Garage damp

[DCJA]

We moved into a new build house in November 2019 and the garage walls are of course single brick. During the bad weather the moisture seeped through the upper bricks and it led to the pooling of small puddles along one of the inner sides. It was fairly clear that this was seeping into the garage from above the dpc.

Since then I have applied a brick sealant to the outer brick face (Thompson’s). In the longer term would it be of value to “tank” the lower metre of the inner wall or would this increase capillarity and cause other issues?

[New Home Expert]

You have done the only thing you could do and hopefully it will solve the issue.
You may need to use tow coats and the new Thomsons Water seal in my opinion isn't as good as the solvent based original.

There is nothing to be gained from tanking the inside as any water that gets in from outside would just blow the tanking off.

In my garage, I also lined the inside with polythene then added battens and attached flooring grade chipboard to line the inside keeping moisture behind and have had a dry internal wall for 20 years and have a wooden wall for easy fixing!

Given you have ponding on the floor, I would check if there is not a leak to the roof or any flashings.
You may also have partially filled mortar joints enabling the water to penetrate more easily.