Decking sub frame help.

[roadrunner45]

Hi All,

I am planning to build a storage area behind my garage (1 metre wide by 2 metres long) with a small decked area to improve access as just uneven ground at present and maybe overhead shelter to keep the worst of the weather out.

The challenge I have is that the sub frame planned will only be supported by 2 walls with a cross brace and my concern is will it be strong enough to support me walking on occasionally, without supporting in the top left area on my sketch attached and if not strong enough any ideas of how I can add additional support?

Thanks again for your help.

 

[Jameshow]

Can you not put a post in the far left corner something like a fence post? Then hanger your joists into it. It will then support the roof too? Cost about £10.

 

[Bingy man]

Why not fix a joist just in front of the fence , a breeze block at each end and 1 in the middle laid on a little concrete pad . Ideally a 2nd joist between the fence and your house wall would illuminate any bounce between the deck boards. You could then do away with the angled brace . You could also achieve the same results using sleepers . 3 - 1 each end and 1 in the middle levelled out will give you a rock solid base for your deck boards- you could do this freestanding and simply fix the deck boards to the sleepers as long as said sleepers are firm and level imo ..

 

[Hypnotic Chimera]

Why not fix a joist just in front of the fence , a breeze block at each end and 1 in the middle laid on a little concrete pad . Ideally a 2nd joist between the fence and your house wall would illuminate any bounce between the deck boards. You could then do away with the angled brace . You could also achieve the same results using sleepers . 3 - 1 each end and 1 in the middle levelled out will give you a rock solid base for your deck boards- you could do this freestanding and simply fix the deck boards to the sleepers as long as said sleepers are firm and level imo ..

Good idea. As long as the sleepers are the used proper oil tar/creosote ex railway sleepers. Those last for decades unmaintained.

Personally, I'd sink three cut sections of one post, cut down to appropriate size, into post holes in the left hand side, secured using postcrete. Then fix the left hand end beam/joist to those.

 

[roadrunner45]

Good idea. As long as the sleepers are the used proper oil tar/creosote ex railway sleepers. Those last for decades unmaintained.

Personally, I'd sink three cut sections of one post, cut down to appropriate size, into post holes in the left hand side, secured using postcrete. Then fix the left hand end beam/joist to those.

Thanks for the advice , I will use the cut down post option, I have never used postcrete but hopefully straight forward, let me know if you have any tips using postcrete.

 

[Bingy man]

Thanks for the advice , I will use the cut down post option, I have never used postcrete but hopefully straight forward, let me know if you have any tips using postcrete.

Yes don’t add any water untill everything is level and true . Then just add a few cupfuls and nature will do the rest . A couple of bags should do 3/4 posts as it’s not like your erecting a 6’ fence ..

 

[Hypnotic Chimera]

Thanks for the advice , I will use the cut down post option, I have never used postcrete but hopefully straight forward, let me know if you have any tips using postcrete.

Exactly what Bingy man said above.
Other tips would be to place post in first before the concrete mix and support/fix the post in some way so that it doesn't move when adding the mix.
I have dug holes a little bit deeper and put some hardcore in the bottom so that the end of the post is not in direct contact with soil.
I then use the post to pound the hardcore down a bit to bed it in. Using this method you can add hardcore gradually until you get the post at the level you want, and it usually creates a level base for the post so you can take your hands off and it remains upright.
Which leads to the next point... if you're going to use the posts to fix a support rail, I would screw in the support rail to the propped up posts and align the entire sub-structure and support that with something prior to putting in the mix. For short cut-off posts, you probably only need a bag per 2 posts. You could probably get 4 stub posts out of a single 3"x3" decking post and use 2 bags of postcrete.

Once the sub structure is where you want it, only then fill the holes with the mix.

Make sure you fill the holes to the soil level so that you're not creating a basin where water will pool and rot the post prematurely.
Even better - angle the postcrete mix upwards to the post base - this will ensure water will definitely not pool around the post base, this is what I did with my deck build earlier this year. The posts were all aligned and fixed to a temporary beam prior to filing hole with the mix, and this photo is a few steps later in the build but you can see the angling of the powder mix and that the previous temporary structure held them in a good alignment:

One thing I would definitely recommend is a post spade. Two reasons - first they make the job far, far easier and quicker, because they dig holes better. It's a game changer, really; second, being narrower and longer, you can control the size of your post holes - and for your project you definitely benefit from post holes not being too big - it'd just be a waste of postcrete.

link: screwfix

 

[Bingy man]

Exactly what Bingy man said above.
Other tips would be to place post in first before the concrete mix and support/fix the post in some way so that it doesn't move when adding the mix.
I have dug holes a little bit deeper and put some hardcore in the bottom so that the end of the post is not in direct contact with soil.
I then use the post to pound the hardcore down a bit to bed it in. Using this method you can add hardcore gradually until you get the post at the level you want, and it usually creates a level base for the post so you can take your hands off and it remains upright.
Which leads to the next point... if you're going to use the posts to fix a support rail, I would screw in the support rail to the propped up posts and align the entire sub-structure and support that with something prior to putting in the mix. For short cut-off posts, you probably only need a bag per 2 posts. You could probably get 4 stub posts out of a single 3"x3" decking post and use 2 bags of postcrete.

Once the sub structure is where you want it, only then fill the holes with the mix.

Make sure you fill the holes to the soil level so that you're not creating a basin where water will pool and rot the post prematurely.
Even better - angle the postcrete mix upwards to the post base - this will ensure water will definitely not pool around the post base, this is what I did with my deck build earlier this year. The posts were all aligned and fixed to a temporary beam prior to filing hole with the mix, and this photo is a few steps later in the build but you can see the angling of the powder mix and that the previous temporary structure held them in a good alignment:

View attachment 191719

One thing I would definitely recommend is a post spade. Two reasons - first they make the job far, far easier and quicker, because they dig holes better. It's a game changer, really; second, being narrower and longer, you can control the size of your post holes - and for your project you definitely benefit from post holes not being too big - it'd just be a waste of postcrete.

View attachment 191724

link: screwfix

In addition to this spade which makes sense is a manual auger. I’ve got a 4” and a 6” and depending on the ground makes short work of post holes , you will need at least 3 weetabix though as winding it in will give you a good workout. I use similar as above but use a post hole digger to remove the soil . What I have found over the years as I’ve got older is the better your digging tools the less back pain you end up suffering.. a really good shout to use hardcore or gravel under the posts ..