Workshop
Start a discussion

The Workshop community can help with your home improvement projects.

Merbau decking over concrete slab

Highlighted
Junior Contributor

Merbau decking over concrete slab

IMG_20191207_141119.jpg

 

Hi Everyone 

 

I have been going through these discussion boards for a while and finally mustered to courage to post a question here :smile:

 

This would be my first deck. Have done some landscaping for myself in the past including a raised garden bed, however nothing major. As far as tools, I've a drill kit including hammer drill, a cordked circular saw and a random orbital sander. 

.

My proposed deck would be 350 x 370 with height from the slab between 17 - 18 cm so it stays flush with the brick and same level as my internal floor. 

 

I've been advised that i could use H3 structural timber (140 x 45) as joists and lay decking boards on top that. 

 

My questions, 

 

1. How do I attach joists to the concrete? Use galvanized angle brackets like this?

 

2. How can I adjust the height so the finished decking board stays flush? If i used 140 board + .5 bracket + 19 mm board = it would be around 165 cm height. Which is around 1.5 cm lower than bricks. Can I use plastic wedges / window packers to compensate for around 1.5 to 2 cm? 

 

3. This deck would be under alfresco cover and under eaves. In terms for water drainage, what would be helpful. Would the packers / wedges mentioned in Q. 2 help with the same?   

 

IMG_20190916_143835.jpgAlfrescoAlfrescoRough plan showing pillarRough plan showing pillar

On the last image, pillar is on the corner of the alfresco slab and the decking to the south of it would be on top of soil (this would 370 x 45 cm). Not much height difference from alfresco slab. What do I need to provide here under joist for support? Not enough height for a stirrup. 

 

Thank you very much for reading through. 

Highlighted
Community Manager
Community Manager

Re: Merbau Decking over concrete slab

Heya @Neo19,

 

Sounds like a fantastic project. We are pleased you have joined in the discussion. Let me tag @Brad who might like to kick off the replies to assist you with your decking questions. 

 

Please let me know if you ever need a hand getting the most from the site. We are looking forward to seeing how your deck progresses, and are sure you'll get loads of helpful advice and inspiration from the community for this job as well as many others to come in the future. 

 

Cheers,

 

Jason

 

See something interesting? Give it the thumbs up!
Reply
Loading...
Highlighted
Trusted Contributor

Re: Merbau Decking over concrete slab

Thanks @Jason 
I think your on the right track with using brackets, they are stronger than the ones supplied with most kits and unless your budget is tight it won't matter much for that size deck. I would dynabolt the brackets to the concrete with your brackets on the inside so they are hidden once the decking goes on and I would start with getting the flush fit with the door once the decking is on and then level it from there. Temporary packers as the is only around 20mm and as much as I like using feet there is not much room for them. Plastic or DIY timber wedges will work, door stops from the local cheap shop works for me just have to keep the my dog away from them.

Drainage would be helped by having the frame off the ground and it also helps stop junk building up against the frame. Once you have the frame fixed with those brackets there is no need to leave the wedges in.

My question is why do you want the deck to extend past the house? I would have it flush with the house. I would stop the brackets before the edge of the concrete and with your specs 500mm overhang shouldn't be a problem and you can test by standing on the frame and if it flexes then you need to fix it. Biggest risk of that is around the pillar and you may have to dynabolt to the pillar to get it stable.

One least tip before I have breakfast is to seal the cut ends of your frame as that is where the weak spot is with H3 treatments.

Reply
Loading...
Highlighted
Junior Contributor

Re: Merbau Decking over concrete slab

Thank you very much for your very detailed response and advice. I really appreciate your inputs.


When you say brackets on the inside does it mean the horizontal bottom which is dynabolted to concrete slab stays underneath the h3 timber like my rudimental drawing???

 

IMG_20190921_160755.jpg


Am I ok to have 3 brackets per timber (3.5 meter length) or do I need more?


“I would start with getting the flush fit with the door once the decking is on and then level it from there”


Forgive me if this question sounds very stupid, but how can I level further once the frame is bolted to concrete before I lay decking? Wouldn’t the packers go underneath timber frame before I attach them to the bracket?


Am I OK to have only one screw per bracket although there are two holes? That way I could raise the timber from floor by 2-3 centimetres.


I wanted to extend the deck past the house to maximize deck space leaving just enough room for a single column stepping stone path. Also there is a water / gas point on the brick pillar and if I wanted to add a gas barbeque I could keep it in that corner. There would be only 35 x 45 cm over hang next to the pillar. It’s less likely that anyone would every stand here in terms of load over deck.


Also as you can see on the first image, alfresco sliding door is more or less flush on the left hand side while the sliding door on right hand side is recessed and one layer of brick is exposed. Do I leave this brick exposed or do I cover it with decking board?


Thanks for reading through.

Reply
Loading...
Highlighted
Trusted Contributor

Re: Merbau Decking over concrete slab

While it's not the best photo for showing how to fix brackets it may give you enough to go by.

image.png

Reply
Loading...
Highlighted
Junior Contributor

Re: Merbau Decking over concrete slab

Thank you @Brad . 

 

Currently 

 

IMG_20190928_144106.jpg

Reply
Loading...
Highlighted
Community Manager
Community Manager

Re: Merbau Decking over concrete slab

How's it going @Neo19? It would be great to get an update on your decking project. 

 

Please also let us know if you need a hand with anything. 

 

Thanks,

 

Jason

 

See something interesting? Give it the thumbs up!
Reply
Loading...
Highlighted
Junior Contributor

Merbau Decking over concrete slab

Hi @Jason Sorry for this delay. Due to various dramas, it took me a while to finish the deck. Was i completely satisfied with the outcome? May be not, as i rushed towards the end. However learned quite a few things which would be handy when I build the next deck :smile: 

IMG_20191207_141119.jpg

Will it stop leaching tannins at some stage, or should I just oil the deck around two months from conpletion? Started getting some hot days here in western Sydney.

 

Reply
Loading...
Highlighted
Community Manager
Community Manager

Re: Merbau Decking over concrete slab

Many thanks for the update @Neo19. You've done a great job - it looks fantastic. Hopefully it gives you the confidence and experience to know tackle your next project.

 

Most will advise waiting a month or two before you oil the deck for the first time. Here's what Cabots says - https://cabots.com.au/faqs/how-long-do-i-have-to-wait-to-coat

 

Jason

 

 

See something interesting? Give it the thumbs up!
Reply
Loading...
Highlighted
Budding Contributor

Re: Merbau Decking over concrete slab

Hi Neo19

This is best solution I have seen since scouring the web for ideas/answers, i have a similar deck to build over a peeblecrete slab, (deck size 5600mm x 2000mm) slightly running away from the house, and have been a dubious about fixing a ledger board to the brickwork...although the deck area will over hang the slab by about 1.5mtrs

Will post a photo for the area soon.

Thanks for the inspiration.

Cheers

Brendon

Reply
Loading...

Why join the Workshop community?

Workshop is a friendly place to learn, get ideas and find inspiration for your home improvement projects