# help with large decking

Hello all,

I am just about to build my first ever decking and I just wanted to check that I am doing the right thing before ordering the materials as this is a large decking.

So the size of the decking is 7.25m long and 3.55m width. The decking will be laid over soil so I will be using posts concreted to the ground to support the frame. I would like the decking to be at the same height as my back door so it flows into the garden. Meaning that the frame will need to be about 20-30cm above the ground and then the opposite end will be about 15-20cm due to a slight incline.

To start I was going to use 100x100mm posts. I will be putting them about 500mm into the ground and using postcrete just add water stuff to secure them into the ground. I was going to have 12 posts in total. The first 3 will be running the width of the house so 3 posts equally divided by the 3.55m width. Then I will put another 3 running parallel at a 2.4m distance from the first 3. Then another row 2.4m from that row and then the last set another 2.4m from the last row equalling 12 posts in total.

Then using 150mmx50mm joists at 2.4m lengths I will make a squared frame around attaching to the outside posts. Then do the same and build a frame around the inner of the outside posts. Once done I will then secure some more joists in a grid like way. I have attached a picture so it will hopefully show what I mean. That will be the main frame built and then I will add my joists in between the frame. Once the frames done then placing the decking down is the easy bit.

On the picture the black squares are the posts, the brown is the main frame and the blue are the joists.

http://s2.photobucket.com/user/danielje ... 4.jpg.html
If the above is ok then I just have a couple of questions.

As you can see from the diagram I have the house and then two fences which makes screwing the frame to the posts a little more difficult. how do I overcome this. I was thinking in using these kind of brackets as this would make screwing everything together a lot easier.

http://www.ebay.co.uk/itm/30-PACK-TECO- ... 337b14e5a2

Or am I going a bit overkill on the frame and maybe just have one frame around the inner of the posts meaning I will have plenty of room and the right angle to screw the joists to the posts.

Would then look like this: single frame around the outside

http://s2.photobucket.com/user/danielje ... B.jpg.html

Heres some actual pictures of the garden. I want the decking to run the full length.

http://s2.photobucket.com/user/danielje ... 7.jpg.html

http://s2.photobucket.com/user/danielje ... 7.jpg.html

Any help will be much appreciated

Regards

daniel
danieljephcott
Rank: Apprentice
Progress to next rank:
0%
Posts: 5
Joined: Tue May 07, 2013 2:53 pm

ok, don't concrete the posts in, make the holes and lay a concrete block or paving slab in the holes.
make your frame away from the fences it will be easier to screw everything together. Then lift it into position, level it, and screw your posts to the frame then concrete around the posts.
welsh brickie
Rank: Project Manager
Posts: 2611
Joined: Sat Apr 12, 2008 7:54 am

that sounds so much better thanks for that.

the only thing that im now debating is how to do the frame. there are so many different ways in doing this im not sure whats best. also how many posts etc needed.

for the size of my decking how many posts would you lay?

i was thinking 3 posts across the width. and 5 rows meaning 15 posts in total.

with the frame would you build the square of the frame then put it in position and then put in the joists.

my last question is the brackets that you can get to hold the joists to the outer frame are they any good. they just dont look like they will support the weight.
danieljephcott
Rank: Apprentice
Progress to next rank:
0%
Posts: 5
Joined: Tue May 07, 2013 2:53 pm

Hi,

Thanks for the reply I think that’s a good idea for the posts to have something solid to sit on and then as you have said concrete them in place once the frame is level and bolted on.

I have been doing a step by step plan for myself and was hoping you guys could have a look to make sure this looks ok and that this would be a strong structure with no bounce.

So any way. As stated above I will dig some holes and use some paving at the bottom of the holes to sit the posts on. in total I will be using 12 posts, posts will consist of 4” square treated posts. As you can see I have spaced the posts 1200mm apart along the width and 1800mm apart on the length. Then using the weed membrane to cover and weigh down with pee shingles.

This will look like this:

Then I will build my outside frame and then carry it over and get it in place and level and then bolt to the posts. I will be using joists for my whole frame. 150mm x 47 mm x 3.6m lengths. Just so I make sure im doing this right my outside frame will be made of 1 x 3.6m on each width and then due to the length being 7.2m I will use 2 x 3.6m lengths and bolt them together in the middle. I was going to do this to join the middles together:

This is what that stage looks like once done:

My next step would be to secure the middle section. For this Im using the joists again and connecting the middle section together and bolting the joists to the posts.

Again check that all is level etc. once that is level I will then concrete the posts in:

Once dried and hard I will then insert the joists. The lengths of joists that I will need will be about 3280mm long. As my width is 3600mm I can have the joists spaced at 400mm centres. Meaning I will need 9 joists down and 3 rows so 27 joists. I was wanting to use the following brackets to secure the joists to the frame:

Then it will look like this:

So im hoping this structure should be strong enough. I did forget to mention that the right side of these pictures will be bolted to the brick of the house using expansion bolts.

My last step is to them secure the decking. Again as the width is 3600mm I will be using 3600mm decking boards. The boards I will be using are 144mm width and 28mm thick. I have worked out that I would need 48 boards with 6mm gaps and it should fit perfectly but would you be able to confirm this for me.

So it should look like this once finished:

Fingers crossed this should be right and I hope I have explained what im wanting to do correctly.

I just want to make sure that what im doing is correct and the structure is going to be strong enough and also my calculations are correct.

Thanks

dan
danieljephcott
Rank: Apprentice
Progress to next rank:
0%
Posts: 5
Joined: Tue May 07, 2013 2:53 pm

with the deck so big build the frame in 2 sections, Hire a nail gun and nail everything together saving the cost of brackets, and with it nailed its solid enough to lift into position.
You can bolt the 2 sections together once in position. nail the posts to the frame when level you can bolt them after, then you can use the nail gun to fix the planks
welsh brickie
Rank: Project Manager
Posts: 2611
Joined: Sat Apr 12, 2008 7:54 am

Or it could be done in 3 sections.

So does this seem up be strong enough?
danieljephcott
Rank: Apprentice
Progress to next rank:
0%
Posts: 5
Joined: Tue May 07, 2013 2:53 pm

it can be done in as many sections as you want, and your plan looks good
welsh brickie
Rank: Project Manager
Posts: 2611
Joined: Sat Apr 12, 2008 7:54 am

So will it be ok laying 3.6m long decking straight on top of that frame. I've seen a lot of comments about staggering but my 3.6m decking will fit perfectly in a row
danieljephcott
Rank: Apprentice
Progress to next rank:
0%
Posts: 5
Joined: Tue May 07, 2013 2:53 pm

no that's fine
welsh brickie
Rank: Project Manager
Posts: 2611
Joined: Sat Apr 12, 2008 7:54 am

Display posts from previous
Sort by
Order by

• DIY How to Project Guides
• DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

• Related Topics