Stemwalls and Rat Slabs - Part II

TIME FOR MUD!

So, helping me get the stem-walls completed and working the concrete during the pour, again, is Joe Strickland from Skyline Development and his crew, Bob and Nick.

In come the pump truck and the concrete truck:

The pour started with the front corner and slowly progressed around the house. The major issue with pouring concrete walls is the pressure that builds up at the corners. It's entirely a matter of hydraulic pressure and the corners will face the greatest loads. So the guys were incredibly careful when pouring the corners.

Here you can see a good view of the concrete pump filling the cavity in the ICF. There is both horizontal and vertical rebar within the cavity.

Once the stemwall pour was complete, we quickly finished preparing the crawlspace for the rat slab. The dirt had already been graded and the next step was to lay down a 6mil plastic barrier that would help limit moisture migration into and out of the slab.

 

While the guys were handling the rat slab, I started setting the various bolts. There were two types of bolts, hold downs, which needed to be set in a specific way so that they looped around the rebar in the stem-wall, and anchor bolts, which only needed to be set in the concrete, but without any special placement. Here you can see the guys finishing up the rat slab and you can see the anchor bolts set into the stemwall.

And the result is incredible. I now have a smooth rat slab, a strong stem-wall and I can begin working on the next phase of the project (rough framing).

Stemwalls and Rat Slabs - Part I

As you'll note, it's been over a month since the last post. I (naively) thought that the stem wall would go rather quickly. And, realistically this *could* have been the case.

But I had a few decisions to make, and once the decisions were made, I had to finish up the work to make it happen.

The big decision was around interior of the crawlspace, and whether I should insulate the floor of the crawlspace now and cover it with a thin layer of concrete. (This thin layer of concrete is called a "rat slab" because it's not thick enough to be structural, it's just thick enough to keep rodents from tunneling up through it.)

The advantage of pouring the rat slab at the same time as the stemwall, is that I wouldn't have to have the pump truck come out a second time, and the pump truck costs roughly $600 per visit. The disadvantage is that I haven't picked out the type of insulation I want to use to insulate the floor. Normally, when insulating a floor like this, you place the insulation underneath the concrete (see above).

In the end, I decided I would go ahead and pour a rat slab when I pour the stemwall, but I wouldn't insulate underneath. The reason I think this will work is that I'll simply place the foam insulation above the rat slab and then lay down a plywood subfloor above to protect the foam.

Normally, this wouldn't work very well, but because the crawlspace will not be heavily used, the plywood should do a decent enough job of distributing the load.

Now that I've made the decision to pour the rat slab, I also had to figure out how I would support the house during the pour. Currently the house is supported on the interior with eight steel posts sitting on 1/4" steel plate. Unfortunately these supports are on the interior where the rat slab needs to be poured.

So I consulted with my architect and confirmed that I could support the beams with some of the left-over 2" pin pile pipes. I then used a laser level to cut the various pipes to the perfect length to bring the house to level.

Above, you can see the pipes after they were cut and welded to 1/4 plates on the bottom to help distribute the load. I also took the precaution of filling the pipes with concrete so they wouldn't be hollow, on the assumption that this would help strengthen the pipes.

I then jacked up the house a little bit, positioned the pipes underneath the beams and welded the pipes to the beams. I then welded the pipes to the vertical rebar, so that they would be supported laterally and keep the house from moving. And as you can see in the picture below, the posts were positioned within the stem-wall.

So I used a relatively "cheap" rotating laser when performing the measurements. According to the laser, the footings were sloped by about an inch over the length of the house. That didn't seem extreme to me, but when Joe the contractor came out, he was surprised. He was very exacting when he leveled the footings, and used his *very* expensive and *very* accurate laser. As soon as he said this, my shoulders slumped because I realised my laser was likely off and I had cut the pipes to the wrong lengths.

This led to him using his really awesome laser to help me figure out how far off each of the beams was from level. I then had to figure out how much I would need to shim each beam in order to bring the beams and house to perfectly level. This took about two hours, but I can't complain too much, because now the house should be level within 1/8". And because the foundation is sitting on pin piles, there will be virtually no settling. It is a little surreal to think that 50 years from now, this house will still be level within 1/4".

Now comes the ICF! ICF stands for Insulated Concrete Forms. The idea is that you used thick Styrofoam for the forms, and then after you fill the forms with concrete and the concrete cures, you leave the forms in place. The Styrofoam then acts as insulation. An added bonus is that they are pretty quick to setup as well!

The easiest way to think of ICF, is as large, hollow LEGO blocks. You stack them up and overlap the edges for strength.

Up next, the concrete trucks show up again and it'll be time for mud!

Trees be gone

From the footing pour, you might remember that the trees out front were a pain in the ass.

Well, no more!

I had an arborist come and remove the trees. Because the trees were on a city owned planting strip, I had to have the work approved by the city arborist and then utilize a city approved contractor. But luckily, due to the time of year and the slow economy, it was relatively cheap.

I had them leave the firewood, which I'll give to my neighbors.

Time for MUD!

(Mud is slang for concrete.)

