A short - or tall - update on the greenhouse

I've been taking pictures of Rat working on the greenhouse project and thought you'd enjoy a peek at the progress. Also at the end of this post, I put a bit more info on some greenhouse specifics that I found on another useful Coop Extension document, this time from U. Alabama.

Rat first did an assessment of the doors. (We decided not to use the four sash windows we got along with the doors - will save them for a coldframe project.) The four glass doors that will form the south side wall of the greenhouse are in pretty good shape. We just have to figure out blanks to fill in the holes where we'll remove the doorknobs and locks.


The narrower decorative doors were OK in some places...

But not in others...

So Wood Rat did some repairs...

Then it was off to the hardware store for materials to build the foundation...

Total cost for foundation materials (plus a few things like nails): $180.59.
Rat quickly got to work.

He dug holes and filled them with builder's sand (that grey stuff) and bedded in the premade piers (He decided against pouring the concrete since piers are so much more convenient, and good enough for engineering purposes.)

See how nicely Rat put up the batterboards and strings to get the building good and square.

Metal plates make a neat join. The foundation is the only part that has the pressure treated preservative filled wood (there's a proper name for it). The rest of the wood is douglas fir (which grows here natively!).


Voila! --

Then before you can say Jack Sprat, the walls are framed:

Total cost for the wall and roof framing materials: $285.96.

The north wall (facing the pool) will be shingled and it will have the six windows recycled from the house's cupola. The roof on the north side will be shingled with roof shingles, with two roof vents in it. Thus it will match the pool shed on the other side of the pool, and inside I'll have work benches for potting along that wall.

BTW, FYI - here is yon cupola wherof I spake, with the rest of the house under it.

Meanwhile back at the greenhouse work site, I have just asked the question: "What is that damp patch below the electrical outlet there?"

Rat dug out around the outlet. Town Mouse has often opined that a water feature would be really lovely in our south garden. But I don't think this is what she had in mind...

The water comes from the swimming pool. The electricity is for a light in the pool. The pipe has corroded, and we are puzzled as to how to fix this. So we do what we always do when electricity puzzles us. We call on ---

The White Mouse! - aka my dad, and the household's chief electrician. I hope when I'm 94 I'll be helping someone solve a problem, too. Actually we agreed that it's a Big Problem and to just turn off the electricity for now. We'll have to drain down the pool, remove the light, and either replace the corroded pipe etc, or remove the light and seal it all up. We use the light maybe once a year. Still.

So the footings are in, and the walls are framed. What about the roof? What materials? Glass or Solexx? The greenhouse is already a mix of two styles - traditional greenhouse with white paint and glass on two sides (south and east), and more of a potting shed look, cedar shingled walls with windows on the other two sides (north-facing pool side, and west gable wall). So we decided adding Solexx would take it beyond eclectic and into chaotic. We're going to get 3/16" tempered glass cut to order, and do strips of it on the roof about 22" wide. Rat has it all figured out.

So what pitch should the roof be? Rat did some mockups so we could check the aesthetics. Here is a 5 pitch roof:

We looked at it from all angles:



Then he put up a 12 pitch mockup:

Oh dear!
Way too tall! But is 5 pitch steep enough? Today I got a great piece of objective info from a University of Alabama Cooperative Extension page, Hobby Greenhouse Construction:

Roof pitch for a glass greenhouse should be 6-inch rise per foot (27 degrees) to prevent inside condensation from dripping on plants. Plastic-covered greenhouses require a steeper pitch of 7- to 8-1/2-foot rise per foot to prevent drip.

We consulted Rat's Roof Framer's handbook and figured that a six and a half or seven pitch, just a bit higher than we had mocked up, would work fine, and would look good.

Extry Extry! - Just adding this in - this afternoon Rat mocked up a seven pitch roof and we like it! (He also framed the other gable end wall.)


Greenhouse Advice from U. Alabama
I'll just close with a few other nuggets I found useful, from the same Extension page I quoted above. They are about ventilation (we decided we have just enough) and benches (a topic of upcoming interest for sure!).

Ventilation
The purposes of ventilation are to exchange carbon dioxide and oxygen, to remove hot air, and to lower relative humidity. Hobby greenhouses can be vented by natural flow-through ventilation or by forced-air ventilation. Flow-through ventilation relies on side and top vents that pull cool outside air into the greenhouse through the side vent as warm air rises and exits through the top vent. The combined side and top vent area should equal about 20 percent of the roof area [my emphasis]. Vents can be manually controlled, but this requires frequent temperature checks and vent adjustment according to outside conditions. Using an electric motor and thermostat for automatic vent control is much easier. Simple automatic systems open or close the vents based on a setpoint temperature.

Benches:
If you plan carefully, 70 to 80 percent of the floor area can be devoted to growing plants. Make sure that the supports for benches are strong enough to hold the largest number of plants and the largest container size anticipated. Wood, metal pipe, or concrete block can be used as bench supports.

Also make sure the bench surface is strong enough to support plants without sagging but that it is open to allow water drainage and air movement. Spruce or redwood lath and 14-gauge welded wire fabric or expanded metal make a strong, long-lasting, open bench top.

Benches should be 2 to 3 feet wide with access from one side or 4 to 5 feet wide with access from both sides. If using solid-topped benches, set them back from the sidewall of the greenhouse by 6 inches to allow air movement. No setback is needed for open-top benches.

Benches should be 24 to 36 inches high; for individuals in wheelchairs, bench height should be 30 to 36 inches, with little or no surface lip. Place bench supports 6 to 12 inches back from the surface edge to provide knee room.

Here endeth the quotation. And the post.