Saturday, August 11, 2007

Going Vertical

I got to witness the first big concrete pour on Thursday--very impressive. There must have been 9 or 10 concrete trucks showing up every 20 minutes or so, for over 3 hours of pouring.

It was hot and it was humid, and the crew worked their butts off. It was also somewhat humbling to find out it took a solid week to set up the forms to accomodate the T-Mass insulation, the wire reinforcing mesh, etc. Concrete guys probably like corners less than any other building trade, because it's a beast to get every form perfectly square with all the zigs and zags the walls make. Sorry guys!
The construction economies I had expected ("I'll just pour the T-mass walls and I won't have to insulate, paint or install vapor barriers" would seem to have disappeared. Aesthetically, t-mass was still the right way to go, and I still expect to save money heating and cooling the place due to the tightness and the thermal mass effect of the concrete.

Above is a panoramic photo taken 2 days after the pour, comprised of 5-6 regular shots, so don't be thrown by the bowed walls that are artifacts of the stitching-together process. There were some glitches with the aggregate hanging up and creating some voids, which is an issue with the above-ground parts and particularly those on the inside, so we'll have to come up with a touch-up approach that looks authentic and not "appliqué" – my architect's personal bête noir.


Dan N. said...

I just stumbled across your blog looking for t-mass experiences. I'm a concrete contractor in central Illinois and was considering this method for my own modern style house along with stone form liners.

You may have the "honeycomb" issue already solved, but just in case we use a product called All-Patch light. Really matches cured concrete very well. We get it from our local construction supply house.

I have a question for you if you don't mind - how hard was integrating all the various systems with the t-mass? e.g. electrical, plumbing, HVAC, etc?

Looks great!

Don Chartier said...

Dan, thanks for the tip on All-Patch--I'll look into it.

As for integrating the other systems, we're still in process. The electrical took a bit of coordination between the GC, the concrete guy and the electrician. Same with the plumbing. Obviously, once it's poured, you'll have difficulty changing your mind. We haven't gotten very far with the other systems, so it's hard to say.

Looking back, the form-setting took a fair amount of time because of the number of corners, and the effort required to locate the insulation panels and the wire mesh we used for reinforcement. I think the sandwich was 4" concrete (inside), 3" insulation, 3" concrete (outside). You want to have the thicker concrete wall on the inside to get a better thermal mass effect. The 3" concrete might be thin enough to cause the honeycombing, given that the mesh has to fit in there, and the aggregate seemed to hang up in it. You might consider a 5-3-4 or a 4-4-4 configuration, depending on your forms.

Good luck!