When I last left off, I had decided to bring in a contractor to get the foundation completed and get the house framed up. Well I sought out bids from roughly 10 contractors and in the end, ended up going with one who had previously worked with a friend on his renovation. I chose Joe Strickland with Skyline Development. Great guy, intelligent, respects my budget and has tons of ideas for making the whole build faster and more efficient.

Onto the foundation!

The first thing to be done was to setup the forms and tie the rebar for the footing. This wasn't trivial as it would require a little excavation cleanup and then leveling the forms, reinforcing them and finally getting the rebar cut and in place. Joe and his son Bob, did a terrific job.

The inside form is made from 2x8s and the outside is a plastic drain / form called Form-A-Drain. The idea is that it will be used as a forms and then left in place as the perimeter drains, instead of having to install a 4" perforated pipe. I chose it because it seemed like it would make the footing easier to form and also because I had limited space for excavation and it would help with that. In the end, it was a pain in the ass to work with, and I'm not sure I would do it again.

To place the concrete, a pump truck was hired. The truck had a boom that would raise over the house, so that it could place the concrete around the entire perimeter without a lot of hassle. I couldn't believe how much easier this made the job, it was terrific.

In total, 12 yards of concrete were ordered, split into two trucks, one truck had 8 yards, the second truck had 4 yards. This is the second truck arriving.

 The process is simple actually, the concrete truck backs up to the pump truck and unloads the concrete into the hopper.

This picture hopefully shows the scale of the trucks, they are both quite large. Also, I was happy with the amount of use the curb cut took. I'm happy to say it fared perfectly well, no cracks, no damage.

Here, you can see the boom as it reaches over the house and pumps the concrete into the form at the back of the house. You can also see Joe and Bob working the concrete into the forms and smoothing it out.

You can tell from Joe's smile that this is the completion of the pour. I estimated that we would need 11.6 yards of concrete and so I ordered 12 yards, just in case. It turns out we needed just that amount. It worked out perfectly, no waste.

One of the odd things I found during the demolution, was that someone had placed a horseshoe under one of the original concrete piers for the house. I assume it was placed there for good luck. I made sure to save it.

So now, with the new foundation poured; I placed the old original horseshoe into the footing, along with the handprints of those who will make this house a home.

My first theft....

So I met a plumber at the site this morning to discuss the side sewer connection. It was early and I was a little out of it.

But after a while, I realised that something looked "off". I looked around and realised that someone had been to the house and stolen the old cast-iron waste pipe and the left over pin pile pipes. (Edit: the pipe was left, I was merely oblivious to it.)

All told, this was the first theft at the house, for which I'm grateful. And they only stole the leftover material. They left the rebar alone, and they left the foundation forming material alone, but still.

WTF?

Starting the foundation

So this last weekend, I intended to get the foundation footing forms setup and ready to go. Good idea, but I don't think I understand how much time I will need to spend getting the forms setup, the rebar cut and in place and I certainly don't think I can do the concrete pour by myself.

So I did the next best thing, I stayed busy by prepping the rebar, getting it cut and bent.

So now that the rebar is ready, I think I am going to call around and find out how much a foundation contractor would charge me to come in, setup the forms and install the foundation. The concrete work seems really daunting to me, mostly becuse I really need the foundation to be square and level, and it's concrete, so you only get one chance to do it. If I mess up, it'll be too costly.

Pile Driving Completed!

It's been a while since my last post. Well, yes. The reason is that I managed to injure my back on the last day of pile driving. I only already finished 8 piles that day with only 7 left to go, and I was excited. At that point I was running the pile-driver on the interior piles in the house, and without much overhead clearance I was lifting the driver onto the pipes by hand (ie, no chain winch to assist me). And of course I arched my back picking it up and I could feel the muscle tear as it happened.

ouch

Now, as I said, I'm pretty burly, so I put on a back support and finished out the day in pretty wicked pain. But goddamnit, I wanted the piles finished, I didn't want it dragging out any longer. Plus, my month of pile-driver rental was almost up. So I persevered and completed the task.

Then I proceeded to do nothing for the next three weeks but sit around on muscle relaxers and hang out with my new best friend. Which brings me to the next picture!

This is Bubba. Bubba and I have lots in common. We like long walks in the park, jumping up on people, licking faces and peeing on things. You could say it's a match made in heaven. This day Bubba was hanging out while I measured how how much of the pipes to cut off.

To explain what I'm doing above....

This is the detail from the blueprints showing how the foundation will tie into the pin piles. You can see that once the piles are driven, you install a cap on top. This cap is then embedded into the foundation footing. So my next step is to use a rotating laser level, and then cut off the pipes so that they are all level and roughly 4" above the bottom of the concrete footing.

Here, I've already measured the pipes and cut them off. Now I need to clean up the excavation so that all of the pipes are 4" above the ground, and then install the caps.

Here the excavation is cleaned up and I'm ready to install the caps.

Remember how I said the caps were $20 dollars if I purchased them? Well, I can't stand to buy what I can easily build, so I fabricated them. I spent about 7 hours fabricating them, with material costs of roughly $5 per cap. So 48 caps * $15 per cap means I saved roughly $720 doing this myself. It also means I paid myself roughly $100 an hour to do this. That's roughly 4x times the wage I would get as commercial welder.

And the end result, the excavation is cleaned up, the caps are installed on the piles and I'm ready to begin setting up the forms for the foundation!