We have an “L” shaped garden and have decided to patioify the l bit to create a rectangular lawn and rectangular sitting area. This will be around 3.3m x 2.4m. We did mull over flagging/paving but it looked like a heck of a task getting the sub-base stable. So a low deck has been contemplated, standing around 4-6” above the adjacent lawn..
I have built an elevated deck before that stands on four hefty legs, then double 8x2 cross members supporting the frame work.
Low level decks seem to need much less structural support but I can’t decide between laying a gravel bed and just sitting, say a 4” x 1.5” Frame on this......or sitting same frame on concrete breeze blocks to lift if it the ground and letting air flow underneath.
To add a bit if faff, we are also looking at a gazebo/pergola type structure so somewhere in the framework, there will need to be four sturdy uprights. Should I postcrete these into their own holes and also bolt to the frame, or just bolt to the frame, or even use those metpost concrete mounts to maybe get the best of both worlds (concrete security but clear from rot etc).
And also, the uprights will be for climbing plants so I’ll need some “soil” around the base of the posts and a hole in the deck to allow it to grow and climb through.....
Thoughts and ideas welcomed as there seems to be conflicting advice online.
We’ve just built pretty much what you’re describing.
Built the pergola first with the 4 posts postcreted in.
[url= https://i.ibb.co/8Xh06S5/6674-C3-A9-8-D8-B-427-D-81-E9-C502406397-D5.jp g" target="_blank">https://i.ibb.co/8Xh06S5/6674-C3-A9-8-D8-B-427-D-81-E9-C502406397-D5.jp g"/> [/img][/url]
Then started laying out the framing fixing it to the pergola posts to get a square & level starting point.
[url= https://i.ibb.co/T2ZQtrz/46-C4318-C-E2-D4-42-C1-8-A1-E-E59-E6-BDD4914.jp g" target="_blank">https://i.ibb.co/T2ZQtrz/46-C4318-C-E2-D4-42-C1-8-A1-E-E59-E6-BDD4914.jp g"/> [/img][/url]
Finished frame, 50mm centres for joists.
Postcreted in lots of short 75mm posts.
[url= https://i.ibb.co/jfzDMPk/40-FFBD65-A559-4129-9541-CF20-A03-BF8-E0.jp g" target="_blank">https://i.ibb.co/jfzDMPk/40-FFBD65-A559-4129-9541-CF20-A03-BF8-E0.jp g"/> [/img][/url]
Built the deck.
[url= https://i.ibb.co/P9gsSm8/C16822-B7-92-B0-4153-AE4-B-DE0-DAA08-B820.jp g" target="_blank">https://i.ibb.co/P9gsSm8/C16822-B7-92-B0-4153-AE4-B-DE0-DAA08-B820.jp g"/> [/img][/url]
The deck is 4.8 x 3.2
We’d never done it before, so may not have been the best way but it’s solid with no bounce. I put all the support posts in after I’d built the frame, supported only by the 4 pergola posts, by levelling it with blocks and then digging the holes and creteing them in. It ended up very level but if I was doing it again I think I’d put the posts in as I went along. The joists are only 100x50, I wanted to use 125 or even 150 but didn’t want to raise it any higher.
As I say, no expert, but very happy how it turned out.
Good job.....Thanks for taking the time to post.
Are the pergola posts wrapped in fabric or something as they look black where they enter the ground?
What do you mean by preferring to put posts in as you went along, the pergola posts or the little 75mm supports?
No, I painted them with bitumen paint after they were fitted. Tbh don’t think it was worth it.
Would probably be worth doing them before putting them in the ground if anything. They’re 150mm posts so reckon they’ll take a fair few years to rot. At least I hope so.
Are the pergola posts wrapped in fabric or something as they look black where they enter the ground?
Might be Postsaver sleeves, if not those still worth a look for your project.
https://www.postsaver-shop.co.uk/
If you go with 400-500mm joist spacing you can rest your joists on 600x600 paving slabs (spaced appropriately) and each slab will do 2 joists. You could also add plastic wedges or risers to get the levels exact and minimise the contact the joists have with the slab
What do you mean by preferring to put posts in as you went along, the pergola posts or the little 75mm supports?
The support posts. I started with 2 joists across each end attached to the pergola and then put the 2 long joists along the outside edges, I should have put the supports in as I put those ones on. Then when I put all the joists in across ways the outer ends of each one would have been supported.
The whole thing sagged a couple of inches as I built it and I then had to jack it back up when putting the posts in. Like I say I got rid of all the sag but probably wasn’t the easiest way.
Would have save the monotony of digging all 30 holes at once too!
I did a similar project minus the pergola and used these which were a real time saver: https://www.jouplast.com/l-en/139/decking-products.html
I built a raised deck 4.8m by 3m some 11 years ago. Used 4x4 post to raise the deck off the ground some 30cm.
Posts where concreted in bit put plenty of gravel underneath,so they weren't going to sit in too much damp.
I took some of the decking boards up this summer for a looksy and was surprised at little sign of rot I found on the bearers and posts looked ok.
For me the biggest thing is to ensure the deck was angled for run off, so the water doesn't pool.
If I was doing it again I would look at plastic lumber posts or those post jacket things. Oh and I would bitumen paint the bearers for good measure.
I'd do what Phil has done.
For me the biggest thing is to ensure the deck was angled for run off, so the water doesn’t pool.
Mine falls 10mm per metre so 50mm from one end to the other. You can’t tell at all so I’d be tempted to go for slightly more of a slope if I did it again. Although it seems to drain well, we’ve had some proper rain today to test.
Certainly agree with the angle for run off. Mine runs off into the trees behind my house. My neighbour didnt do this and his just pools water and hes had to replace a number of joists due to rot (built the same time)
I would also just use decking oil from the outset rather than stain.
Had good results using the Screwfix No frills stuff. I've had it for 18quid a tin when the offers are on