Shopping for cement blocks (called hollow block) in the Philippines is certainly not a top pick adventure story but anyway, perhaps someone will benefit from our experiences. Really, this is one chapter in the building of our Philippine house in Tigbauan, Iloilo.
We’re fencing the lot we bought in Tigbauan with a cement block wall. Why? To keep out roaming carabaos, dogs, ducks, chickens and goats, to assert our property rights, to keep in our dogs and to keep out uninvited guests or intruders, and because we will be filling the lot to raise its level so that our house won’t flood during typhoons. Since we’ll be putting in up to one meter of fill, a wall is needed to retain the fill.
Our lot was surveyed three times. The first was by the seller. All the “monuments” were missing from that survey. We asked the seller to resurvey the property before we bought it. They put in bamboo monuments. We had them come back and put in concrete monuments. These were the round precast concrete monuments about 4″ in diameter and 18″ long which are sold in building supply stores. Because the new monuments were not set in concrete, by the time we were ready to build our fence, some of the monuments were missing or displaced so we had to have it surveyed again, this time setting the monuments in concrete. After the batter boards and lines (using 16 gauge tie wire) for the fence layout, the monuments were removed again when the column footers were dug.
The above photo shows our lot as we bought it. These is normal wet season season flooding conditions in Philippine rice growing lands. The soils are very heavy clay and tend to retain rain water — perfect for growing rice but not really ideal for residential development and especially not ideal for septic systems.
Many expats are willing and able to get personally involved in construction projects; hiring, supervising and firing local employees, shopping and bargaining for materials, getting permits and all the rest. Bob did not feel comfortable with doing that so we hired an architect to develop the plans and to oversee the project. Plans? Yes, a building permit is required for the wall and to get a permit plans are needed. We also wanted plans and specification to ensure that the wall was actually built the way we wanted it to be built. We heard lots of stories about poor quality block. We told the architect that we wanted top quality block and that we wanted to approve the quality of the block in advance of its purchase and delivery. That proved to be more difficult than we thought.
Our architect knew of a major supplier of block to the Iloilo area so we piled into his car to visit the Damasco block plant in Pavia, Iloilo. The firm had a small storefront in “downtown” Pavia, so that was our first stop. They showed us their standard 4″ block. I really don’t have much experience with block and don’t know proper methodology or equipment for testing it, but here’s what I did. I brought along my 20 oz. Estwing hammer. My theory was that rapping a block would at least determine if it would easily crumble. The ring of hard concrete would also contrast with the dull sound of a over-sandy block.
It was immediately clear that the block we were looking at was weak. When hit it, there was a very dull thud sound, not the ring of hard concrete. It was easy to tap a hole in the block. Another quick test, one which shows how low the bar for blocks in the Philippines is set, is to grasp the block with your hand and push on a protruding corner of the block. With poor block the corner will crumble away.
Anyway, this is a standard block used in most local building projects. When used in a house or wall they are said to be not really structural. The block is are reinforced with rebar, filled with wet concrete and then parged with concrete on both sides. So, the explanation is that the strength of the individual block is not that important. These blocks are made to sell for little money. The block I ruined with my Estwing cost P9.75. Doubtless, this price would be reduced with discounts. Hence the block is mostly sand with not much concrete. I have seen worse. I went to one block plant that made blocks so weak you could crush them with your shoe.
We do not accept the idea that weak block is OK. Generally, 4″ block is used. The cavity in 4″ block is small. The filling of the block with concrete is often so haphazard that the idea that it will add much structural strength is wishful thinking. Very often concrete is not used. Mortar is used to set the block and so it’s much easier to fill the cavities with mortar than to keep both mortar and concrete mixed and ready. We are increasingly dubious that the quality of hollow block is unimportant. The shear strength of wall is a critical factor in earthquake survival. See our post /earthquake-philippines-design-right/
To continue with our block shopping, since our fence was not to be parged, we wanted a less crumbly block. The worker at the storefront sent us back to the yard where the blocks are made. Damasco’s was an impressively big operation. The owner was very articulate about global warming, the Greenland ice cap and Al Gore. He said the standard block were manufactured at seventy blocks per bag of concrete. (A bag of concrete costs about P200.) He said the strength of these standard blocks is 300 PSI. He showed us some well-cured 700 PSI block. Forty blocks are made with one bag of concrete. I did the “Estwing test” on these. These were much better, but still not comparable to block I had handled in the U.S. The owner said he would custom make 700 PSI block for us, but the cost quoted to us is just about double that of the 300 PSI block. Is it any wonder that most use the cheaper block! Using better block would add about $1,000 to our fence project cost. Also the better block is custom made. The special order takes three weeks to produce.
After looking at and testing dozens of blocks, I decided to use the Damasco 6″ standard block. The quality of Damasco’s standard 6″ block seems better than the competition. Why 6″? The price is only P1 more than the 4″. The big advantage of 6″ block is that the cavity is much bigger than that of 4″ block so the extra concrete fill will make a stronger wall. We are paying P13 per 6″ hollow block delivered to our Tigbauan building site. We also bought 4″ block from Damasco but were no so impressed with it. Keep in mind that we probably could have bought local 4″ block in Tigbauan for P7 each and we would have used considerably less concrete to fill them.
We were recently in Manila. There was a minor construction project going on near the Manila Pavilion Hotel with a pile of 4″ hollow block near the sidewalk. I could not resist going over to examine the block. It was immediately obvious that it was better block than that available in Iloilo. It really had a significant cement content.
***OUR RECOMMENDATION is that of many other expats. Don’t buy poor local block. Buy a block making machine for about P20,000 to P30,000. You can sell it when you are done. Make it a part of the purchase that the seller will train your crew to use the machine and make block. Hire two or three workers. Maybe you won’t save money but you’ll get far superior block and a better, stronger fence and house. We also suggest that only 6″ block be used for reasons given above.*** Also keep perspective. The cost of hollow block, good or bad, in a surprisingly small percentage of the cost of building a house. Your paint will probably cost more. The extra cost of using good block is not worth obsessing over.
We also looked at 36″ x 18″ precast tiles for our well at Damasco. We got to see them being made. The quality seemed excellent, however there probably is a well digger in your area who has forms and can make well tile on-site. That will probably save you money. The story of digging our water well.
Read all about our Philippine House building Project at http://myphilippinelife.com/building-our-philippine-house-index/