Deck Job

7 Jun 2020
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United Kingdom
I’m a complete novice at DIY and have taken on a bit of a largish deck job at the rear of my property. I moved most of the existing concreted patio and the deck frame is now larger than the concrete patio was. Deck frame is 50x150mm pressure treated timber. I’ve kept a partial amount of the previous patio to hold up the frame and the remaining three sides I’ve put 50mm concrete paving slabs at intervals of every 1.5m. My question is as it was meant to be a ground deck and then subsequently has turned into a low level deck should I have put posts in between to hold up the structure more? After realising my mistake I’ve put more concrete paving slabs under but not secured in by any means. Have a look at the pictures and all feedback is welcome.

Thanks, Rick


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Im hoping to lay timbertech composite decking, and also the square space that looks like it’s not been filled yet is going to be a inspection hatch for a man hole cover :)
Hi Rick, I have just completed a decking which ended up raised as the garden slopes. My only concern would be that over time the slabs may sink if they are just laid on was was the lawn also have you made sure water will run away from the house? Looks like you are higher than the dpc.
Thanks for the reply, Marc yes there is a fall of about 25mm from house to front of deck. I have built above the DPC only because when I got companies to come and look and quote they said they would lay over the existing broken patio which is not far off the DPC height, I’ve buuilt the frame approx 10mm from the brick of the house, is that suitable? Also when you built your frame did the joists line up perfectly? I have a few that are higher and lower than most of the ones I’ve put in, I assume it’s because they have warped slightly etc. Regarding the sinking of the slabs what would you assume I do next? Unlikely they will move too much though as the previous patio had been there about 60-70 years apparently. Solid Solid ground surrounds the house after I did the fence last year!
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Morning, the 10mm should be fine you just don’t water sat against your brickwork as long as it can escape should be no problem. I fixed posts into the ground using 100x100 fence posts some where only 300mm above ground and I fixed my frame to these, you could remove the slabs and lay some concrete footings it just depends on how solid the ground is. I don’t have any pics of mine in progress. As for the joists I feel your pain about them being warped makes life difficult, most of the joists were level and the ones that weren’t were near enough the boards went down fine I was using wood though not composite.
Hey Marc, ok I’ve decided to bite the bullet and remove some of the slabs and attach about 10 support posts keeping around a distance of about 1.5m between them, how deep did you put yours into the ground/how deep would I need to dig? I know conventionally your supposed to use 100x100 posts but as I’ve got loads of the pressure treated timber left (150x50) from the frame do you think I could get away with using that instead?
Hi Rick, can’t see it being an issue just remember to treat the cut ends of the timbers. I tried to get mine the same length as above the ground or at least 300mm and it’s solid other sites said 700mm! But mine and looking at yours its only raised one step height rather than a true raised deck. At the bottom of my holes I put some sand to help level first then cut some old paving slabs so the posts wasn’t in contact with the soil and had a bit of a base. Then just used quick drying post concrete set in about 10mins.
I made the post higher rather than trying to get them exact then just cut off level with the joists.
Thanks Marc, I think I’m gonna use proper posts just as there thicker just incase they do start to rot over time, I’ve measured the distance from floor to bottom of joist and it’s only 100mm!! So definitely don’t think I’ll dig too 700mm. Will most likely dig to your guide of about 300mm below ground! Will also use your method of cutting them off once fixed in! Did you use bolts or screws for the post fixings? Your pics look really good!! Looks like a solid deck and family look like they enjoy it too!!
Hi Rick, sorry for the delay had lots on at work! I used screws lots of them was a bit concerned but I’m happy it’s solid and not going anywhere the rest was the hot tub and it’s held fine. Just need the weather to change now to get out there!
I used these to screw the boards down worked really well and saved loads of time.
Thanks for the help Marc. Have added some posts, for extra support, my deck boards arrive next week so fingers crossed it gets finished soon!
Hi Rick, hope all is well with the deck post some pics when you’re finished in this heat you will be ready for a beer or two!!

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