# Forum Home Renovation Decking  Bluemetal's Low Deck over Concrete - Finished but not Finished!

## bluemetal77

Hi Guys - After reading and posting on this forum and with some great advice and critique .. I've finally managed to complete my Merbau (90x20mm)  hardwood (3-4mm gap) deck over existing concrete. I've been meaning to post pictures but had misplaced the digi-camera at home after taking the pics, just found it last night so still haven't taken some recent pics .. will post those soon.  
At a glance, here is the summary of my deck (Pergola built by a professional, but the middle wood-lined roof done by myself!):
1-   Max room to play with under sliding doors: 80mm (about a brick height and a bit)
2-   About 24m2 of decking on existing concrete slab with a fall
3-   Main deck 4.2m x 4.8m and a side step length of 0.6 x 5.6m (pictures soon) - the extended part is a little pond
4-   Existing concrete coated with bitumen rubber compound (bitkote no 3) for some protection against moisture seeping up.
5-   Treated pine joists (70x35mm) coated with bitumen (all 4 sides and ends) as well and laid flat on side
6-   Joists had holes done by flat-spade bit to allow some room for bolts to sit flush
7-   Plastic horseshoe spacers used underneath each joist where the bolt is anchored
8-   Spacing started at 6mm at the top of the fall to 23mm at the low end of the fall (so the deck straightens a bit)
9-   Ramset Dynabolt (Galvanised) 10mm x 75mm and 100mm length used to bolt down the joists over spacers
10- Joists/first board spaced 25mm away from the wall for termite inspections
11- Tools (all Ozito): Hammer drill (burnt 1 in the process - Bunnies replaced it), Torque drill driver (still going strong), Compound saw (1 stopped working - Bunnies replaced it), Smartbit with 3 bits, Jigsaw (to cut the boards straight - i didn't have a circular saw so managed and gave the edges a sand after)   
Notes :Redface:  
Drilling into concrete was a pain! I used almost 4 drill bits (10mm ones, Bosch brand) to do the 95 odd holes, the drill bit would go flat after 25-30 holes!
- Tried using Ankascrews but the concrete hardiness mpa was too strong and the screw thread would flatten instead of cutting thread- Dynabolting was easy
 - just hammer it in and tighten with a wrench, and because the concrete was hard, not a lot of turns were needed
- Had to vacuum each hole after drilling to get rid off the dust and also at some holes used water to aid the drilling
- Once the bolt was in, i covered the hole on the joist with duct-tape and gave it another coat of bitumen so that it becomes waterproof and water doesn't trickle in from between the joists- Plastic horseshoe spacers were only put underneath bolts as its useless placing it anywhere else where the joist is not bolted
- Spacers were glued together (like to achieve 12mm, 3 x 6mm spacers were glued together) 
- i did not glue them to the joist or floor as the bitumen is a bit sticky and when you tighten it bites into it like glue and it ain't moving!
- 25mm gap was left for termite inspections to be carried out otherwise it voids the warranty if they can't see the barrier. I will put in merbau 70x15 boards vertically in the gap and not screw it which can easily be removed for inspection (pics later)
- I bought the Irwin grip tool and put some L brackets on it to help with straightening bowed boards (there where quite a few), It worked well for avg bowed, but some of them were too hard and i had to get my wife to pull and i push and clamp just to get it to the gap.
- As for the gap, i used the plastic spacers at regular intervals.- Also made a jig for the screw markings that i would place over each joist and tap in to get 2 screw markings - helped get all the screws straight in line.
- Speaking of screws, used T17 50mm x 10G counter sunk were used (got it off eBay by a seller called multifixiings) So that's the summary! I'll post some more pics of its n bits by tonight, and also of the little pond that i've made at the end of the deck.  
Have been weathering the deck for a bit (3 weeks) - have given it water washes about 3-4 times and 1 napisan wash. Will do another one soon and then use deckclean before coating.  
A big thanks to all the forum members, my wife who helped me with some important tasks, and my little man who is less than a year old but wanted to help me all along with his own talent!  :Smilie:   Attachment 87997

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## bluemetal77

Here are some more pics of the side-walk decking and the pond at the end of the deck. I've put a little fountain in it as well, the wiring for which was ofcourse done while the decking was still to be laid. Wifey dear has already put some furniture on it even tho we haven't done the oiling yet .. and we are using it almost every evening .. can't get enuf of it ! Had a bit of rain so the exposed parts are wet ... i quite like the color when wet .. so am thinking of going with the Merbau tint of a oil .. probably IG.

