A 12 x 8 foot backyard storage shed, stick built. The location chosen was near a back corner of the lot.
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The general recommendation for site preparation is to spread about two inches of gravel over the entire area underneath a shed, and to have the shed sit on concrete blocks or pressure treated timbers at least four inches above the ground.
We decided to have four footings, one at each corner. We excavated about 24 x 30 x 12 inch deep holes which we filled with gravel to flush with the ground surface. We set nominal 16 x 8 x 4 inch solid concrete blocks on their sides atop the gravel. Two blocks were stacked at each corner to put the shed 8 inches above grade. For a 12 foot long shed that would leave a 112 inch unsupported span which we later found out resulted in measurable sagging in the middle. We will have to excavate for additional footings in the middle which we have not done yet. With six footings, regular hollow core cinder blocks would probably be adequate. From front to back, the open distance between footings is 80 inches. We do not expect to add more footings on the sides.
The ground was left untreated under the shed. Some grass was there originally and allowed to die off.
We are continuing to evaluate how much if any settling of the footings has occurred.
Materials: Eight 16 x 8 x 4 solid concrete landscaping blocks. One more similar block, 16 x 8 x 2, to compensate for irregular ground level at one corner.) One quarter ton 1/2 inch pea gravel (We purchased a half ton anticipating other projects.)
We used 2x6 pressure treated lumber, with two rim joists at front and rear, and joists at 16 inch centers. Most standard grade commercially prefabricated sheds had 2x4 floor joists at 24 inch centers and single rim joists. The footings were arranged so the ends of both rim joists and of the outermost (cross) joists rest squarely on the footings.. We nailed extra blocks of 2x6 material, a little over a foot long each, in the corners to better distribute weight on the concrete block footings and give some support directly to the second joist on each side..
With the double 2x6 rim joists we did not expect the sagging mentioned in the previous section. Commercially available (8 x 8 foot) sheds often have 80 inches of unsupported span of a single 2x4 joist between footings.
Both end nailing and joist retainers were used for those joists (six of them) not over the footings.
Materials: Five 12' 2x6 PT (one cut into short sections), ten 8' 2x6 PT, twelve metal joist retainers.
The floor was first planned to be 1/2 inch pressure treated plywood. We made the mistake(?) of installing the floor panels parallel with the joists, and some sagging between joists was noticed. The sagging might have been avoided with thicker plywood but at any rate we will end up putting another layer of plywood, cut to fit on the exposed floor inside the walls.
We kept the floor as dry as we could using a plastic sheet weighted down with bricks and lumber. When the walls were put up, the edges of the sheet were turned up to collect most rainwater which was drained off before work resumed.
Materials: Three 4x8 1/2" PT, three 4x8 1/4"
We used 2x4 framing. Side walls had (seven) studs on 16 inch centers, going all the way from front to back. Front and back walls had studs on 16 inch centers near the middle and approximate 16 inch centers near each end. Front and back walls have studs at each end butting up to the side sections putting two studs at each corner of the shed. Most consumer grade prefabricated sheds had studs on 24 inch centers with just one stud at each corner. Each wall's framing including the 12 foot walls was done in one section lying flat and then raised into position. After all four walls were up, a second top plate was added, interlocked at the corners.
The door opening had double studs at the sides and double 2x4 headers. The door opening was sized for a 40 inch wide door. No casing was planned so the rough opening would be the finished opening. This resulted in stud centers being not exactly 16 inches, although no stud spacings exceeded 24 inches. For symmetry we matched the irregular stud spacing at all four corners.
We chose not to install any windows. We figured that all the windows would do was lead to bleaching of the shed contents from sun exposure so we decided to forego the extra cost and framing effort. Also since we planned to ultimately have two sheds, the second shed would have windows if we changed our mind on that subject.
The wall height was chosen so that the 4x8 siding panels would not need end trimming. One plate at the top and part of the joist at the bottom would be covered.
Diagonal bracing was used during framing but not in the finshed shed. Squareness of the walls depends on the siding and its fastening to the studs.
Somehow the tops of the walls did not meet at quite 90 degrees. We had to tie a rope between two corners and twist it to pull the walls to make a perfect rectangle at "ceiling" level. Later irregularities in installing the roof sheathing suggested that the tops of the walls drifted back out of squareness as construction continued.
Materials: 34 8' 2x4's, six 12' 2x4's, one 8' 2x6 to construct doorway header.
