Hi,

I'm in the process of building a circular deck area in our garden. It comprises a deck area just over 3m in diameter set inside a double concrete block (440x215x100mm) wall with a 240mm "cavity" between the walls which will be used as a planter. I've already laid concrete foundations for the walls and my plan is to set the deck at the level of the first block course and then build another two courses above that for the planter. The planter will extend to about 270 degrees with an open section to step down from.

What I would like to know is if anyone here has good or bad experiences with composite decking? I would very much like to make the whole deck "maintenance free" besides cleaning the surface and maybe painting the rendered block walls every few years and tending to the plants.

I've built decks before using wooden framing and decking, and it's always nice to begin with but as it weathers you get splits and knots fall out plus it tends to get slippy from algae deposits requiring regular cleaning and treatment. So I like the idea of using an engineered material which should remain more structurally stable over time and shouldn't rot etc. I am aware the mould can be an issue if you don't clean it off immediately and I've heard other random complaints about decking boards getting soft and bouncy, but in general I have seen more positive comments than negative ones.

So, given that I am suspicious of online reviews and have considerably more faith in the options of folks on this forum, what advice would you offer? The company I'm thinking of using is https://www.dinodecking.co.uk

Thanks everyone,
Craig.

ps. I tried to post a photo but the uploader is throwing a MYSQL error still.

[Edited on 10/9/2020 by craig1410]

I've just finished a deck and went through the same processes.

Best advice I can give is get some (free) samples online. I tried a few and found that they all scratched easily and with two dogs I thought it'd look rubbish within a few months. They'd be perfect for normal footfall though. I have seen some of the composite stuff split when frozen, but I think this mainly applies to the cheap lengths with channels that run through them.

Personally, I went for a hardwood deck in the end, Yellow Balau and it looks great, cost about the same as composite. Yellow Balau, when oiled should last 25 years, or can be left to grey. Another good hard deck (although actually a softwood) is Siberian Larch, but I found it difficult to source locally.

I also used concrete decking posts that have a notch out of the top for the joist to sit on and a bolt hole, I used c24 timber and stainless steel bolts which should put a stop to any rotting of the frame.

I'd be interested to hear others thoughts on this as its something I'm contemplating to. there was a discussion on pistonheads this year: https://www.pistonheads.com/gassing/topic.asp?h=0&f=&t=1867441

on that piston heads link there was a mention of porcelain tiles as an alternative to decking. https://alfrescofloors.com/

paul

[Edited on 11/9/20 by swanny]

Hi,
Thanks for the ideas, I hadn't thought about tiles, but it might be a bit tricky in my case since the deck is to be circular and I'm not sure I fancy trying to cut all those tiles.

Hardwood is certainly worth consideration and was something I did think about but wasn't sure how easy it would be to get the materials. I was also worried about the frame rotting because I built a deck back in 2007 and even though the wood was "guaranteed for 15 years against rot", it only lasted about 7 years before I had to rip the whole thing up and replace it. The second time around I bought the wood from Wickes instead of B&Q and I soaked the frame with some VOC based clear preservative. That formed a waxy layer when it dried off and caused the water to bead off the surface nicely. That second attempt was still looking very good when we sold the house last year.

I'll certainly look into the hardwood option because I do like working with wood and don't mind a little bit of maintenance such as cleaning, oiling or preserving. I just don't want to have to replace the frame every 5-10 years if I can avoid it. I think I used C16 joists last time but will consider C24 this time as it has a tighter grain and fewer defects from which rot might start. For under the joists I was planning to just use something like an engineering brick bedded into a shovel full of concrete since I don't need much height.

Keep the ideas coming please

Thanks,
Craig.

