Thread: deck over existing concrete

hi guys first post for me, hope you can help.
i am contemplating putting decking down out my back door on an existing concrete patio that has a slight gradient and am wanting to keep the height of this deck at a minimum ie. 1 to 1.5 bricks. Am i able to lay joists directly on this concrete using brackets to take up the gradient? or is there another method i can use? if i can use the brackets is there a certain type that will work best? Should they be spaced as bearers would be? How to fix them to concrete? so many questions so little knowledge. thanks for reading, thanks even more for any help.

I just did a deck at my son's place using threaded rod a builders washers...have a look a bit further down the page...new deck, no bearers

Just use joists over plastic spacers ... you need room between joists and the concrete for the air to flow and water to drain away ..

I've just built one the same way .. my highest point was 1 brick height .. so i had to lay the joist on its side rather than vertical .. came out all good n solid .. will try to post some pics soon ..

My concrete slab also had a gradient.. so i sort of followed it but gradually increased the spacers under the joist .. started at 6mm spacing and finished at 23mm spacing .. so the deck gradually levels over the gradient concrete .. also, i had painted the joists in bitumen rubber for waterproofing and then dynabolted it directly to the concrete over spacers ..

Hope this helps!

but I would use ankascrews or similar rather than dynabolts. Also search the decking threads, this has been covered countless times.

thanks for the ankabolt tip. they look heaps easier than dynas. taa

couple questions bluemetal. what r these plastic spacers? do i fix through the joist or with a side mounted bracket? and lastly thanks for the tip about bitumen rubber, as this area being flooded under heavy rain is the reason for the deck in th first place. would love to see the pics of yours might answer some of the stupid little questions that i cant answer for myself until i stuff it up! cheers and happy australia day!!!

Originally Posted by stevoh741

but I would use ankascrews or similar rather than dynabolts. Also search the decking threads, this has been covered countless times.

I actually did ankascrews first .. but the mpa of the concrete was so hard that the screws were just not cutting in .. the thread would flatten .. was hardly getting 1 screw done in 20 mins ... i got dynabolts and holy moly ..5 mins max for each screw .. so depends how hard the concrete is .. i recently used the same ankascrew in brick to hold the clothesline and it worked a charm there .. so weigh it up i'd say ..

Originally Posted by late70sbv

couple questions bluemetal. what r these plastic spacers? do i fix through the joist or with a side mounted bracket? and lastly thanks for the tip about bitumen rubber, as this area being flooded under heavy rain is the reason for the deck in th first place. would love to see the pics of yours might answer some of the stupid little questions that i cant answer for myself until i stuff it up! cheers and happy australia day!!!

Happy Aussie Day to all you great forum people!

Plastic spacers are these: 200pcs - 6mmx40mmx75mm SOLID PLASTIC HORSESHOE PACKERS | eBay

I actually purchased it from the same guy in the listing above. I just drilled the dynabolt through the joist and use these spacers underneath .. they jam in rock solid once you tighten it .. i did use glue on them to stick them together but did not glue them to the joist/floor as my joist and concrete were both covered with bitumen and that is kinda sticky itself - enough for it to not move ..

Its not funny but i cant find my camera with which i took the pics .. i'll make a point to search it and put some pics up .. im right now making a little pond near the deck so decking part is all done!