# Forum Home Renovation Retaining Walls  Attaching deck to retaining wall

## Pickles83

Hi all, newby here  
I am slowly but surely progressing with approximately 25m of retaining wall around our new (old) house.
I am currently running a timber retaining wall (2400x200x75 treated) parallel to our existing deck. The new wall varies from 400mm high to 800mm high. 
I am looking to now extend the existing deck about 1600mm out to the retaining wall and have made it so that the top of the retaining wall will match the height of the deck bearers.
I am wondering if it is ok to attach the new deck bearers to the retaining wall, I am thinking I will screw a bearer along the back of the retaining wall (note i have used the same timber as posts at 1200mm centers) and sit the new deck bearers onto it and leaving about a 30-50mm gap between the end of the bearer and the face of the retaining wall to allow for some movement.  
The whole idea is so that we can walk straight of our deck out onto the lawn and would prefer not to have to put extra. 
I've probably confused everyone else with my explanation although if any have comments they would be appreciated. 
Cheers pickles

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## ringtail

Not a wise thing to do really. The structural integrity of the deck will rely on the bearing capacity of the wall which will, absolutely positively, fail in time. Whack a few steel posts in front of the wall and keep the two structures independent of each other. I gather that the deck is under 1 mt high and if so you can pretty much get away with most things but I would suggest you do it properly. Build it like a chippy, not a landscaper  :Biggrin:

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## Bloss

> Not a wise thing to do really. The structural integrity of the deck will rely on the bearing capacity of the wall which will, absolutely positively, fail in time. Whack a few steel posts in front of the wall and keep the two structures independent of each other. I gather that the deck is under 1 mt high and if so you can pretty much get away with most things but I would suggest you do it properly. Build it like a chippy, not a landscaper

   :What he said:  but . . . properly built is properly built so there is no technical reason why you can't incorporate the structures. The point is that retaining walls are designed and built on an assumption of 'temporary' and 'near enough is good enough'  - and if it moves a little over time then what does it really matter - it'll have shrubs and other things that make it less noticeable and so on. 
A deck might be built that way, but they aren't usually. So to combine the two the build has to be brought up to the deck standard. The increased cost and effort to do so means it's usually best to keep them separate - close and looking 'seamless', but not structurally linked.

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## Smithers

Hi. 
Absolutely nothing wrong with using the retaining wall as support for the deck.  As long as the footings for the retaining wall are a sufficient depth and width to act as a retaining wall and support for the deck.  Tying in the deck to the retaining wall is only going to help stop the retaining wall from moving as it will act as a brace.   
I would think that 600mm deep footings 400mm x 400mm wide would be perfect.

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## stevoh741

x3 for keeping seperate. Connecting deck to wall also creates super termite highway to house. Yeah yeah using treated blah blah blah, they go over timber too so you would need to be vigilant with the visual inspections - easily forgotton over time.....

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## shauck

Also, when the garden bed starts to rot out the retaining wall in several years time, you have a deck connected to it.

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## cherub65

Really to do properly the section where the deck is should be retained in masonry. Joist could have sat on F.L. of block/brickwork.

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## Bloss

> Hi. 
> Absolutely nothing wrong with using the retaining wall as support for the deck.  As long as the footings for the retaining wall are a sufficient depth and width to act as a retaining wall and support for the deck.  Tying in the deck to the retaining wall is only going to help stop the retaining wall from moving as it will act as a brace.    I would think that 600mm deep footings 400mm x 400mm wide would be perfect.

  mmm - I assume this is an attempt at humour? The two comments are contradictory - if the retaining wall is built to do its job properly (and it might or might not need concrete footings at all depending on materials choice and the design) then any notion of 'bracing' from the deck is not a factor. If the deck is to provide any 'bracing' involving horizontal forces from a retaining wall (and both would need to be designed as one structure to meet the different engineering loads), which would not usually be a factor in deck design, then that would be more complex - and costly too. 
Just because you can do some thing is not a reason why you should - in this instance as described by OP the two structures should be separate to do their separate jobs. On another site - then combining a retaining wall and a deck might be the sensible way to go. 
As to footings at that scale for a wall 400mm-800mm high . . . that sure is a lot of concrete  :Eek:   :Confused:

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## Smithers

No humour meant.   
Yes you can look at it as a contradiction, why would the retaining wall need bracing if it was built properly.  Using the deck as a brace is then a bonus it means your retaining wall is over engineered. nothing wrong with that in my eyes.   
The footing sizes I stated would not be over kill considering the posts are 200mm x 75mm and the wall would be used as a retaining wall and and support for the deck.  As a previous poster said, build it like a chippie and not a landscape gardener.

