Ask a question

The Bunnings Workshop community can help with your home improvement projects.

How to build a garage to wall lean to?

Finding My Feet

How to build a garage to wall lean to?

Looking to build a lean to from my garage roof to my brick wall. Currently the area has no drainage and floods during winter, I would also like to close up the area.

Any tips on materials etc would be appreciated. 

Roof to wall 125-130cm 

Length of garage roof to connect 320-330cm 




Amassing an Audience

Re: Tips For Garage To Wall Lean To

Hi @Corey1,

Welcome to Bunnings Workshop, Thanks for coming here!

When you say that the area floods during the winter, how does that occur?

Is it because of the spouting on the side of the building overloading with water or is it because of other issues like a blocked spouting or down-pipe?

Before you add a lean-to over the area, you need to sort this issue out, because with adding more roof area (with the addition), this will

add to the catchment area of the roof, whereas the rain that would have normally fell on the ground, will fall on this new roof/ spouting system

and you do NOT want the rainfall from your lean-to spilling over into behind that retaining wall, that will eventually cause it to collapse, suddenly.

Let me know what is going on there and we can work out some sort of a plan.



Mike T.

Re: Tips For Garage To Wall Lean To

Hi Mike, 

It's an older house with the garage being an extension. There is no down pipe on this side of the roof and so when it rains it will overflow and due to the area below being concrete there is no drainage or area to insert drainage. The other side of the wall is a garden bed and so my thought was this would be okay for the extra water? If that is not the case what other recommendations would you consider? 

Amassing an Audience

Re: Tips For Garage To Wall Lean To

Hi @Corey1,

To my way of thinking, you need to sort out the issue why there is not any storm-water drainage on that side of the building.

and that is that in a nutshell with respect to your flooding issues.

The person that installed that spouting/ storm-water system should have installed at least (from looking at it) 2 down-pipes and a collector at ground level.

You can't hope to drain away rain water with no down pipes at all, it just doesn't work like that.


Mike T.


Re: Tips For Garage To Wall Lean To

Hi @Corey1   and @MikeTNZ 

Corey1   can you  take pics of closest  down water  pipes and try to angle photo back to your desired shelter area so we have  some photo context.

Mike is right your first probem is increasing storm water handling. Dont want  scare you if you dont those  over  flows can  end up  water logging you house eves and more.


Mike I am thinking closest down pipe is on the house  not seen on photos between the garage and house,  that photo of house side not showing standard external down piping is there  other types?


Got to cut concrete to get more  storm  water  drains in ?




Re: Tips For Garage To Wall Lean To

Hello @Corey1


Allow me to welcome you as well to the Bunnings Workshop community. It's a pleasure having you join us, and thank you for sharing your question about your garage.


It's great that you've received fantastic advice from @MikeTNZ and @Jewelleryrescue. I agree with their assessment of your situation, it seems that your gutter overflow is being caused by a lack of downpipes at the side of your garage. Is your garage floor totally level or does the water tend to pool in one area only? Does it drain away or does it evaporate over time? This might have to be addressed as well. 


Would it be possible for you to post a complete photo of that area including the garage floor? Having the water drain away properly is very important as water can erode soil and cause damage to walls and house foundations.  


In regards to closing the area,  I suggest having a look at the rules and regulations of your local council regarding linking your roof line to your brick fence. 


If you have any other questions we can help with, please let us know.




See something interesting? Give it the thumbs up!

Re: Tips For Garage To Wall Lean To

Hi @EricL 


Water around  houses like hot water  over flows leaky down pipes wet and soften the soil  and mud can be made more easily in the soil and can lead to termite nests forming.    Know your enemy lol

Amassing an Audience

Re: Tips For Garage To Wall Lean To

Hi @EricL,

The design and installation of proper storm-water removal from a house, no matter how large the roof is, depends on the following


  • All of the spouting installed around the perimeter of the building has "fall" to a down-pipe.
  • From the opposite end of the property to the front gate, there will be fall of between 2.5 to 3.5 degrees over the distance that the spouting travels.
  • This needs to be worked out before the spouting brackets are installed, with either a chalk-line or a continuous laser while those are fitted.
  • Where water, for whatever reason turns corners, there should be a down-pipe on that corner to prevent turbulence and lack of draining during high rainfall.
  • All down-pipes require a collector at their base of 200% of the size of the down-pipe feeding them, to save air-locking and flooding during heavy rainfall.
  • Make any down-pipes as large as possible and bracketed well.
  • All spouting should be covered with mesh to keep leaves and the like out and prevent blockages.

Re: Tips For Garage To Wall Lean To

Hi @MikeTNZ 


1 Looking at you notes  I dont have  the outlets near the corners and I think i  might retify this.


2 I have never  seen a 200% collector  in Australia  maybe that factor is built into down pipe  diameter specifications (And  noted as large as possible)


Mesh  thats a later  problem I plan on meshing under  fisrt tile to gutter outer edge  to let leaves  land and blow off no  trap pionts.  Hardest part is the roof  V  joins will have to mesh all the way up.

I also got to say  my roof guttering installer didnt bother to add  any down angles at one spot i had to add a drill  a hole to drain water to stop mosquitos.  


Ok I am starting to se a full rebuild thats  going to cost a bomb. 


Why join the Bunnings Workshop community?

Workshop is a friendly place to learn, get ideas and find inspiration for your home improvement projects