Monday, November 25, 2013

Porch Footings

Digging the hole for front porch footings
 Today the excavator came back for the day. He backfilled around the garage slab and dug holes for the front and back porch piers.

You can see the precast piers standing in the background of the first photo. Then you can barely see the tops of them poking out of the ground in the second photo after they were placed precisely (within 1" each direction) as per the plan to support the wood framing that will go above it.

Three front porch footings installed
A porch (or a whole building, really) can have a floor system than is supported by piers and is over open air, rather than a full foundation wall enclosing a basement or crawlspace. This is much less expensive, and often done under exterior spaces, like decks.

On previous projects I've seen cardboard sono-tubes placed into the hole, and then filled with concrete and re-bar. ("poured in place", like the rest of the concrete work you've seen on this project). This was different, because the G.C. elected to use precast pier footings. They came delivered to the site yesterday and got installed and back-filled today. Quick and done!

Digging for the back porch pier footing
Placing the pier. Don't put it on Scott's foot!

Tuesday, November 19, 2013

Structural Primer

Today you will get a structural lesson. Does that sound boring and too math heavy? Well, it's not!

We could set this post to the tune of that old song: "The Knee Bone's Connected to the...Thigh Bone!"  Why? Because that's what it's like. Trusses or rafters bear on walls or beams; walls bear onto floor joists or joist beams; floor joists rest on girders; beams span openings in walls and they are supported by posts at each end, posts are point loads that need land onto beams or girders; and eventually it all comes down to the concrete footers that are underground.

First some definitions:
  • A Girder is a built-up beam that supports the main floor joists. It is in the crawlspace.You can probably see one in your basement, if it's unfinished.
  • Joists are the repetitive members that make up a floor or ceiling system. They can be supported by beams or walls or a combination of both.
  • Rafters are the repetitive members that make up a roof system (along with a ridge board or beam and possibly collar ties)
  • Beams span an opening (like over a door or window) and joists rest on top of them.
  • Joist Beams are in the same plane as the joists, but are built-up of more than one unit to accept a load that will be there.
  • Flush Beams are not dropped under what they support (like the girder) but rather are flush - or even- with the joists it supports. Hardware like joist hangers are needed for this to work.
  • Posts can be a couple of studs put together to support each end of a beam or such
  • Columns are round (as opposed to square edged posts) but are also vertical point-load carrying members.
  • Bearing Walls are when all the wall studs as a unit provide continuous support
  • Trusses are factory made (usually), can span long distances for floors or roofs, and bear outside wall to outside wall (so interior partitions are just dividers, not structural)
  • Engineered Lumber is made from cut wood, sawdust and glue and is much stronger (really!) and can span farther than 
  • Dimensional Lumber, which is 2x4s, 2x6s, 2x8s, 2x10s & 2x12s comes in a few different species, each with it's own strength and span characteristics.
Well - this is getting long, but stay with me. Here are some photos to put it all together:
Main Girder supports mid-span of floor joists. In this case it is a built-up engineered beam (Three LVLs put together) The framers are cutting a column to the correct height
Girder rests in beam pockets in the concrete wall and onto steel columns that bear onto interior concrete footings. Floor joists will run perpendicular the the girder and across the top of it out toward each side wall

Floor joists span from the foundation wall (sill plate, actually) to the main girder. Here is also a cantilever, which means the joists extend beyond the support  of the foundation wall over open air

Header with posts each end (over opening on the right) Flush beam (on top of wall by John's hand) Second floor joists will attach into that flush beam and run perpendicular to it
Long LVL beam will carry roof, floor and wall loads from above so the space can be open (ie. not have a wall there) This beam has posts at each end and mid-span, buried within the stud walls
Second floor joists - some running east-west landing on a bearing wall, some running north-south where Scott is installing more; also see headers over windows, because regardless of floor joist direction, that exterior wall will be carrying the main roof's load

It's just like Lincoln Logs! Well, maybe not... Did this help any of you understand a bit of how a house is framed? Now you should be able to look around your own house and figure out which walls (non-load bearing) can be changed easily to have a wider opening or a larger window- and which walls or beams are keeping the floor from collapsing when you dance and jump around.

Monday, November 18, 2013

First Floor

Last week they did all the layout for all interior and exterior walls on the first floor. It looked like a full scale floor plan, with stacked sill plates as the lines denoting the walls arranged on the floor.
 Next they built the walls, putting vertical pieces (studs) between bottom plate and top plate and voila - it is looking more like a house than a dance floor! Now you can really walk around inside and see what the rooms feel like.(the diagonal boards you see are temporary bracing and will go away when the walls are given the lateral support that plywood provides)

 As the architect, I like to walk around in the new space and see if anything feels different than I envisioned it when I designed and drew it. It doesn't.