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## ringtail

> No humour meant.   
> Yes you can look at it as a contradiction, why would the retaining wall need bracing if it was built properly.  Using the deck as a brace is then a bonus it means your retaining wall is over engineered. nothing wrong with that in my eyes.   
> The footing sizes I stated would not be over kill considering the posts are 200mm x 75mm and the wall would be used as a retaining wall and and support for the deck.  As a previous poster said, build it like a chippie and not a landscape gardener.

  
Yep, and by that I meant build it properly. Re - reading the OP's first post I get the impression that he wants to secure deck bearers to a ledger that he would fix to the retaining wall. Or, allowing for terminology differences, attach a bearer to the retaining wall like a ledger and then bring the joists out to sit on this ledger with a bit of clearance. Either way, he is not relying on the size of the footings or post holes or the posts for the structural integrity of the deck but rather the bearing capacity and longevity of the horizontal timbers that make up the retaining wall. These timbers, in time, will fail. I have seen on more than one occasion H4 treated sleepers rot in under 18 months and it is for that reason that I suggested a separate line of posts and to keep the two structures independent of each other. A picture or rough drawing from the OP would be most helpful.

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## Bloss

> As a previous poster said, build it like a chippie and not a landscape gardener.

  That was a bit of humour by ringtail ([S]and as he does I am sure, [/S]I know plenty of chippies I would use to build my retaining wall and [S]plenty of[/S] a few landscapers who I would let build my deck)  :Smilie: , but his point for the OP was as mine - build the retaining wall as a retaining wall and the deck as a deck. A well designed and built retaining wall could be built without any concrete footings (depending what materials are used of course) an none of what might be thought of as 'footings' at all. 
To suggest that there is any advantage to combine these too needs is IMO misleading - it would increase costs and the effort required for both structures and the answers I have given, as has ringtail, is to tell the OP that simply bunging in a retaining wall and then attaching the deck to it is not the best way to go. 
What you call 'over-engineering' is nonsense in this context - if the retaining wall is built properly then there no 'bracing' provide by any deck or other structure attached to it. As ringtail says the weak point is the retaining wall - water, soil, roots of plants and a range of other things are more likely to reduce the life (although of course the OP might use interlocking concrete blocks, without footings, that could outlast the house not just the deck!). 
The advice is still the same for this OP - build a retaining wall and build a deck not a combined retaining wall/deck. Of course in other sites the advice might be different.

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## ringtail

To be honest bloss, based on the quality of workmanship I've seen from landscape builders/ landscapers *up here* I wouldn't let one near timber full stop. Paving, block walls and water features seem to be their forte. My brother had 70 k ( yes $70,000) worth of landscaping done by a landscape builder and its absolute crap. I now have to go and rectify all the timber elements and by rectify I mean remove and re build.

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## Bloss

> To be honest bloss, based on the quality of workmanship I've seen from landscape builders/ landscapers *up here* I wouldn't let one near timber full stop. Paving, block walls and water features seem to be their forte. My brother had 70 k ( yes $70,000) worth of landscaping done by a landscape builder and its absolute crap. I now have to go and rectify all the timber elements and by rectify I mean remove and re build.

  I said 'plenty' not all - I'll amend post . . .  :Smilie:

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## cherub65

if that's your opinion of landscape contractors in Brisbane, why would you let your brother spend $70k with one?

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## ringtail

> if that's your opinion of landscape contractors in Brisbane, why would you let your brother spend $70k with one?

  
Not my decision Cherub. Who am I to argue. Not my money and I dont care what he does with his.

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## cherub65

> Who am I to argue.

  
Doesn't sound like you Ringtail, Be interested to see the photos when you get there.

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## ringtail

> Doesn't sound like you Ringtail, Be interested to see the photos when you get there.

    :Biggrin:  I'm not argumentative, much :Tongue:  
Some things they did really well, like stone walls and turfing and a some sandstone paving. Other things like the irrigation system wiring, while probably fit for purpose, looked like it had been done by my 2 year old niece. The timber fencing and gate assembly are the worst though. Timber slats cut with a angle grinder, posts not in line or plumb, gate dropped 50 mm in 1 year, gate out of wind etc... A lot more to the job than this though - exposed agg slabs, water tanks etc... I've already redone the solenoid wiring for the irrigation system and one of their retaining walls and will attack the fence and gate soon.

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