How to stop water coming in from under tilt garage door?

[unawarek]

During the storm yesterday (in Brisbane), I realised that water was coming into the garage from under one of the tilt doors. The water level just about covered the top of my feet, and is the first time it has ever happened (there have been a few occasions that a little bit of water has seeped in from under the door, but not to this extent).

This probably happened to the previous owners, and they seemed to have made a little "hump" of concrete just behind the garage door to slightly raise the floor. This has worked well in the past and stopped the majority of water from coming in. I tried using a garage threshold seal but because of the "hump", the floor isnt completely flat and I cant stick it down properly.

Is there anything I can do to either slightly raise the level of the floor within the garage, or perhaps make the floor slightly more level so i can silicone down the threshold seal? Can I maybe silicone/glue a D-shaped rubber seal along the threshold (not sure how it would hold up to a car driving over it everyday), or use some foam to pad it out?

Because of how the driveway is, I don't think I can attach a seal on the bottom of the door itself - there just isnt enough clearance (if you look at the first photo, the door just about clears the lighter grey part of the driveway to open).

Here are some photos:

Front of the door with part of the driveway jutting out (just below the maroon piece of timber), if you look carefully you can see where the paint from the door has scraped off when brushing past the floor

Inside of the door

Inside of the door with the concrete "hump" just behind where the door closes (next to the brickwork)

Another view of inside of the door with the concrete "hump" just behind where the door closes

[Ari]

@unawarek unfortunately I have zero advice but am keen to follow your post as I'm expecting a similar issue with my garage the next time a big rain event/flood occurs in Brisbane. 

My current strategy is to not worry about the garage, just ensure things are raised off the floor, and focus on the house doors instead.

Thanks for asking the question - I am sure any advice will be used by many community members.

[Jason]

Hi @unawarek,

Could you please share some wider images of the whole area leading up to the garage door? It will help members to get a better idea of what you are working with and provide more specific and helpful advice. 

It sounds like a very similar situation to what what faced by member @Bluetooth in this discussion - How can I protect my garage cabinets from floodwater? Have a look at the discussion and see if you might be able to add a drainage channel before your garage door.

Thanks,

Jason

[unawarek]

@Ari 

Almost everything in the garage is already elevated, and I'm not too concerned about the items in it. The door into the house is about 4 to 5cm higher than the garage floor, and the water level didn't come anywhere close to it too. I'm more worried about the back wall of the garage though - its a gyprock wall with a timber skirting at the bottom. I think the water just about touched the skirting this time around. 

@Jason 

Here are some wider images. I know that installing a drain might be the best way around it, but I was hoping for a fix that would be a little less costly 🤣.

[Ari]

@unawarek  Ah got it.  In that case my best suggestion would be to put 30 cm of flood proof building board over your gyprock and seal that.   Brisbane City Council replaced the gyprock in loads of flooded properties in Milton and Rosalie (and presumably other suburbs) with this up to waist height, and in the Feb 2022 floods people just hosed out instead of having to replace.  I'm not sure where you could buy it though.

Probably more effort than you want but less than installing a drain.

The PDFs on this page of the QRA site might give you other ideas https://www.qra.qld.gov.au/resilient-homes/flood-resilient-building-guidance-queensland-homes

[EricL]

Hello @unawarek

It's great that you've received excellent advice from @Ari. I suggest changing the angle of the hump with Bastion 20kg Concrete Mix. The former owners had the right idea in mind. However, they did not anticipate the increase in rainfall and the result of their handiwork. Instead of helping the water flow towards the drain, they've actually hindered it by putting a hump right next to the lowest point of the driveway.

The water which would have naturally flowed towards the drain is now being slightly diverted back to the centre of the driveway. Once there is enough water it will start flowing over the hump and into the garage. I propose adding more cement at the other end of the entryway and angling it towards the drain. The water with its momentum will flow onto the hump and be diverted towards the drain and your open garden instead of the garage.

I've placed a sample sketch below to give you an idea of how to form the new angled hump. Please remember to rough up the surface of the hump and driveway before you apply the new concrete. 

If you need further assistance, please let us know.

Eric

[unawarek]

Thanks for the suggestion Eric. Just a couple of questions:

1) What would I use to roughen up the hump and driveway? 

2) Do I just free-hand the angle of the new hump, or should I make some form of formwork? Also, what can i use to ensure that the new hump angles towards the drain?

3) Would I need to add anything to the new concrete hump to reinforce it?

Thanks!

[EricL]

Hi @unawarek

I suggest using a Trojan 4x15 Row Stainless Steel Wire Brush to rough up the surface of the old hump and part of the driveway. I propose using a builder's line to create a guide for the new hump. There is no need to make formwork for the new hump, however, if you feel that it would be easier for you to make with formwork then I suggest building one. 

The best way to get maximum strength from the concrete is to retard its drying time. Cover the freshly laid concrete with builder's plastic and spray it with water when the temperature gets too hot. It will take a while to dry off the concrete, but it will be very strong once it cures properly.   

Please make sure to wash the area you roughed up with your garden hose to make sure that it is clean and free of debris before starting.

If you need further assistance, please let us know.

Eric