waterproofing old deck joists

**havabeer69** · 18th January 2024, 09:54 PM

hi

wasn't sure if this should be in the waterproofing or deck section. Basically I'm replacing an old timber deck with a new steal subframe one. the old bearer has been removed leaving the joists that run into the house framing still there. My new deck subframe will sit over these old joists. I'm going to trim them off flush with the exisiting brickwork.

how ever I'd like to seal them up just so bugs, water etc can't get in. My main plan of attack is to trim them off flush, seal up the larger gaps with an exterior paintable silicone and coat with a waterproof membrame... but which one to go with?

I have a very big tub of left over "water based bitumen paint" and a unused small tub or "exterior grade waterproofer"

the painted area will have a new ledger beam/bearer covering it so will see little to no UV. I really want to lean towards the black bitumen purely so any visible area's don't stand out as much as the "blue" waterproofer. I just can't remember which one handles UV and exposed area's more

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**rwbuild** · 18th January 2024, 10:02 PM

Just a moment...

**mic-d** · 19th January 2024, 08:15 AM

^^ this.

Also I would be tempted to have an apron flashing made up to give protection to the old work below and the ground level area. You'd chase out the pointing above the ledger and seal it into there. The flashing would look like a 'Z' only 90º angles with a short 10mm as the top of the Z that goes into the brickwork and a longer bottom to the Z that suits the application. Alternatively you can do it as a composite flashing where the top and bottom of the 'Z' are supplied as two overlapping parts which work the same as the one-piece flashing once installed and riveted together, but it allows for more tolerance for run out etc.

**havabeer69** · 19th January 2024, 08:59 PM

Originally Posted by mic-d

^^ this.

Also I would be tempted to have an apron flashing made up to give protection to the old work below and the ground level area. You'd chase out the pointing above the ledger and seal it into there. The flashing would look like a 'Z' only 90º angles with a short 10mm as the top of the Z that goes into the brickwork and a longer bottom to the Z that suits the application. Alternatively you can do it as a composite flashing where the top and bottom of the 'Z' are supplied as two overlapping parts which work the same as the one-piece flashing once installed and riveted together, but it allows for more tolerance for run out etc.

that area is actually under cover and the deck will be sloped away from the house so it will receive little to no rain exposure other then a maybe a pressure wash so the flashing/apron is possibly a bit of overkill.

I really should have just googled the products... turns out I could probably rule out the bitumen one

Note: Not suitable to be tiled over, use Crommelin Shower Waterproofing Membrane in this situation. Not suitable for use if UV stability is required, use Crommelin High UV Resistant Roof & Wall Membrane in these situations.

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