Seal concrete before building deck over the top?

[dmcleod]

We’re planning to build a low level deck over our exposed aggregate courtyard using aluminium framing and Ecodeck slats and wanted to know whether we should clean and re-seal the concrete before we build the deck over the top?

I know sealing it will only last for a few years, but thought it might be worth doing to help delay any deterioration in the concrete due to moisture/moss etc. We were planning to re-seal the parts of the concrete that won’t be covered by the deck anyway, but didn't want to do the concrete where the deck will sit if it wasn't necessary.

Some more context:

• I don’t believe the concrete has been re-sealed since it was originally poured 12+ years ago
• The courtyard has reasonable drainage (see photo below)
• To the left of the rainwater tank man hole is fairly flat
• To the right it slopes away to the garden bed/drain.
• The courtyard isn’t covered

If the consensus is to go ahead with re-sealing, would a penetrative sealer be the best option and should we acid etch the concrete before applying the sealer?

[MitchellMc]

Welcome to the Bunnings Workshop community @dmcleod. It's fabulous to have you join us, and many thanks for your question about sealing concrete.

If the minimum quantity of sealer you need to buy is enough to seal under the deck, then I'd say go for it. It could prevent moss from growing, but I don't think the concrete will degrade much once it's covered by a deck. If you didn't have good drainage, then I would advise you not to seal it as the sealer will prevent water from being absorbed by the concrete and could cause pools to develop and sit there.

Most penetrative sealers don't require an acid etch on aged concrete unless there is grease or heavy contaminants present. Depending on the product you choose, I recommend following the instructions. The Crommelin concrete and paving sealer is a great choice.

Please let me know if you have any questions.

Mitchell
 

[dmcleod]

Thanks for the reply @MitchellMc! I'll take another look at the flat(ish) part of the courtyard because there is a concern that water may pool on that side.

[Jason]

Let us know if you need further assistance @dmcleod, we're here to help. 

We are also looking forward to seeing the project take shape. Our community members love a good decking project so please share regular updates as you make progress.

Jason