Habitat Tutorial – Preparation for Build

Prepartion for build

Layout on the Saturday before the first day of volunteer build.

Caution, take with a grain of salt.  This is from the experience of one volunteer, certainly not an expert and I will make errors.  Keep in mind also that other Habitat leaders may do things entirely different.    If you are looking for slide shows for the 2008 build, start with Dinner on the Slab.

Preparation for build could go all the way back to when Cobb Habitat began site selection through when the concrete or foundations are poured, street and utility construction and other site preparation.   I’m not going that far!  I have also left off details of squaring the slab which involves a careful analysis of the slab dimensions vs the house dimensions and then snapping lines that are perfectly perpendicular in all directions, matching the slab to the plans as best as possible. If the slab is perfectly rectangular and sized correctly, this is a no-brainer. 

Often the slab is not poured perfectly and there are edges that are bowed, edges that dip or turn out, and corners that are not square.  In addition, the middle of the slab can be bowed up (the usual case) or bowed down with resulting puddles after a rain to deal with.    All of these things must be dealt with by adjustments to the layout to accomodate the anomalies – the concrete is poured and hard, the plumbing is where it is, and the volunteers will show up next week, and nothing is going to be ripped up and repoured.  

This tutorial is, instead, a brief summary of the steps that the Site Project Manager (SPM) goes through with a few other volunteers to get the site ready for the volunteers first day of build.  I am also omitting the extra work necessary to build a floor deck in the situation of a house with a crawl space.  This year we are building on a slab withouth a crawl space, so that is all you get.

The previous Saturday several members of our group (The SPM, crew leaders and other invitees) met at the site and measured, “squared”, and “laid out: the site, meaning they checked the foundation and defined the outline of the home and all the interior walls.  This involves laying out every window, door and wall section and outlining them with chalk lines.  Corrections are made with different colored chalk and the final layout receives a clear waterproof spray in case of rain.

There were several problems to be overcome caused by the plumbers miscalculations that put the bathroom 2 feet into the living room and the utility plumbing outside the designated walls in several areas.   Our future homeowner, Nicole was on site and agreed to a bigger closet and a smaller living room and all the adjustments were made to her satisfaction. 

Unfortunately it rained in the middle of the layout, washing much of the markings away.  Since the team ran out of chalk colors (red blue and green) the final outline was done mostly in pencil.   That works too, if you have enough pencils as they wear quickly on concrete.

2×4 pressure treated boards are cut for each wall section to exactly fit the walls (ignoring door openings) and matching “white wood” (untreated) 2×4 boards are made for each one and tacked together in pairs.  The pressure treated boards go on the concrete and the white boards will go on the top of the walls.   Each board is numbered at each end and matching numbers are placed on the concrete between the drawn lines.   There are drawings below to illustrate all this.

The location of all wall studs are outlined on the edges of the two boards and “X” marks placed in the outlines.  The location of Jack studs (shorter studs inside of door and window frames) are marked with “J”. Doors, Windows and T’s and Ladder headers are also marked.   T’s are located at points where walls intersect.  Door types (left hand, right hand, width) and Window sizes are marked on the wall plates. 

The two boards representing a wall (or section of a longer wall) are then placed back into the outline and everything checked again against the print.  Each board has all the markings necessary for a group of volunteers to build that wall in a matter of a couple of minutes without any concern for where that wall will end up.  If they follow the markings the wall will have studs, the proper size door and/or window and all connecting T’s for any intersecting walls.  Any allowances for plumbing (such as slots or notches for pipes) will also be marked. 

In addition, the team builds all the “T’s, door frames, window frames and corners and stack them in a pile.

Marked top and bottom Plates

Here is a fictitious example of a set of plates that have been tacked together and marked.   Normally there is also a wall number on each end.  I’ve omitted that.   The pressure treated board goes next to the concrete on top of a foam strip (“Sill Seal”) that helps seal out moisture and air.   Door openings are cut away later.  X is marked for studs, J for Jacks, T’s are marked (see markings near right end above) and have an arrow on the plate to show which way it is to be oriented.  The size of the door or window is marked on the plates as well.

Corners and T's

These are a few of the components usually prepared before the volunteers show up.  They are build by volunteers during the layout day if they have time, and often finished by the “Gray Ghosts” if they don’t.  Sometimes a team of volunteers build them on the first day of build.  We like to have them ready beforehand if possible to speed things up.

