Rot in Bathroom Floor Joist

[parso123]

Hi, We are renovating the main bathroom and I have discovered rot in the floor joist. I am thinking after I remove all the rot, I will treat it with a rot preventative and build it up with builder's bog. Should I also install a sister joist alongside the joist? Thanks much, Dale

[Tools]

That looks like borer rather then rot to me. Is it dusty? Either way, just rip the joist out and replace it with some F17

Tools

[pawnhead]

Builders' bog won't help much unless you're planning on spending a lot of time under your floor admiring your joists.
It looks like less than 10% damaged, which I'd say isn't that bad as to warrant an extra joist, but you could always play it safe since the floor is up now anyway. Check from underneath, if the outer joist has any rot as well, and if so, then I would cleat another joist on, staggered nailing at about 150mm centres.

The main thing is to fix the source of the problem. It looks like there's not a lot of ground clearance there, and there may be insufficient sub floor ventilation, but I suppose it's more likely a leak in your old membrane.

Edit:

That looks like borer rather then rot to me.

Come to think of it, it does look like that doesn't it. At least it looks solid where it's supported by the bearer, and it would be a pain to remove it so the most I'd do is to cleat. It doesn't look all that bad to me so long as it doesn't get any worse..

[Colin Howkins]

Parso,

I've been down this track. It doesn't look that bad to me. However, whichever way you go to repair it you have to treat the timber to prevent it coming back.

Used to use creosote, it works, but it's pretty wild stuff. Known carcenogenic, will burn exposed skin, and even exposure to fumes can have you looking sunburnt.

Nowadays I use copper napthante. Dont buy it from a paint shop, you will need a wheelbarrow full of cash. Do a lap of the chemical companies in your neck of the woods and you will find you will be able to buy a 20 litre container for about $20.

There is a mob called Vital Chemicals here in Brisbane Ph 07 3288 3500. If you can't get it in your neck of the woods maybe Vital could ship it down to you.

I spray it on with a garden sprayer. Works well, and no where near as dangerous as the old creosote.

Colin Howkins
Graceville Qld

[parso123]

Thanks for your replies. I'm sure now that it is borer and not rot... there is very little clearance under that part of the house, so we're not sure how to go about increasing sub floor ventilation, but we'll see what we can do.

[blondie]

Hi, Peoples, Is it Sap Wood that is breaking down?. If so, not a problem as far as I know, as it can be a small part of the timber that can be used and a certain borer can attack it but not the hard wood. I could be totally wrong, but an idea?