How to fix leaking in garage?

[ChrisA]

Hi everyone,

I have an old garage that I want to convert to a music room with lots of equipment. It has hardiplank on the outside and I plan to add acoustic insulation it and then add thick soundchek plasterboard for sound proofing.

My problem is that some water gets in at the bottom of the walls in heavy rain and I wanted to make sure this was fixed before starting work on the room.

On the advice for a local plumbing store I installed a down pipe and a stormwater pit which goes to a pit of blue metal…but this overflows in heavy rain. (please see pics)

My question is should I install some type of drain around the garage before doing the project and if so what type.

Also should I try to waterproof around the bottom of the walls?

As you should be able to see I. The fourth photo the fence is higher than the bottom the shed and the land slopes down.

I would be grateful for any help/ suggestions.

 

 

 

 

   

  

[JacobZ]

Hi @ChrisA,

Firstly, welcome to the Bunnings Workshop community, it's great to have you join us.

From your provided photos, there are a few things you can do to promote better drainage and stop the water ingress.

You should look to have some agi pipe installed around the perimeter of the garage to capture any water flowing into the area from the surrounds. This is likely something you should employ the services of a professional plumber for as they could connect the agi pipe into your drainage pit and your drainage pit into a stormwater pipe so the water flows away to the street.

You should also bring the height of soil around the garage down by around 100mm and backfill with 10-20mm Drainage Gravel which can also  be ordered in bulk bags from your local stores Special Orders desk . This, in combination with the agi pipe, will allow the water to flow away from the concrete slab more effectively.

Finally, you should use Sikaflex 11FC Plus Polyurethane Adhesive Sealant to seal between the concrete slab and the bottom plate of the garage. This will create a physical barrier preventing the waters entry to the garage.

Please feel free to get in touch if you would like more advice or product recommendations.

Jacob

[ChrisA]

Hi Jacob,

Thank you very much for your recommendations…they sound really good.

Just wanted to ask how wide and deep you think the drainage trench needs to be …also should the trench be right up against the shed or should there be a gap?

Also I was thinking of making a trench a French drain with the gravel on top …would that work? 
Thanks again for your suggestions.

Regards 

Chris

[JacobZ · Accepted solution]

Hi @ChrisA,

A french drain would be great for this situation but they can mean a lot of digging. You should aim for the french drain to be around 100-200mm wide and around 200mm deep with slotted agi-pipe at the bottom and gravel on top. You should also ensure the agi pipe gently falls towards the drainage pit.

Have a look at this helpful article, How to install garden drainage, for some guidance.

If you are planning to dig a french drain, it will also be beneficial to install Corflute up against the slab to cover the gap between the bottom plate and the concrete and extending down below the slab. You could then seal the top edge of the corflute using the beforementioned Sikaflex 11FC, creating a solid physical barrier preventing water from getting in.

Let me know what you think.

Jacob

[ChrisA]

Hi Jacob,

Thank you for the ideas.

So just to confirm the trench will be right up against the side of the garage and all around the the three sides?

Also when you say drainage pit what are you referring to …making a pit for the water?

Finally when you refer to a bottom plate what do you mean?

Sorry for all the questions!

Thanks again!

Regards 

Chris

[JacobZ]

Hi @ChrisA,

No need to apologize for the questions, that's why we're here.

1. Yes, the trench should run close to the garage and around all three sides. If it's not close enough to the concrete slab, it will allow an area for water to pool.

2. When I'm referring to the drainage pit, I mean the "stormwater pit" that you've mentioned you installed on the advice of a local plumbing store. It is visible in photo 2 & 3. 

3. When I refer to the bottom plate I mean the horizontal timber member at the bottom of the stud wall. I have circled it in the below photo.

 

If you have any other questions, please get in touch.

Jacob

[ChrisA]

    

Great thanks Jacob much appreciated…that clears a few things up.

 So you are suggesting to glue the corn flute to the beam at the bottom ..but that is covered by the hardiplank…that’s why I was confused.

I also discovered this material on the bottom of the shed …( please see attached pics) right around the outside …is it some  waterproofing material?? Should it be attached to the wall rather than sitting in the dirt??

[JacobZ]

Hi @ChrisA,

I am suggesting you attach the top of the corflute to the Hardiplank using Sika 11FC and have the bottom edge of the corflute extending below the slab. If the top edge is sealed well using the Sika 11FC, you will create a solid physical barrier that will direct any water down into the drainage that you will have installed below. I've done up a quick render to help demonstrate what I mean. Please note I have made the corflute yellow, so it is easier to see against the background.

         

What you've found is called dampcourse or plascourse, similar to this Consolidated Alloys 380mm x 30m x 500um Black Poly Dampcourse Plascourse. It is often used as a barrier between timber and concrete to help prevent timber rot as direct timber to concrete contact is not advisable. It is likely that it is attached to the underside of the timber bottom plate as a barrier between it and the concrete below.

If you have any other question, please keep me updated.

Jacob    

[ChrisA]

Hi Jacob , 

Thanks so much for all your help!!

Just wanted to clarify ...I could glue the corflute on the first level of hardiplank as seen in the above picture and it will extend down into the trench?

Also can you please explain what the different colours are in the diagram ... I can see the corflute but confused with the others.

Additionally  with the french drain using the slotted ag pipe do you think I need to put in some type of drainage fabric? 

Finally, do you think it would be ok to the top of the french drain just the drainage gravel given its about the sides of the garage near the fence.

[JacobZ]

Hi @ChrisA,

Not a problem, that's why I'm here.

Just wanted to clarify ...I could glue the corflute on the first level of hardiplank as seen in the above picture and it will extend down into the trench?

Yes, that's correct. You should glue the corflute onto the Hardiplank and have it extend down into the trench before installing your French drain. This will direct the water down into the drain preventing it from getting under the Hardiplank and timber bottom plate and into your music studio.

Also can you please explain what the different colours are in the diagram ... I can see the corflute but confused with the others.

In the diagram yellow is corflute, white is Hardiplank, the bluey grey is concrete, and the brown is the timber of the wall. 

Additionally  with the french drain using the slotted ag pipe do you think I need to put in some type of drainage fabric? 

Yes, French drains are usually wrapped with geotextile fabric such as GRUNT 1 x 10m Non Woven Geotextile Membrane, this is to stop soil getting in between the drainage gravel and preventing the flow of water.

Finally, do you think it would be ok to the top of the french drain just the drainage gravel given its about the sides of the garage near the fence.

Are you asking if it would be ok to just leave the area surface area above the French drain as drainage gravel? If so, then yes absolutely this would be fine, it would actually contribute a great deal to promoting good drainage.

I hope this helps to clarify your questions. My colleagues and I are always here if you have others moving forward during this project.

Jacob