BOARD-FORMED CONCRETE

“Board-formed Concrete” is a process of patterning concrete that leaves a wood grain and joint line image on the finished face of the concrete. This method of construction is being used more frequently as concrete is becoming well-suited as a finished material in modern building designs. By having the wood joints and grain imprinted on the finish surface, it visually softens and warms concrete’s hard appearance. 

Another one of our unique projects is coming to an end where one of the main exterior features on the home is a very tall and long concrete wall that encloses the garage. In order to make this feature truly appealing and more than just a concrete wall, the architect chose board-formed concrete method. When doing a wall such as this there are several important factors that affect the finished product, such as rejecting boards with defects to prevent any blemishes from showing up in the finished product and using brand new, hand selected lumber to make sure all lines and edges are straight.  Do this will ensure a cleaner, crisp out-come.

The concrete wall on this project is approx. 14’ tall and close to 30’ in length, with a space in the corner for a butt glazed steel frame window. The window was intentionally aligned with the board coursings to create clean and intentional lines. The wall stands taller than the roof and ties into both the structure of the roof and the roofing materials. The roof’s structural members were set into imbed plates that were set in the concrete wall as it was being formed, so that the finished product has no exposed plates or fasteners.

Forming for these walls can be very tedious since the amount of pressure of the wet concrete is truly something to consider. In order to combat the immense pressure there are a few things that are key to a successful pour.  Using massive amounts of bracing on the forms, to withstand the force of the wet concrete is key to not losing the wall.  Also by mixing the concrete on the dry side and adding it very slowly and deliberately to prevent the formwork from blowing out, losing the whole operation.  When pouring it is impossible to see if the concrete face will be smooth without blemishes or air pockets until the form boards are removed.   By extensively hitting the sides of the formwork, it helps to settle the concrete and knock out any air pockets. It is quite difficult to patch or touch up any voids or pockets that appear once the forms are removed.

There’s one chance and one chance only to get walls like this to come out right. If it fails it is a total do over or a long intensive patch job. It’s close to impossible to get one of these to come out perfect, but this one came out pretty close. 

 

BOARD-FORMED CONCRETE PROCESS

Foundation

FSB recently poured the cement for the foundation on a current project. The design of the foundation is to help minimize the movement in Austin’s Clay soils. Since clay expands and contracts most modern foundations are designed to rest in deep piers with a void or air space under the actual concrete slab. This is accomplished by drilling and pouring deep, with bell bottomed piers for the slab to rest on. The interior of the slab is then voided. This creates the desired air space or void for the soil to move up and down and never come in contact with the underside of the slab.

One thing that is difficult for such a large slab is that it all has to poured at the same time. In this case, it took 15 men and approx. 14 hours from start to finish to get this one done. This slab also required a very large and long pump truck with a serious boom on it. All went like clockwork on this pour. Our thanks to our concrete man Dan for pulling it off on time in spite of the rain we’ve had almost every day in the month of May.