We chose for siding a textured plywood panel with widely spaced vertical grooves on one side. As it turned out, the grooves made the painting more time consuming. Three full 4x8 panels cover the back. On each side two full 4x8 panels are upright side by side and two triangular pieces are placed directly above them respectively to cover the gable. The panels had shiplap sides, as the vertical edges as the panels were mounted.
The siding stops short of the bottom edge of the flooring (rim) joists. This is probably an error since it allows water to wick up under the siding at the bottom. Instead the walls should probably have not been made quite as high and the siding should have extended below the floor joists to act as its own drip edge.
Siding was fastened mainly with galvanized nails, with drywall screws used in a few places.
No drywall or other wall covering is planned for the interior.
Materials: Eleven 4x8 panels, one cut into triangles and other small pieces to cover roof gables.
These were 2x4's on 16 inch spacing. (The standard grade commercially produced shed uses 24 inch spacing.) We started with the rafter pairs at the ends (gables), installing the ridge 2x4 immediately. To expedite assembly up in the air, pairs of rafters were joined near the top ends with a very short collar tie that would contact the ridge 2x4. No other collar ties were used although we expected to mount a few 2x4's horizontally at plate level to keep the walls from bowing out and also to serve as framing for overhead shelves. Some of the rafters were toenailed to the plate, others were nailed to a short piece of 2x4 which was in turn nailed to the plate. We used one inch high birdmouths (notches) in the rafters to join with the wall plates.
Due to a miscalculation that we forgot we made, the rafters other than the pairs at the extreme ends were all cut about a quarter of an inch shorter. This resulted in some irregularities when the roof sheathing and some of the trim were installed.
Only three studs framed each gable, one in the middle (peak) and the others 16 inches on each side. This left about a 32 inch unsupported horizontal span to each eave but the vertical span between plate and rafter was less than 24 inches so the sheathing would still be adequately supported. Each of these studs was notched at the top to extend up outside of the collar tie or inside of the rafter, respectively, rather than being just butted up from below.
At least one three inch drywall screw was driven directly to hold each rafter tip to the ridge 2x4, that is, two screws per rafter pair to begin with. For some rafters, a second screw was driven at an angle, simulating toenailing.
Materials: One 12' 2x10 for ridge, 20 8' 2x4's, two 12' 1x4's for eaves,
This was ordinary half inch plywood. We used screws (drywall screws) rather than nails for installation. We chose to create a ridge vent.
For the 12 foot long building three panels in the front and three panels in the back should have been a natural fit. We installed the left and right panels first, using drywall screws to fasten them to the rafters. Somehow we needed to trim about a quarter inch from the center panel to make it fit. In order to provide access via ladder to the center of the roof as long as possible, one center panel (in front) was installed in two pieces, an upper half and a lower half.
Construction slowed considerably at this time. We had a blue plastic tarpaulin covering the roof for two winter seasons and the summer in between. This tarp was held in place by ropes to a fence behind the shed and also by weights hung from the grommets in the tarp. There was a marked tendency of the tarp to billow in the wind and we added two hold down cords running across the top of the shed from back to front, tied to fixed objects on the ground.
In the months prior to shingling, portions of the roof sheathing were painted with primer to better shed rainwater during times when the tarpaulin was removed for work. This priming was somewhat random depending on what portions were exposed.
Materials: Six 4x8 nominal 1/2" plywood panels.
We put aluminum drip edge both on the gables and on the eaves. At the gable, the 1x4 trim piece was outermost, then came the edge of side sheathing which was about 5/8" thick, then came the roof sheathing. This made the overall roof a few inches more than twelve feet side to side. The gable drip edge was nailed to the 1x4 trim on top using thin galvanized nails. (We did not put an extra 1x1 wood trim strip on the outside of each gable to hold the drip edge.)
Fifteen pound roofing felt was used over the roof sheathing. After installing this we discovered we had some 30# roofing felt left over from an earlier job, although we did not measure that after the fact to determine whether there was enough.
We had to use staples to hold the roofing felt down given windy conditions. At first we cut squares of duct tape and applied these to the felt and stapled through them. Expansion and contraction of the structure and the felt caused undue puckering so we had to remove the staples and tape prior to actually laying the shingles. For better or worse we put a dab of drip edge adhesive on each nail hole in the drip edge, but not on each hole in the felt made by staples.
