Building our house in the Philippines. All about putting up hollow block walls. We started building our walls as soon as the footers were in and at the same time as the columns were going up. Read about hollow block HERE, columns and beams HERE and rebar splicing HERE. Correct rebar splicing is just as important in the hollow block walls as it is the the columns and beams. Properly spliced rebar can tie your building together. Improper splices cost just the same and weaken the building.
Our wall footers were less sturdy than the column footers, but still hefty. The base of the wall footers are 80cm (2.6′) below grade. The concrete footer is 25cm (10″) thick and 40cm wide (1.3′). The footer is reinforced with four 12mm deformed bar (rebar). The walls had 10mm rebar horizontally every three courses and 12mm rebar vertically every 60cm (2′)
The photo gives an unusual perspective on the footer and wall. Because the engineers left out a porch column, we had to demolish part of an already completed footer and wall to make way for the added column. This photo shows the footer with the two 12mm rebar and the hollow block wall above. Demolishing the short section of the footer proved to quite difficult, perhaps a sign that the concrete quality is fairly good.
With some help from El Nino we had perfect construction weather. We did not have any significant rain between October 2009 until the roof was on in mid-2010. This has was terrible for farmers, but good for us. One continuing worry about the dry weather was that our well would run dry. We used so much water for making concrete, cleaning tools and equipment, watering plants, and for our crew’s personal needs — washing, laundry and so forth. We had the redug deeper in 2009. See /digging-water-well-tigbauan-philippines/
Once you receive delivery of your hollow block, you must constantly keep them wet. If they dry out they lose strength and eventually crumble back into the sand they were made from. 2-16-10. Day 26 of project.
Above. While this is a nice action shot showing a column being poured and vibrated, it also shows a serious problem. This is a corner column. The building should be well tied together at the corners. The rebar should sweep around the corner securely tying together the column and the walls. The red arrow points to the very short length of rebar protruding from the columns. The intent is that these stubs will be spliced to the horizontal 10mm rebar in the hollow block walls. However this splice is far to short and too close to the corner to provide a meaningful tie.
This is my crude drawing showing how the rebar should sweep around the corner, helping to tie the building together. It would be ideal if the rebar could extend to its full length or at least until a window or door opening intervenes. Of course there are practical problems in installing and working around such webs of rebar. This drawing is based on concepts in the highly recommended book “Peace of Mind in Earthquake Country” You generally can buy it used for about a dollar plus shipping at ABE books. Our plans provided no guidance on rebar splicing. Insist that yours do.
Also, if you have large windows, add one or two additional vertical rebar in the block cores on each side of each window opening. A large percentage of structural failures occur around door and window openings.
First the exterior walls went up. We used decent quality 6″ hollow block for the exterior walls. We very much regret that we did not use 6″ block for the interior walls as well. It would have given the house additional rigidity or shear strength so that it could better hold together rather than break apart in an earthquake. We did not use it because Bob thought it might reduce room sizes.
It’s very important that the hollow block cores be filled with concrete NOT mortar. If mortar or concrete starts to set, throw it our. Don’t let the crew add more water and remix. This is going to be a very tough sell to the typical Filipino mason.