.  In that case the hollow opening always downwards onto the mortar.   

Keep reading subsequent posts and the coin will finally drop.

Hi all, thanks for the back and forth.... I've been away building walls and moving stuff. I have the holes up, right or wrong. Yes, only one layer high. I have a waterproof tarps for walls that later on down the road I might turn into something beefier but for now it will do as long as I secure it well (wind! Last night was the first time to experience that since building it and I see the room I've created is a big sail). It ain't pretty but it was pretty cheap. The tarp is on the outside of the blocks so they won't get rained into. I don't know that I need to bother capping it since I can't even see from the outside as it's covered by the tarp. All this is a work in progress so we'll see.

 

Now....back to moving stuff. Man, what a workout!

I was in Bangkok this week and walking around various soi's to get to the MRT. For whatever reason I kept stumbling across one block high retaining walls similar to what you described. I cam across three, all one block high, designed to hold back soil for plants........open side up! I'll post pictures when I feel better after contracting covid.

1 hour ago, nigelforbes said:

I was in Bangkok this week and walking around various soi's to get to the MRT. For whatever reason I kept stumbling across one block high retaining walls similar to what you described. I cam across three, all one block high, designed to hold back soil for plants........open side up! I'll post pictures when I feel better after contracting covid.

You need a one-block high wall around that infection!