C24 won't be any more rot resistant than C16. C24 is generally used for overhead joists with long spans. I built a large deck two years ago and build decks occasionally at work. In my experience properly pressure treated softwood timber will last a very long time. Buy it from a timber merchant rather than a DIY store. Make sure there is plenty of airflow around frame under the deck. If using wooden posts then I have have good results with 'Post Savers'. Make sure the concrete allows rain to flow away. Don't let any part of the frame touch soil. Also use end grain preservative on every cut. I dug up a offcut of pressure treated decking the other day. It looked really old. However the sides, top and bottom were okay, the ends were scalloped inwards 2 inches with rot. It was a great example of why pressure treating works.


I scrub, pressure wash and add new preservative to mine every year on top of the pressure treatment. Seems to be okay.

Sorry. I don't know much about composite decking. However when I looked into it, it seems to be at least double or triple the price. If good quality pressure treated softwood can last ten years. Then composite decking needs to last 30 years at triple the price. By that time I'll have moved out!

When I did mine I thought about the joists getting wet in the gaps of the decking, and the water being stuck next to the decking. I put a damp proof membrane down on top of the joists. No idea yet if it's a good idea or not as it's only been 5 years.

Hypochloride is the answer!!

Not to your question to be fair but it resolves the issues with slippy softwood decking. Hypochloride is cheap as chips because the dairy farmers use it in great quantities. I pay £14 for 20 litres from the dairy suppliers there are loads around you.

It's diluted 5:1 so that's 100 litres for your dosh and it kills everything it touches including COVID - well it would 'cos its industrial-strength bleach.

Well known amongst house developers, spray it on external walls and they look like new, kills weeds and small children with impunity!

I have extensive decking and this stuff solved the algae and slime issues with a yearly application - it also gives that sun-bleached look thats so hard to get. Been using for 5 years with no issues.

Happy framing

@MikeR yeah, I also thought about doing what you've done with some DPC strips along the joists to direct water away from them but I worry that the plastic will tend to hold water against the wood and not let it dry out. I think it would probably be fine though.

@Irony I realise C24 isn't necessary for this application although having that extra strength might allow fewer points of contact with the ground while providing the same solid feel. Plus fewer defects, knots, potential split points etc can't be a bad thing. Agreed on going to a timber merchant and the various other tips you suggested. On my second deck attempt I made sure any cut ends were soaked in preservative by pouring the stuff into an old ice cream tub and propping the pieces of wood against a wall with the ends in the preservative for a few minutes before putting them in place. It's surprising how much gets sucked in.

Re pressure washing - this is one thing I would NOT recommend unless you back the pressure off. I strongly believe pressure washing our first deck was the main reason it rotted. What we did with the second attempt was use the decking cleaner from B&Q which removes the algae with nothing more than a deck brush and a garden hose. It really works well. (This: https://www.diy.com/departments/ronseal-clear-decking-cleaner-reviver-5l/127170_BQ.prd )

@v8_kid good tip - will certainly look into that.

[Edited on 11/9/2020 by craig1410]

quote:

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Originally posted by v8kid
Hypochloride is the answer!!

Not to your question to be fair but it resolves the issues with slippy softwood decking. Hypochloride is cheap as chips because the dairy farmers use it in great quantities. I pay £14 for 20 litres from the dairy suppliers there are loads around you.

It's diluted 5:1 so that's 100 litres for your dosh and it kills everything it touches including COVID - well it would 'cos its industrial-strength bleach.

Well known amongst house developers, spray it on external walls and they look like new, kills weeds and small children with impunity!

I have extensive decking and this stuff solved the algae and slime issues with a yearly application - it also gives that sun-bleached look thats so hard to get. Been using for 5 years with no issues.

Happy framing

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quote:

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Originally posted by craig1410
@MikeR yeah, I also thought about doing what you've done with some DPC strips along the joists to direct water away from them but I worry that the plastic will tend to hold water against the wood and not let it dry out. I think it would probably be fine though.

