# 40mm waste and joists

#### JayJay1978

I'm thinking of swaping the bath in our ensuite for a shower, the bath is a very slow drainer due to cowboy installation. I want the new shower to have a nice fall on the waste pipe, and I also want it under the floor.

1. My wife does not want any boxed in pipes
2. The basin will be inbetween the shower and outside wall
3. External stack
4. Floor joists are in way
5. No other route for pipe

So I can properly plan the shower I need to know if its possible to run a 40mm waste pipe through about four or five 8 " joists.

I know there's an exact calculation but I just wondered if the pro's get there calculator out or just go be their gut feeling in these sisuation. I plan on using my angle drill and bolting 4x2 lengths along each holed joist as I like to do thing overkill.

What do the pro's do in the real world in these situations?

If memory serves me right (I await derision ), the holes need to be at least 400 from the wall, half way down the joist and no more than 25% of the height of the joist. So an 8" joist is do-able. You need a slope of 18-80 mm per metre.

1. My wife does not want any boxed in pipes

What do the pro's do in the real world in these situations?
Get a different one?

Boxing in can be done neatly if you take your time. Rather that than hacking your joists about to such an extent.

I'm thinking
plan on using my angle drill and bolting 4x2 lengths along each holed joist What do the pro's do in the real world in these situations?
Use some WBP ply and glue it with gripfill to joist then bolt through - instead of the 4x2 More strength in shear

surely if it's going outside then the waste can be pushed through the holes from the outside?
you'd need to be a good shot with the holes though, or use oversized holes to allow for them being slightly out..

I'm with htgeng, notching/drilling joists for a waste run is a terrible idea; trade her in or tell her not to meddle in things she has no idea about!

#### DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Replies
7
Views
1K
Replies
1
Views
884
Replies
8
Views
8K
Replies
2
Views
2K
Replies
3
Views
1K