Ladder access from the inside of the shed to the center of the roof was maintained all the way to this point. In back, where the roof sheathing was complete, two simple side to side runs of roofing felt were applied. In front, the two roof sheathing panels already installed on the left and right were partly covered by felt applied from bottom to top, as much as the width of the felt would cover. The lower half of the front center panel was installed and a side to side layer of felt applied at the eave. After the back was completely shingled, the last piece of roof sheathing was installed. Finally the top center of the roof was covered with a trapezoidal piece of roof felt, with considerable overlapping of the felt already installed.
We put on starter rows of of shingles (minus the tabs) going up each gable and along each eave. For the main shingling we used an approximate one foot stagger per row, cutting the 37 inch shingles into just 13 and 24 inch pieces where needed. Estimating the materials was a close call. Four 37 inch shingles exactly covered one row. Had the shingles chosen been 36 inches long, the project may well have required another (approx. 33 sq. foot) bundle. Main shingles are approximately flush with the starter shingles but both extend about a quarter of an inch past the drip edges on gables and eaves.
We chose a 4-3/4 inch exposure for the shingles, which would leave slightly less than 4-3/4 inches for the topmost course. (The normal exposure was 5 inches.) We were not absolutely sure what the cap shingles would look like when finally installed so we wanted to make sure that the topmost course would not be just a little more than 5 inches.
We put three roofing nails in the 13 inch shingle sections, four nails in the 24 inch sections, and five nails in the full 37 inch sections.
To prevent cumulative errors, we measured each shingle's position all the way from the bottom shingle's edge rather than 4-3/4 inches from the previous shingle's edge.
To keep the ladder from damaging the shingle edges at the eaves, we fastened a long piece of scrap lumber to the soffit using blocks of wood as horizontal cripples to hold the piece an inch or so out from the edge of the shingles. This rail also had ropes tied to it and had to withstand outward force while work was done from the ladder, so many three inch screws were used to fasten it to the shed eave. We will need a lot of wood filler to hide all of the screw holes once we remove the rail.
The ridge vent baffle was a manufactured rigid assembly made up of multiple layers of plastic material resembling corrugated cardboard to provide the air passages. After it is mounted, cap shingles are fastened on top of it.
Currently the building is open at the eave soffits. We should install screening to keep animals out.
Materials actually used: Four bundles of regular shingles, one bundle of cap shingles, two 4' ridge vent pieces. Unfortunately we overbought shingles, getting six bundles in anticipation of building a second shed. The roofing nails were given to us and we don't recall the quantity. From the experience so far we will probably order a prefabricated shed or omit that part of the project.
Corner and Other Trim:
Where the gable extended past the front or back to provide the eave overhang, a more or less triangular side piece a little under one square foot in area was needed and cut out of leftover siding plywood. Four such pieces were needed, one at each corner, and all four differed in exact shape. Cardboard templates were made for each of the pieces prior to cutting. These could not be part of the main side or gable panels since the body of the shed used up the entire four foot width of those pieces.
Each vertical corner was trimmed with a 1x3 to one side and a 1x4 to the other side. This was needed to cover up the irregular "seam" where the shiplap siding panels met imperfectly at the 90 degree angle.
Not installed yet (Dec. 2007) are horizontal trim pieces at wall plate level and perhaps at foundation level. Special treatment such as beveling will be needed to prevent snow or water from collecting and then seeping behind the trim piece.
Materials: Four 8' 1x3's for corners, seven 8' 1x4's for corners and doorway, two 10' 1x4's for horizontal side trim at plate level, four 8' 1x4's for gable trim.
The simplest door would have been a piece of plywood with stiffening strips of 1x3 or 1x2 on the back. We found some shiplap pine boards which we assembled upright side by side using 1x3 cross strips to make an attractive double door. For the time being we used externally mounted hinges, which does compromise security since they could be unscrewed by a thief. One possibility for improving security would be pins in the door that engaged the side jambs when the door was closed. Hardware currently consists of two barrel bolts at top and bottom of one door leaf, two cupboard door handles, and a surface mount deadbolt lock on the other door leaf.
It was almost two years from the start of construction before any finish was put on the shed. For part of this time makeshift plastic sheeting was draped on the exterior to protect the wood. Still, some mildew occurred. In 2007, stain and mildew killer was applied to some areas and most of the siding was primed. We will probably need to do more stain killing along the bottom edge and around the eaves before continuing with primer and paint.
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All parts (c) copyright 2007-8, Allan W. Jayne, Jr. unless otherwise noted or other origin stated.
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