@Irony I realise C24 isn't necessary for this application although having that extra strength might allow fewer points of contact with the ground while providing the same solid feel. Plus fewer defects, knots, potential split points etc can't be a bad thing. Agreed on going to a timber merchant and the various other tips you suggested. On my second deck attempt I made sure any cut ends were soaked in preservative by pouring the stuff into an old ice cream tub and propping the pieces of wood against a wall with the ends in the preservative for a few minutes before putting them in place. It's surprising how much gets sucked in.

Re pressure washing - this is one thing I would NOT recommend unless you back the pressure off. I strongly believe pressure washing our first deck was the main reason it rotted. What we did with the second attempt was use the decking cleaner from B&Q which removes the algae with nothing more than a deck brush and a garden hose. It really works well. (This: https://www.diy.com/departments/ronseal-clear-decking-cleaner-reviver-5l/127170_BQ.prd )

@v8_kid good tip - will certainly look into that.

[Edited on 11/9/2020 by craig1410]

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Back to the original question, a friend has just replaced his old wooden one with Ecodek, apparently you can buy the lenghts you need as its extruded so waste is minimal. So far he's pleased with it and probably won't be around when the 25 year guarantee runs out!

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Originally posted by joneh

quote:

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Originally posted by craig1410
@MikeR yeah, I also thought about doing what you've done with some DPC strips along the joists to direct water away from them but I worry that the plastic will tend to hold water against the wood and not let it dry out. I think it would probably be fine though.
[Edited on 11/9/2020 by craig1410]

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It's pretty easy to google a few horror stories about using plastic between the joists and boards, so I'd check that out. I should have mentioned is used C24 for a long span over a pond! I wouldn't recommend jet washing decking either.

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Originally posted by MikeR

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Originally posted by joneh

quote:

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Originally posted by craig1410
@MikeR yeah, I also thought about doing what you've done with some DPC strips along the joists to direct water away from them but I worry that the plastic will tend to hold water against the wood and not let it dry out. I think it would probably be fine though.
[Edited on 11/9/2020 by craig1410]

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It's pretty easy to google a few horror stories about using plastic between the joists and boards, so I'd check that out. I should have mentioned is used C24 for a long span over a pond! I wouldn't recommend jet washing decking either.

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Could you provide some links, I've only found one reference & yet have found a few companies who sell stuff to motor what I've done

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That's very different to the suggestion. That's a fabric that will hold and channel water. I'm referring to a small bit of plastic that water will run off. I also have gravel on the floor with a large air gap.

I'm curious if you have any more but let's do it via u2u to stop the post hijack
.

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Just had a look for this and Sodium Hypochlorite comes up - is this what you mean?

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quote:

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Originally posted by MikeR
That's very different to the suggestion. That's a fabric that will hold and channel water. I'm referring to a small bit of plastic that water will run off. I also have gravel on the floor with a large air gap.

I'm curious if you have any more but let's do it via u2u to stop the post hijack
.

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I just wanted to wrap up this thread (famous last words... ) by saying thanks to all who gave advice and experiences.

I'm pretty sure I'm going to go with smooth sided Yellow Balau hardwood decking on a traditional timber frame, probably using C24 joists on 450mm centres sized appropriately to avoid the need for a centre support across the 3.2m span. Not sure if 4" x 2" would be sufficient but I'm pretty sure 6" x 2" will be more than enough.

I'll support the ends on half breeze blocks cemented to the main structure. The blocks are porous and should avoid any puddles remaining around the joist ends. I'll also dip each sawn end in preservative and coat the frame liberally a couple if times before attaching the boards. I might even squirt some preservative into the screw holes between drilling and screwing in the stainless screws. I might look into using hidden fixings too.

Lastly, I intend to oil the deck each year as I'm not a massive fan of the faded look. Will also keep in mind the idea of applying sodium hypochlorite to suppress algae if that becomes a problem.

Will try to post some pics of the finished project if I remember. I'll probably not install the deck until the spring now but will try to get the blockwork and framing done so it's ready to accept the boards.