How to fix waterproofing around outside wall?

jack7676

Hi all,
would love some advice and recommendations.
I’ve recently purchased a weatherboard house and one of the room constantly have this damp smell when we don’t air the room, I think it is because water is coming in from the outside.
outside of the house, as you can see from the picture, the original owner had brick paving right up against the base board. As you can see in the photos, the board has already started to rot as it is mostly under the brick and sand. Because of how the backyard is laid out, I cannot lower the brick pavers without significant work.

I’m keen to get advice on how to fix this. I was thinking of replacing the base board with fibre cement, but cannot find anything similar in style, so was thinking of keeping the base board, spray some wood hardener, tape the plastic over the slab with the timber with g tape then paint over with several layers of bitumen rubber.
I was also thinking of putting some French drains along the edge of the house to drain out any excess water. Only issue is I’ll struggle with fall and might just be level.
thoughts? Any recommendations?

thanks

Jack

JacobZ

Hi @jack7676,

Welcome to the Bunnings Workshop community, it is fantastic to have you with us.

Unfortunately, you will always have issues if the ground level is higher than the slab, which it appears to be in this case. When soil, sand, or paving sits above or tight against the slab edge, moisture in the soil will sit against the slab edge, where it can transfer into the slab and any timber that it touches. Ideally, you need to reduce the height of the soil or paving so it sits below the top of the slab. Even if you cannot regrade the whole yard, you really do need to lower it at least along that wall to create proper clearance.

Without lowering the ground level at the wall, any sealing or coating solution is only a temporary fix. Moisture management and correct clearances are what will stop the damp long term.

If the timber is in the early stages of rot, it might be salvageable using wood hardener, however considering the circumstances, I would say the rot is going to be widespread and unlikely to be an effective solution. Replacement is likely the best option. There are fibre cement options such as James Hardie 4200 x 180 x 16mm Linea Weatherboard which would be a better option close to the ground, but you would still need to look at methods for keeping the water away from them as water will still soak into them and could be transferred into the timber weatherboards that are higher up.

A French drain can definitely help with groundwater or subsurface moisture building up along that wall, but it will not be effective if you can't maintain a fall along the length of the wall to a drainage point, preferably a stormwater pipe. You only need a fall of 1cm over 1m for agi pipe to be effective, which realistically should be manageable if you are already removing soil to build a french drain. If you are connecting into a stormwater pipe, then you would need the assistance of a plumber as this is consider plumbing work that requires a licence.

So, to summarise, the solution in my eyes is to reduce the height of the soil against the slab edge, replace the rotten weatherboard and install a french drain with slope to a drainage point, preferably a stormwater pipe.

Unfortunately, other solutions such as bitumen membranes and builder's plastic are unlikely to be effective long term if the soil is above the top of the slab.

Allow me to tag @Nailbag, @TedBear and @R4addZ to see what they think.

Jacob