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## r3nov8or

you've done a great job.  
sounds like you needed a rotary hammer drill (with SDS bits), rather than a regular hammer drill. they actually make drilling concrete enjoyable  :Smilie:  
you must like maintenance given you've also built the pond  :Wink:  
i also like the ceiling in the verandah.

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## bluemetal77

> you've done a great job. 
> sounds like you needed a rotary hammer drill (with SDS bits), rather than a regular hammer drill. they actually make drilling concrete enjoyable

  Thanks!
You might be spot on .. the hammer drill is prolly for bricks n stuff .. concrete was a bit too hard for it .. oh well done with it now!

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## grechy12

Wow that looks amazing, well done!! 
Great idea with the use of the ceiling under the pergola - was that some kind of built out frame between the fascias to create the space?  And is that glosswood you have used?

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## bluemetal77

> Wow that looks amazing, well done!! 
> Great idea with the use of the ceiling under the pergola - was that some kind of built out frame between the fascias to create the space?  And is that glosswood you have used?

  Thanks Grechy! 
No, no special frame .. just the standard 2 colorbond rafters/spans of the pergola - i put aluminium L brackets along the length (not individual ones, the whole L length) and screwed them in and put a wooden beam in the center and then just slipped the wood panels on to it .. the beam in the center helps to nail each panel in the middle before putting the next one on .. and keeps the boards from sinking in the middle by weight or expansion/contraction .. 
Also put energy saver lights with canopies so that it doesn't get hot for the poly sheet .. 
Ok but this is a decking thread so i'll shut now!

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## Skeletor

Deck looks great. One question - you're not worried about the little ones falling into the water (or worse)?

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## bluemetal77

> Deck looks great. One question - you're not worried about the little ones falling into the water (or worse)?

  It may look like a lot, but the pond area/walls are only 14cm deep and filled with water upto 10cm .. just enough to run the water pump .. If you fall in it, you'll probably get your feet wet :P .. our little one plays in his inflatable pool which takes in 12cm water.. so if he falls, he'll prolly start playing in it .. not saying we'll let him, or anyone else near it! 
Having said that - any pond/water-filled space/pool no matter how shallow needs human supervision - no railing/balustrade can guarantee safety.

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## bluemetal77

JIG and CLAMP 
Hi Guys, I've been asked to put up a pic of the jig i used to get the screws in line .. apparently the jig i made got thrown away in garbage, the attached photo below is the only one i had from the photos i took, so am pasting that and also a diagram of the jig that i drew before i made the jig. Also in the photo is the Irwin clamp i customised to hold the boards together. 
With the jig, its the same wood as the joist, same width, just long enough to cover a decking board and a bit more so that it can hold 2 "legs" on the side. The area of the jig till the leg is basically the 90mm width of the board in length. The legs are flat so that when i place the jig on the joist from the open end of decking .. the flat legs automatically straighten it. I drilled 2 holes in the jig at where i wanted the actual screws to be on the decking board, and put 2 screws through it and let them protrude just enough.  
So everytime i would go to a new joist, i would put the jig along the joist, hold it firm against the decking board itself and lightly tap it on the top of the screws (just used a fist one little blow), that would give me two little pilot locations where the screw protrusions would hit the deck to drill with the smart bit. As you can see, it hardly went wrong. My deck had about 1200 screws, and the 2 original screws i put in the jig didn't go blunt at all, would last a lot more (they were the same decking screws i was using). 
Also, if you notice, the jig's legs can rotate (just screw in the legs instead of glue), this helps in doing the last or the first decking boards with the same pattern of zig-zag. 
Hope the pictures and illustration helps.

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## magellan

Awesome, thanks Bluemetal i am going to use that set up to do mine - thanks for posting the pics

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