The general contractor verified that all the walls, headers and door/window openings are as they should be. He caught a few spots (a wall under the stairs that doesn't need to be there since it is an open riser stair, a header required where floor joists are to be rotated) that needed a small fix.

As for the framer, he is measuring and making sure the loads all align. This is tricky, to me - because he has to do it "backwards" and "blind". The reason I say that is that I design the loads from the top down, and visually ensure they align on my drawings. The framer of course, has to build from the bottom up, and each layer gets hidden (by the plywood sub-floor) covering the structure below that he needs to land on.

For my mother-in-law, this will be a chance to walk around in the spaces and get more of a feel for the house than I think she could from the floor plans and building sections.

Next up: second floor! (what else would come after first floor?!)

Wednesday, November 13, 2013

A Window into the Architect's Process

While the framers are busy building floors next door, I am reviewing the window schedule at my desk. This house has around 28 windows, and I had to review them and revise some of them.

The building code requires windows in habitable space. There are requirements for natural light and natural ventilation. There are requirements for emergency egress. There are requirements that the actual window unit installed meets certain energy standards. These requirements must be balanced with the aesthetics from both inside and outside and with the function and use of the spaces.

Excerpt from SECTION R303
All habitable rooms shall be provided with aggregate glazing area of not less than 8% of the floor area of such rooms. Natural ventilation shall be through windows, doors, louvers, or other approved openings to the outside air. Such openings shall be provided with ready access or shall otherwise be readily controllable by the building occupants. The minimum area to the outdoors shall be 4% of the floor area being ventilated...

There are exceptions (like bathrooms) and special rules for adjoining rooms. It is not a coincidence that the area of light required is double the ventilation area required - think of a "double hung" style window (typical in the Northeast)It offers twice as much light as ventilation. We like light in our homes. Architects like to use a lot of windows. Designs today generally do not have a problem meeting these requirements.

Excerpt from SECTION R301
Basements with habitable space and every sleeping room shall have at least one openable emergency escape and rescue opening... they shall have a sill height of not more than 44" above the floor.... minimum net clear opening of 5.7 square feet... minimum net clear opening height shall be 24"... minimum width shall be 20"... shall be operational from the inside of the room without the use of keys or tools...
The three bedrooms on the second floor of this house each need an egress window. This architectural style typically utilizes double hung windows, but with only one sash - bottom or top- opening, a double hung window has to be excessively large to meet the clear opening area requirements. (this large opening is to accommodate a fire-fighter, in full gear, climbing in to rescue you). Such a large window would look WAY out of proportion, especially on the second floor, so architects have a trick. I specified one casement window, the same size as the double hung windows in the bedroom and with a lite pattern to match. (so it has a horizontal band across the middle, to make it look like two sashes) A better proportioned casement can meet the egress dimension requirements, because the whole window swings open from the side.

Windows are so important in our buildings for views, light, air, and safety. I hope this post gave you a "glimpse" into some of the things an architect has to consider. We'll talk about the energy efficiency of windows in a future post.

The Letter of the Day is "F"

Frost on the Framing this morning! Today was very cold all day - honestly I cannot imagine working outside all day in temps like this- but Scott and John did it. And they Finished the First Floor!

If there was a sound of the day, it would be a loud BOOM. This was the sound that rang out periodically as the guys aligned the edge of each 4' x 8' sheet of 3/4" plywood (read: HEAVY!) against the previous sheet and let it fall into place.

Yesterday they had finished installing the floor joists and girders and steel columns in the crawlspace. We'll look more at how that all fits together in another post. The crawlspace is covered over now, with the only way inside through the opening in the back of the foundation. There will be a floor hatch, but they've decided to frame that later.

Sill plates are next, and marking out the interior wall locations. If the plates around the perimeter look "skinny" to you, it's because the exterior walls of this house are going to be framed with 2x4s instead of the more typical 2x6s. The framers commented on how infrequently they build exterior 2x4 walls. I made this decision while detailing the wall section to energy star standards. (using "CI" or continuous insulation) With the continuous exterior rigid foam insulation these walls will have, we don't need so much cavity insulation between studs, so using less wood makes sense. Continuous insulation performs better for many reasons than cavity insulation alone. With it's air sealing and insulation details, this will be a snug house. Next year, when the cold fall winds blow like today, my in-laws will be warm and toasty inside.

