FOUNDATIONS FOR A NEW HOME

Foundations for a new home are built on top of footings previously poured. The foundation walls will support the structure above (usually wood frame but they structure can be brick or stone, or more concrete). The accuracy of the foundation walls is predicated on the accuracy of the footings. If the surveyors pinned out corners are still visible through the staked down PVC piping then we can sight the corners very accurately. Once the footings have been partially stripped we can begin standing up ply wood and making forms. Because of the care taken to trowel the footing off accurately, standing up the walls is a quick and efficient process.

We usually use 3/4″ plywood for the form materials. When we strip the poured walls we can clean off the plywood and use it for sub floors on top of TJI’s (with our Structural Engineer’s permission of course). This action has two benefits

• we reuse the plywood for sub floors thereby saving money on sub floor plywood
• the concrete walls are straighter than if we had used 5/8″ plywood

We use 8″ snap ties and form clips to hold the walls together during the pour. This gives us an 8″ foundation wall. We snap  off the ties once we have stripped the plywood.

FORMING THE WALL

Once we have one side of the walls formed and supported, we install a “pour strip”. The pour strip is a piece of 1 1/2″ x 1″ material that we run horizontally  at the top of the form at the correct elevation. This “pour strip” acts as a guide for the concrete placer to trowel off  the top of the wall. We can now install re-inforcing steel. The vertical wet dowels placed in the footings provide a strong point to tie in the vertical bars in the walls and the horizontal bars tie in to the verticals. Thus creating a rigid mesh which is tied in every direction. Once this is all complete and before we close up the second side we call for all the required inspections. Firstly Structural Engineer and Building Inspector. Before we are finished we make sure the forms are square, vertical and that walls are in line and properly braced to avoid any collapse.

One side up

Extra mesh

 POURING THE FOUNDATION WALLS

Depending on the height of the walls the pouring of the walls can be critical. On our pour we have some walls 14 feet high. The placer comes with a five man crew and a vibrator capable of reaching down into the foundation right to the footing. We pour in four foot lifts vibrating all the way down. This means we have to circle the forms three times and vibrate every time right to the footing. This will ensure the concrete is homogeneous and will have the minimum amount of honey comb or air pockets, in the finished concrete. Once the walls are trowelled off we place anchor bolts by hand into the top of the wall.

STRIPPING THE WALLS

Generally we strip the foundations walls within a few days, but they can be stripped the next day. Concrete sets up quickly but does not come up to full strength for 30 days. Next step Waterproofing.