Two young friends have lofts in their rooms and they were in need of a permanent way to access them. After visiting to take some photos and measurements, we decided on seventy-five degree ladders with treads about six inches deep and eighteen inches wide. We also planned to use 1-1/4 inch thick poplar, to match the existing woodwork leading to the entrances of their rooms. In keeping with the existing woodwork, we chose a Bona Traffic HD anti-skid floor finish, a waterborne two-part finish that would let the beauty of the poplar show through and be very durable.
While a seemingly straightforward project, a few factors made these ladders a bit challenging. Vertical dimensions to the lofts were 107-1/2″ and 108″ respectively, so the stringer boards were over nine feet long. For strength, the eleven 1-1/4″ thick treads per ladder were designed to be let into 1/4″ deep dadoes on each stringer, and secured with four 2-7/8″ HeadLOK timber fasteners each. Machining these dadoes, evenly spaced and at 15 degrees from the edges of the stringers, called for a custom router jig which worked well, until the stringers were compared and a small amount of cumulative error was discovered. This resulted in some adjustment cuts, some custom filler strips and a lesson (re)learned about the stackup of tolerances.
In hindsight, one stringer should have been machined with the router jig as described above, then the dado locations should have been transferred to the matching stringer. The router jig should then have been positioned according to the transferred locations. This method would have resulted in the dadoes matching from stringer to stringer … the first time!
The photos below will illustrate the steps in this project, including the correction of cumulative error due to the stackup of tolerances using the router jig!
Custom loft ladders designed in SketchUp.
Otis’s room and loft.
Otis’s room and loft sketch showing position of planned ladder.
Nevis’s room and loft.
Nevis’s room and loft sketch showing position of planned ladder.
Lumber delivery from LL Johnson in Charlotte, Michigan.
6/4 of Select and Better kiln-dried poplar, sorted to net nine pieces 7″ to 10″ wide and 11′ to 12′ long. Ripped one edge and surfaced two sides to 1-1/4″ thickness.
I had to combine my 4′ and 8′ track saw tracks to rip a parallel edge on the longest boards.
The best four boards were selected for the stringers, cross cut to about 10′ long and ripped to the final 6″ width.
Four clear poplar stringer blanks, ready for the next operations.
Twenty-two tread blanks cross-cut to final length, ready for the next operations.
The stringer dado router jig was designed and ready to build.
More of the stringer dado jig components being prepared.
The bottom band on the reversible jig was designed to register on the bottom of each stringer, and then in the resulting dado for each successive machining operation.
The stringer router jig was built to include 0.020″ of clearance for the treads.
A fifteen degree cut on the bottom of each stringer provided the first registration surface that would result in a 75 degree ladder geometry.
Yup, that’s fifteen degrees, alright! Kidding aside, once the miter saw was set at this angle, all required cuts in both stringers, test and setup pieces were cut before the saw setup was changed.
Router jig registered to the bottom of the stringer on the 15 degree cut (not shown in this photo), ready to machine the first dado. The removable strips around the opening were used to machine the first pass of the dado, then removed to machine the final depth of the dado. (This two-pass technique was later deemed unnecessary for a 1/4″ deep dado in poplar.)
The router jig was registered on the *bottom* of each previously machined dado, but this still resulted in a tolerance stackup that varied between all four stringers. Drat!
At this stage, the four stringers were left long at the top ends, so the tricky operation of translating the target vertical dimension to the length of the angled stringer.
With a carefully clamped board simulating the floor surface and distance out from the vertical dimension, the top 15 degree angle cut could be accurately determined.
A 15 degree bevel jig and drafting square completed the setup to determine the final cut at the top of each stringer.
The target vertical dimension for one ladders was 108″ …
The two stringers for the 108″ ladder were matched up and cut at the same time, to assure that both stringers would be identical in length and configuration.
… and the target vertical dimension for the other ladder was 107-1/2″.
Forty-four 2-7/8″ HeadLOK timber screws for *one* of the loft ladders!
Two part Bona Traffic HD Anti-Slip waterborne finish with hardener.
Using my angle gauge, I tilted the tablesaw blade to 15 degrees to rip the front and back edges of all twenty-two treads.
Ripping 15 degree angles on the treads to match the angle and depth of the stringers.
Treads in process. Several extra tread blanks were prepared after some slight twist was observed in some of the original blanks. Since the tread thickness had to be maintained at 1-1/4″, any even slight twist could not be machined away.
Setup to hand-cut notches for the upper wall mounting plate to nest in.
A very fine bladed Japanese Dozuki (mortise and tenon saw) pull saw was used to make the matched shoulder cuts for these angled notches.
The pull saw was also used to cut away the rest of the notches, with stock left for truing up with chisels and a shoulder plane.
Finished notches ready to accept a wall mounting plate.
For both dry fit and final assembly, an extra piece of the 1-1/4″ poplar was screwed to the bottom of the stringers to simulate the plane of the floor on which the ladder would eventually sit.
After back-drilling undersized holes in the stringer dadoes with a jig, these holes were used in dry fit to match drill pilot holes into the treads for the timber fasteners.
With one ladder dry fit assembled in the background, the second ladder is being dry fit assembled in the foreground.
A project milestone, both ladders shown in their initial dry fit assembled states.
Individual filler strips machined and matched to specific locations on each stringer.
Sanding treads flush to the faces of the stringers, still in dry fit assembly.
Matched treads marked with stringer locations before disassembly.
Getting ready to glue in filler strips after dadoes on one of each set of stringers were adjusted.
Using shims to clamp in the filler strips while the PVA glue cures.
Treads and wall mounting plates ready for sanding and easing of sharp corners.
Filler strips glued in the tops of the dadoes that required adjustment.
Final sanding of stringers in preparation for finishing.
Final sanding of treads in preparation for finishing. Block plane was used to ease sharp corners before a quick hand sand to smooth them.
All ladder components set up for a four step finishing process.
Stringers ready to receive the waterborne two-part floor finish.
Designed for flooring and other large areas, calculations were needed to determine the proper amounts of finish and hardener to mix together in four partial batches.
Four sets of mixing containers and small roller trays after all four steps of the finishing process were completed.
Final coat of finish on the top surfaces of the treads, still wet so shinier than the final satin sheen.
Stringers with the final coat of finish. Fortunately, the anti-skid formulation dried very clear and only left a slight texture but did not feel like “sand” had been added.
Final assembly of the finished loft ladders, ready for delivery and installation.
Four-and-a-half inch timber screws secured the wall mounting plate to the internal rim joist of the lofts.
Nevis’s ladder in place.
Otis’s ladder in place.
Two notes: The cumulative error mentioned above, and the resulting cosmetic fix had no impact at all on the structural integrity of these ladders. Also, handrails will be designed, fabricated and installed before my young friends are officially released to use their new loft ladders!
