Our biggest Philippine house building blunders. We don’t want to present our project as a paragon of perfection, so here we show what went wrong during our Philippine house construction project and why, in the hope that others can learn from our mistakes. Most of these photos also appear in other sections of the site.
This photo shows the top of a 15cm column trying to accommodate eight 16mm rebar from the roof beams and four 12mm rebar from the column. There is practically no room for concrete. I ended up welding this tangle of rebar in the hope of gaining some strength from the rebar even if the concrete was minimal. The post should have been sized by the engineers to be large enough to properly accommodate the rebar. I told the engineer I wanted to demolish this column. The engineer talked me out of it, however it should have been demolished and replaced with a larger column.
The engineers left out a support column needed to support a beam which they also left out. One of the workers looked at the plans and saw the problem early on. The engineers left out support for one end of a main roof truss. We could not build in that defect, so we had to demolish a just constructed wall and wall footer (shown above) to allow us to pour a footer for the added column. The concrete in the demolished footer was satisfyingly strong and resistant to demolition.
Workers laid block right up to rebar cage for columns, leaving inadequate room for the concrete portion of the column. The block (which was filled with concrete) had to be cut back throughout the structure — a big waste of time.
This shows a rebar cage for the roof beam. The splicing was done incorrectly. No splicing plan was included with our drawings so the workers followed their own ideas which proved to be wrong. See /our-philippine-house-project-rebar-splicing/ for all the gory details. This particular rebar cage was redone three times before it was done correctly. I don’t blame the workers. In our opinion, a splicing plan should have been provided by the engineers.
This column was demolished and replaced. The concrete was too stony and dry, perhaps because I went too far in insisting that not too much water be added to the concrete. While almost everything one reads about concrete warn that water is the enemy of concrete strength, as I learned, concrete should be wetter in hot conditions. See the Portland Cement Association’s “Hot Weather Concreting” at http://www.cement.org/tech/basics_hot_weather.asp Many of the suggestions can only provoke a smile in the provincial Philippine situation, such as using liquid nitrogen cooled aggregates or cold water in mixing concrete, the suggestions about the importance of wetting forms and using a somewhat wetter mix make sense. We also keep concrete beams wet for a few days. It takes concrete thirty days to cure.
This defect was caused by my crew over-using the concrete vibrator. The water and concrete slurry ran out of the bottom of the form, leaving behind the aggregate. The crew tried to hide this from me by covering it with mortar. I raked it out immediately.
The welders were working at making the windows at the same time the window openings were being made. Not great communication or oversight — including my own!
This is the aftermath of one of the more discouraging days. The plans call for 12mm vertical rebar in the interior hollow block partition walls. Since our walls are over ten feet high, this is especially important. By the time I noticed (the foreman never noticed) that the crew had switched from using 12mm bars to the weaker 10mm bars, several courses of block had been laid. I mulled this over and decided that I was not comfortable with the use of the 10mm bar and had all the work containing it demolished. This amounted to three or four courses of block throughout the interior. I could not get a satisfactory explanation of why the crew switched from 12mm to 10mm. So we are paying for the original labor and materials , the demolition and new labor, block, cement and aggregate. If I was not on-site, I never would have known about this problem.
It was amazing and a bit depressing to see how easy it is to demolish these walls with a hammer. The 4″ block is weak, the mortar is weak. If I was ever to build another house, I would use six inch block exclusively. Don’t depend on 4″ walls for shear strength to resist lateral forces in an earthquake.
This shows a column rebar cage way off the center of the footer. Imagine sitting on the edge of your chair. It’s tippy. When this column is loaded, the tendency is for the footer to sag or tip. The column was poured off center because the crew did not want to enlarge the footer excavation so that the column could be centered on the footer. This thick concrete footer had to be broken up and repoured.
The engineers specified roof trusses which could span the house without supports — but why? A simpler truss system using interior walls as mid-span support could have cost less.
Our workers did not understand the need to keep footer rebar positioned well up in the footer concrete rather than laying the rebar on the ground and pouring the footer over it. We did not have any of the rebar chairs shown above so we used larger stones to raise the footer rebar above the ground before we poured. Having the rebar on the ground in the bottom of the footer is a serious defect.
How are such concrete problems repaired? We considered using epoxy but John Thede Joergensen’s suggestions seem right:
“I would use a thin plaster of fine sand and cement. 1:3 and wet, slam it on layer by layer thin layers at the time.The slamming is like blowing it on, and leave the sandcorn in the thin plaster, but like its vibrated in. It takes time and a good masonry hand to do it, but it is the same technique used when a concrete bridge is damaged by a truck, and the reinforcement is open. Then thin strong concrete is pumped and sprayed on to it layer by layer until its built up again. I don’t know if you can get the tool I think of there. I will find a picture and attached here. The floating plaster is balanced on the blade,and with a swing slammed on the surface. Practice on a plate first. Build it up, and let it dry in between till a point where you can “cut” remains away with the tool. Then use a sponge to make the surface smooth.”
Read all about our Philippine House building Project at /building-our-philippine-house-index/