Good evening bloggers! Why waffles you might ask? Waffle slab foundation… that’s why! I will explain the details, but first let me return to the beginning of the story.
Brook’s parents stayed with us this weekend and her father has been a contractor for quite some time. After looking over the land and reviewing our final plans, he threw us a few bones.
The first word of advice was his suggestion for using a concrete beam supported foundation. For those who do not know how to build a supported slab foundation on an uneven soil surface… please review the diagram on the left. This diagram lays out the basics for our foundation plan…atleast the plan we had before Brook’s father explained what a “raft slab foundation” is. Using the raft slab method would allow us to use fill dirt below the slab without the need for tamping (Check out the video below to see what tamping is… the guy on the left is raking the fill dirt flat the the guy on the right is tamping it down).
“Tamping” is a process where you put a tamping machine on top of about 6″ of raked flat fill dirt that you have dug up from somewhere and dumped in your foundation wall. When you run this tamping machine over the dirt it compacts the 6″ of fill dirt down to 1″ of solid strong tamped dirt. You then repeat. We will need about 3 or 4 feet of tamped fill dirt for our foundation. This will take a LOT of fill dirt, renting a tamping machine, and a LONG time to tamp. Brook’s father’s suggestion is a welcomed way around this step.
You can see some examples of waffle slab foundations on your right and below. We would simply dig out ditches in the gravel and put rebar in them. This way when we pour the concrete for the slab these ditches will be filled under the slab and dry into concrete beams. These beams will rest on the foundation walls, and enable the slab to be completely supported without the need for tamping the fill dirt! I will be going over the idea of using a raft slab foundation with our engineer tomorrow in order to see if it is financially the best way to go given the extra cement and rebar we will need to use.
I had never heard of this method before and after a bit of research “Raft Foundations” or “Waffle Slabs” as they are sometimes called were developed in the 1980’s as a response to more traditional strip footing foundation failures in expansive clays. The raft foundation sits on top of the ground and has a lattice of steel reinforced concrete ribs and beams which provide support and stiffness. Because they do not require excavation and are specifically designed for each building they can be more robust, quicker to build and often less expensive than traditional foundations.” – ABBY
The second great idea Craig offered us was hills for our front yard instead of grading the entire thing flat. Right now our land slopes from the street down and to the right towards the back right corner of our lot. He suggested that we let the driveway slope to a flat grade for about 50′ and then have another slope down to another flat grade with a dip in the soil right in front of where our front porch will eventually be. This dip will allow our home to be higher then the lowest point in the front yard and will act as our drainage system where rainwater will flow be trapped in this dip and pass right around our foundation.
This grading plan will give us two flat levels for a front yard instead of one steep hill from the road down to a completely flat front yard. It will be cheaper, look better, and be simpler to go this route with the grading. You can see an extreme example of what we will be doing in the image on the right.
With all of this information floating around in our heads we decided to take it easy tonight and light up our new fire pit for the first time (thank you Megan for the fire pit!). Soleil and I ate our mac and cheese in the peaceful glow of the fire light under the stars.
Thanks for reading everyone and I hope your weekend was just as wonderful as ours! Goodnight.