Low-level decking construction

[Amin88]

Hi All,

I am inspired by the other decking projects posted in this group and also the technical support prvided the expert group. I am planning to my deck project and would like to ask the suggestions as my situation is a bit different from all previously posted decking projects.

my outdoor entertainment area is currently concrete floor sloped with a drop of 180 mm from house level. Attached is the rough cross-section drawing. I prefer to go for the deck finished level same as house level, however, this will allow a floor to ceiling height of 1950 mm at the outermost rafter level which is too low. 

Thinking of dropping the level by 100 mm to allow 2100 floor to ceiling height at the middle rafter level ( I will still only have 2050 mm for the outermost rafter level). But, then the clearance for substructure will only by 60 mm (80 mm - 20 mm decking material) at the house entry level. I am seeking a suitable substructure plan for my decking project.

Cheers,

Amin

[MitchellMc]

Hi @Amin88,

That's a sensible way of attaching the ledger if there is any chance you might want to remove it. I'd suggest glueing threaded rod into the concrete with Ramset 750ml ChemSet 101 Masonry Anchoring Adhesive Cartridge. You can then use a nut to attach the timber. 

Mitchell

[Amin88]

Hi @MitchellMc thanks for your prompt response. Do you have an schematic / image to show your described way of attaching to concrete? Is it a standard practice or I am better off choosing the dynabolt?

[MitchellMc]

@Amin88,

I apologise. I misread your post and presumed you wanted to fix a ledger into the side of a concrete slab as per your image.

If you want to fix your joist down to the concrete slab, you could use Ankascrews as normal bolts won't screw into concrete. These Ankascrews could be removed at a later date if needed.

I hope that clarifies.

Mitchell

[Amin88]

Thanks @MitchellMc. sorry to bother you. what diameter screw would you recommend and what spacing in the joist

[MitchellMc]

@Amin88,

If you are counter-sinking them, something like a Ramset 10 x 100mm Galvanised AnkaScrew Masonry Anchor would be suitable. You could space the screws 500-700mm apart.

Keep the questions coming, I'm here to help.

Mitchell

[Amin88]

Thanks for the continuing support @MitchellMc . Before driving the Ankascrew, what diameter drill bit should I use for predrilling the hole in concrete? Should 10 mm drill bit suffice or should I choose slightly less Dia hole (I.e., 9-9.5 mm)?

[MitchellMc]

@Amin88,

The hole drilled should be the same size as the Ankascrew. For a 10mm Ankascrew, you'd use a 10mm drill bit. The thread will then cut and bite into the concrete. If you use a drill bit smaller than the screw shank, you'll run the risk of cracking the concrete.

Mitchell

[th-DIYER]

Hey @MitchellMc  this is connected to another post I put up earlier and then saw this cool project that @Amin88 is working on. 
My small 1000x800 step/platform at the bottom of a staircase is also being built on a concrete slab that is sloped. Instead of using angle brackets and trying to get the frame level with shims could I use these adjustable pedestal feet? My only concern with it being a little platform I would want to secure the feet to the concrete when I have the right height. Is this possible?

Thanks in advance. 

[pete_brig]

Hi @Amin88 / @MitchellMc 

I'm not a builder but Heres my thoughts, for what they're worth.

If the deck area aligns with an outdoor area of the house, consider keeping the deck height level with the house to create a large flat area--lower clearance at the outer edge of th roof--1950mm-- is still adequate for th majority of ppl and may look low but a larger flat area is more functional.

Otherwise the step down is a good option, and can be used as a feature even if the deck is beside an outdoor area of th house (think of sunken lounges inside a house). Your suggested stepdown of 100mm is good to avoid it becoming a trip hazard. (I think 125-150mm is typical step height in stairs?)

Seeing as you're building over th existing floor, you could consider removing some of it (excavating) beside the house to give more room for your decking timbers. More work. Otherwise keep th spacing between the joists small as @MitchellMc  suggested to avoid bounce in th floor.

Cheers, Peter

[StevieB]

Great to hear that you've been inspired by @Amin88's project, @th-DIYER.

@MitchellMc will be more than happy to help with your question when he's back on the site tomorrow. Thanks for your patience in the meantime.

Stevie