Supervising Footing Construction

Watching Concrete Dry (Literally)

Standing at a construction site in 35-degree heat watching workers mix cement sucks. But you know what sucks more? Your house sinking 2 years later because the footing was built on mud.

Spread footings look simple. Dig hole. Put steel. Pour concrete. But there are about 50 ways to mess this up.

1. Before they dig

Walk the site. The plans say “Column C4 goes here” but is there a giant boulder there? Or a septic tank from 1990? Check the layout. Spray paint the ground yourself if you have to.

Soil check: I can’t stress this enough. If the soil looks like chocolate mousse? Stop. Don’t pour on top of it. Dig deeper or call your engineer. If you build on soft soil, no amount of steel will save you.

2. The Dig

Watch the depth. Workers get tired. “Sir, 90cm is close enough to 1 meter.” No it’s not. Make a stick with a line at 1 meter. Check every hole. If they dug 90cm, they dig 10cm more. Even if they complain.

3. The Steel (Hidden Mistakes)

Once the concrete is poured, you can’t see the rebar. So you have to check it before.

Common cheats:

• Wrong size: Using 16mm instead of 20mm. (Hard to tell by eye, use a caliper).
• Spacing: “200mm spacing” becomes 250mm when you’re not looking.
• The “Cover”: This is huge. The steel needs to be 75mm away from the dirt. Workers will use a stone or a piece of wood to prop it up. Don’t let them use wood (termite food). Use a concrete spacer (“dobie”). cost: 2 pesos.

4. The Pour

This is the main event. If the concrete is too watery, it’s weak. If it’s too dry, you get “honeycombs” (holes).

The Slump Test Make them do it. Flip the cone. Measure the slump. If they say “Boss, we don’t have a cone”… buy one. It’s cheap.

Vibration They need to vibrate the concrete to get air bubbles out. But if they vibrate too much, the rocks sink to the bottom. It’s an art. Watch them closely.

5. Don’t rush

Philippine weather is hot. Concrete dries fast. But you need to keep it wet (“curing”). Cover it with wet sacks. Keep it wet for 7 days. If it dries too fast, it cracks. Workers will want to strip the forms the next morning. Tell them to wait.

Bottom line

You don’t need to be an engineer. You just need to be annoying. Ask questions. Measure things. Make them nervous. If they know you’re watching, they’ll do it right.

(mostly).