This morning, in glorious sunshine, we were ready to put up our newly created “C” set of rafters to build up the framework of the Front Porch roof. We drilled a series of clearance holes for our fixing screws and then started installing them, the longest one first. This one, C8, went in very nicely and seated good and firmly into place. We proceeded with the next two rafters, the C9 and C10, and it seems to be ok as well so those two were glued and screwed into place too. It was only after this, when we went on to the next rafter, C11 (getting shorter), that we noticed that something was wrong. This rafter was angled somewhat off the vertical line and questions started popping into our minds. We measured the bottom separation (on the C beam) and that seems to be ok at 611mm distance between C8, C9 and C10 but at the top end, they were definitely diverging and we could not understand why this was happening. The spreadsheet had the two measured distances for C8 and C12 and the middle rafters (c9 through to c11) calculated but something was wrong. It was only after we tested the last rafter (C12) that we finally found the “Mistake” .. the position for C12 was 100mm off!! Somehow, reading the measuring tape, we had managed to get an extra 100mm further along the C beam away from its neighbouring rafters!
This completely explains why our rafters weren’t fitting AND also why our smallest one, C13, wasn’t fitting too. So we unscrewed and took back down the last two rafters (C9 and C10) but left behind C8 because that was truly an accurate and measured and it is correct.
We will scrape off the excess brown glue after it had set with a razor blade. These rafters are too short to go anywhere else, including the other side (matching C5 down to C1) or on the Side Porch. The only solution is to reuse them again for the C4 through to C2 rafters by losing about 500mm off the lengths as waste but keeping the Bird’s Mouth ends that are already done. We will have to recreate a new set of rafters for C9 across to C13 and try again. The spreadsheet has now been corrected with the true number (the measurement for the ill-fated C12 was really 566mm instead of 510mm) and it shows how much difference it makes!!
We are only glad that we had the mind to spot this error before the brown glue set and as it gave us the opportunity to make amends! Phew!!