Monday, November 11, 2013

Sill Plate

So far the construction has been all about moving dirt and pouring concrete, but this morning, the excavator back-filled the soil around the foundation, loaded up his machine, and drove off. The lumber yard made it's first delivery of wood to the site and the framers arrived to start building on top of the foundation that has been constructed.

First Scott connected a heavy duty wire into the electrical panel in our basement, and ran electricity next door for their tools. This was decided upon so using noisy, expensive, gas-powered generators could be avoided.

shims ensure a square and level floor
They worked to clean up the top of the concrete foundation wall with a broom. They rolled out foam sill sealer that acts as a barrier between the concrete below and wood above. They drilled and installed the 2x8 sill plate, which is the first piece of wood placed onto the foundation and is pressure treated for that reason. Pressure treated wood can resist moisture better than regular wood, and concrete in the ground can wick moisture, hence the treated sill and the foam it sits on where the two materials meet. The bolts sticking out out of the top of the foundation wall go through the sill plate and nuts secure the foundation and wood together.

Next the rim joist was installed around the perimeter. This is a 2x10 on edge (it is whatever size the floor joists will be). All this work is really precise, with the guys checking the diagonals often to be sure the base of the building is square, using a laser level and shims to adjust when needed to make the top of floor level.

After the rim joist was installed all the way around the perimeter, the first center girder was installed. In this case, it's an LVL -engineered lumber - stands for "laminated veneer lumber" and in the photo it is more a medium brown than the dimensional lumber, which looks almost white. The girder sits in the beam pockets in the concrete walls and is supported in the middle on concrete filled steel columns (that are red) that rest on the thickened footings that were poured with the slab floor. The girder is what holds up the floor joists, and this afternoon before they left for the day, they had installed a few floor joists that rest on that LVL and cantilever out over the foundation wall to create a bay window in the dining area.
cantilevered floor joists

Tuesday, November 5, 2013

The Slab

This afternoon the slab was poured inside the house. Last week, back fill and gravel were placed inside the foundation walls and compacted. The interior footings were located, formed, and reinforced with steel. Speaking of forms, you can see the tall wood blocks sticking up out of the wall. They were placed there before the foundation wall pour to create a space for a structural floor beam to rest. That's called a beam pocket. Perfect example of how things that need to happen in a later stage of construction need to be coordinated earlier, as well as how the different trades need to coordinate.

A thick poly vapor barrier is laid down under the entire slab to prevent moisture from the ground entering the slab. If reinforcing is being used, it would be placed. This slab does not have any steel reinforcing in it. The concrete trucks delivered concrete that had fiber reinforcing in the mix, and this will replace the steel mesh that usually helps strengthen concrete. Because this is only a short crawlspace and the space won't be used for mechanical systems or storage, the slab is what is called a "rat slab". I don't know how it got that unbecoming name, but it just means it's 3" thick instead of 4" and possibly made to less stringent standards than a slab that needs to withstand a lot - like in a garage. Remember this slab is essentially on grade, so no drainage was necessary, either.

I wasn't around to see the masons "float" the slab, but they had some amazing equipment - like a float with a 20' long handle and a gas-powered float. Those tools, and their skill, allow them to finish the slab to be durable and have a smooth surface - floating the fine aggregate to the top without bringing too much water to the top.


 Today was an exciting day at the new house next door. This morning I met June, of Hudson Valley Rubber-Wall; it's always great to see another woman on the construction site! She and her assistant sealed the exterior face of the concrete foundation wall with a rubber coating. Concrete is very absorptive, and when located underground, it can wick up moisture, so we apply a barrier that helps prevent water migration from the ground into the wall (and into the building). In the past, this barrier would be made of asphalt that was sort of painted on thick and messy, but spray-applied rubber is a much greener and more sophisticated approach. (literally green, too!)

After daubing at the clip spots and then spraying the entire surface of the walls, they applied 2" exterior rigid insulation to the outside of the foundation wall. This is also exciting to me because I detailed this house to have a super-insulated "building envelope" (the line between conditioned - or heated - and unconditioned space). It used to be that basements and attics were left "unconditioned" - it is that way in my house. But smart, modern detailing includes the basement, crawlspace, and attic within the building envelope. This allows for the insulation and air barriers to follow the exterior surfaces (rather than a house that, for instance, has insulation in the ceiling of the basement, trying to separate that space from the heated space above, without success). Much smarter for many reasons that we will discuss in the coming months.

2" thick R-10 foam