How to fix water ingress by adding drainage?

Smouch

Hi all!

I have recently purchased a property and its a bit of a strange layout with two enclosed garages on either side of the house with front and rear roller doors.

The yard slopes toward the house and we have been having water ingress into both garages during heavy rain. I have a few questions about the way forward:

1. The garage door threshold ends too soon and does seem to allow water ingress. Note where the track is in the below picture and where the seal mark is on the floor. Should I extend the threshold inwards so the door rests on it? Would that just be a case of getting some more concrete?

2. The channel grates seem to be pretty shallow for the amount of water that is hitting it, I haven't noticed it overflowing as yet but one morning (when we had significant ingress around 1 inch of water throughout both garages) the grates had lifted up and were found around the side of the house. Should I look to deepen the channel? Additionally, there doesnt seem to be a slope toward the drain, is this required/recommended? 

3. The water seems to run down the centre of the pavers around the side of the house. Should there be anything (weather seal of some kind?) between the house brick wall and the pavers? I can't tell if im getting ingress through the bricks on the side. Should I be installing a bed of gravel and some agi line of some sort?

4. There is some significant erosion aound the water heater as seen below. Would my best bet to be remove the pavers and build it back up with something, then pavers back on? What would be the best way to replace the material sitting under the concrete that has eroded?

5. The rest of the yard is set out as below. We get very spongey grass as my neighbour informs me there is clay only 300mm down. Where would I be best placed to run some Agi line? I was thinking of running a channel grate along the red line to assist with offsetting the amount of water the garage grates are required to deal with.

Apologies for the long post! Any and all inputs are greatly appreciated, cheers!

MitchellMc

Welcome to the Bunnings Workshop community @Smouch. It's wonderful to have you join us, and many thanks for your question about home drainage.

Water ingress like this can become a real issue over time, so it’s good you’re being proactive. Starting with the garage threshold, it definitely sounds like the current setup isn’t allowing the door seal to do its job properly. Extending the threshold with a small concrete strip or ramp so the door closes against it would help stop water from entering. You could do this yourself with a small batch of rapid-set concrete, just ensure there’s a smooth transition and that it doesn’t interfere with the roller mechanism. 

In terms of the channel grates, if they’re popping out during heavy rainfall, that’s a sign they’re being overwhelmed. It might be worth upgrading to deeper channel drains or at the very least, ensuring there’s a proper fall toward the outlet. Water pooling or running slowly suggests there's little to no slope, and ideally you'd want at least a slight gradient to keep things flowing. Also check that the outlet itself isn’t blocked or undersized for the volume of water.

Regarding the water running along the side of the house, it’s not uncommon for gaps to appear between pavers and brickwork, and water can find its way through. While a flexible caulking could help reduce water entering at the edge, it’s more important to divert the bulk of the water away from that area. Installing an ag line beneath a gravel trench can help with this, especially if it’s placed along the base of the wall where water tends to track.

The erosion under the hot water system is also a worry—it looks like water has undermined the base. Removing the pavers and backfilling with compactable road base or gravel before relaying the pavers would help restore the area. You’ll also want to ensure there’s no pooling water running under the slab. If the concrete has been undermined, you may need to pour additional concrete to support the edge.

Finally, with the rest of the yard being spongy and underlain with clay, installing an ag line in that area makes a lot of sense. Running it along the red line you’ve marked should help intercept runoff before it reaches the garage. Combining that with a new surface drain could ease pressure on your current channel grates and reduce water buildup around the house. Just make sure there’s somewhere for the ag line to discharge—whether that’s a stormwater pit, soakaway, or suitable drain point.

Please let me know if you have any questions.

Mitchell