I am looking to install a set of steps up to our decking. I am yet to accurately calculate the rise. The ground slopes away from the house so I expect it to be 1700 - 1900mm. I imagine, therefore that I will be looking at 10 or 11 step stringers. (Looking to do 1700 steps so will also be installing a centre brace support.) I'm planning on laying a small concrete slab under the stringers/ brace.
My question: Looking at the 10 step stringer kit by wilmaplex (for example), its specs are that it is for a deck height of 1760 and a width (distance from deck) of 2485. How do I measure where to put the slab?
Welcome to the Bunnings Workshop community @VinceB. It's great to have you join us, and many thanks for your question on step installation.
Would you like to lay the smallest possible slab, or are you happy with something slightly oversized?
For the Wilmaplex Treated Pine Ezistep 10 Step Stringer Kit, the height from where it touches the ground to the deck is approx 1760mm and the first place it touches the ground should be approx 2485mm out from the deck. The easiest way to measure out the slab would be to put a mark at 2485mm. You can presume you'll then need to add at least 200mm onto that for the contact surface. One edge of the slab at 2400mm and the far edge at 2770mm would give you some wiggle room.
Please remember the measurements on the product are approximations, and given this is a sloping block, I'd suggest the best method would be to wait until the stringers are on-site and mock them up. You'll then quite easily be able to see where the slab should be placed.
Please let me know if you have any questions.
That is really helpful.
One more question. Given a single slab with plenty of "wiggle" room, (say 1800 x 300), what minimum depth need I take the concrete?
It's great that @MitchellMc has given you excellent advice. I suggest checking with your local council on the decking stair slab thickness requirement. There may be rules and regulations in place on how thick the slab should be and how deep it needs to go. Some of the things that you need to consider when building the slab are the static weight and the weight of the people that will be walking on it. If not built correctly that slab could crack or shift. If you had your deck professionally built, I recommend asking your builder what the general rules are in your area for building a cement base for timber stairs.
If you need further assistance, please let us know.