Corners and T’s are built exactly the same except for the orientation of the boards between them.  Corners have the boards wide side to wide side between two studs.  T’s have them positioned narrow side to wide side as shown in the middle illustration.  Plumbing T’s need to be wider so the boards are turned lengthwise (7” long) and doubled up to give them more spacing.   The purpose of the T’s is to give intersecting walls a place to be nailed to. Plumbing T’s need extra space for vents and piping.

The T’s are inserted in a wall and then an intersecting wall fits against the wide part of the spacers and nailed from the back side.   Corner posts and T’s that are in outside walls are insulated.  There is an illustartion near the bottom of an assembled wall with a T.

Door Headers

These are two types of door headers, interior and exterior.  The widths of the interior doors vary greatly.   The headers for 3′ exterior doors are 1/2 inch longer than for 3′ interior doors.    The jacks are often left out of the sets made beforehand.   The doors are set in place in the walls, the walls nailed to the concrete and the opening cut with a Skill saw (carefully set to not ruin the blade) or a “saws-all”.   Leaving the jacks out allow a Skill saw to make the cut using the 1.5 inch guide on the saw.  If the jacks are in place, the saws-all does a good job of making the cut.   Ladder doors get their name from the series of “cripples” that form a ladder like shape.  Exterior doors are always 2 each 2×10 boards with a 1/2 inch plywood spacer between them.  The cripples are often inserted after the walls go up so that they can be matched to the nearest stud placement and to fit drywall or exterior sheathing.   Also, you may notice from the “live” pictures that come in the next tutorial, all the darkened wood in the ladder illustration is sometimes left out in the initial assembly and the top bar omitted entirely so the cripples extend to the top plate of the house frame. 

typical window header

This is a typical window header, often prepared ahead of time whenever possible.  The cripples are usually left off, measured and added after the walls are up and located such that they fall on 16″ centers to match the drywall or exterior sheathing after the wall goes in.  There are usually 3 or 4 sizes of windows in a typical Habitat house.  There is usually a “picture window” size, a shorter kitchen window for over the sink, and then the bedroom and side windows.  sometimes there may be another size for some special purpose, perhaps for a bathroom or next to a deck.

 assembled wall

Here is an assembled “fictitious wall” showing a match up of the plates and the assembled wall section.  Wall sections are butted together for longer walls and the top plates joined by an overlaping cap plate.  The end of an intersecting wall buts up to the near side of a T (in this case the side showing) and the nails are hammered in from the open back side.  Cap plates run from the intersecting wall and cross over to the continuing wall so that they are locked together.  Volunteers can assemble this wall in 2 or 3 minutes or someone that has never held a hammer may delay it for 4 or 5 minutes.  We wait for him/her and give much encouragement and help.  The idea is to have fun.  We are not on a real schedule.

When the volunteers show up, they are instructed to grab the tacked-together plates, separate them and start inserting studs, T’s, window and door units.  It takes all of 2 minutes for the whole slab to be covered with walls under construction.  Volunteers help each other with the more experienced crew leaders make final judgements.  The SPM usually resolves major problems quickly – such as a wall that intersects a door or a window where a door belongs, or a room with no door.  It happens.  The worst case is for windows and doors that arrive that are the wrong size for the frames that were built to the plan.  Tear out and redo is often the solution.

Completed walls are stacked outside on the dirt until they are all finished.  Then the walls for the exterior start to go up.  The first wall stops everything as everybody gathers for the photo-op.   Nicole was photographed driving in the final nail and helping position the wall.    Then the other walls were carried onto the site in an order designed to get them all into place without having to shove any over the top of a wall.   One was anyway.

Our volunteers started active work about 8:30 AM after prayers and safety instructions.  By 11:30 all the walls were up and lunch was served (hamburgers and hotdogs grilled on-site). 

By 3 PM all the walls had been sheaths and the frame squared and prepared for the A frames and roof, including the porch beams.

I’ll show pictures of all the various parts going into place in my next article – first day of build.

Next:  Build Day 1 – Walls go UP!

The next article will have pictures and slide show for the first day of build – the day the walls go up.  Watch for it here.

Oldtimer 

 

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