Advice drilling 32mm holes in 80mm joists

[Chubber]

A simple hardwood gauge/ template ( like a bench hook with one ledge ) drilled 3mm at the appropriate distance would save a lot of faffing about with a square and pencil. Used to spot-drill the hole position it would increase the likelihood of the distance from the edge of the beams being equal.

Oh, if it's for cold water, add foam pipe insulation as you go even if indoors to avoid condensation of moist domestic air after each time a fresh draw of water* .

(* Ask me how I know...)

 

[robgul]

I wouldn't contemplate a flat bit as the kick-back risk is high, especially when in a confined space between the joists - an auger bit is the best option as it threads itself and self-clears - just run it slowly and steadily.

 

[glenfield2]

Thanks for everyone’s comments really appreciated.
My plan is to thread the pipe through the stair opening
The pipes will be 22mm copper, I don’t use plastic anymore after a pipe leak after a mouse eat through a pipe. I also have an M Press tool to crimp the pipes makes a great job
I guess I could make the holes smaller if I make a jig I was just concerned if the holes were not bang on or totally straight with threading copper through would make them tight.
I have seen an erbauer 90chuck attachment on Screwfix I was going to give that a try.
I fancied the 90 degree chuck for my fein drill but it’s £100

I’ve been through a couple of those screwfix 90o chuck attachments and IMHO they are pretty ropey and clumsy to use. Very awkward to hold everything especially if reaching between joists. Both also had the little magnetic bit holder fall out so the drills keep dropping out. Fun.
I’d buy the cheapest 90o drill. Even s/hand. You can always sell it again.

 

[Jake]

At post Nº3 you stated that the maximum hole size was 25% of the Joist depth. 25% of 250mm is 62.5mm not 31.25mm

I was giving depth for a notch on the underside not a hole (notch is 12.5% not 25% because it weakens the stressed edges of the joist not the more neutral part in the middle).

 

[johnnyb]

100 holes in 400 centres? I'd ponder a better solution up

 

[Herr Nilsson]

Similar to a mason’s line, stretch a piece of string between the furthest points of the pipe run a few mm below the joists! This is your datum for measuring the height of each hole. A jig that references off each joist may not be the way to go if there isn’t a uniform distance between the bottom of your joist and your string line.

*Edited: Oops, just read that ChaiLatte suggested this already at the start of this thread. *

 

[Jake]

I'd start the holes at the stairwell where you are feeding the pipe from and feed pipe as you go - still need to mark to make sure you don't drift, but a chalk line the length of the run and some sort of depth gauge to give you a height mark on each joist, then push the pipe through, check it's in line with the marks, draw around the end, retract, drill, repeat.

Or, like Johnny says, maybe find another way around.

 

[dizjasta]

As Jake has pointed out. If a hole is drilled through the center of depth of the timber joists and this hole diameter is limited to 25% of the beam depth then the reduction of joist bending strength is limited to 2.5%.

 

[joncooper27]

Thanks for everyone’s suggestions I was thinking of a Beaver type drill the string line idea is good and threading through as you go sounds good!
If anyone can think of a better solution as it’s not something I’m looking forward to doing over Christmas holidays be gratefully appreciated.
I have been reading the regs for drilling holes in beams I did not realise they were detailed so much! Glad I did as the new building inspector I have is quite fussy compared to my last one!

 

[owen]

Using a laser level is a good way to get a nice straight line for drilling the holes

 

[Beau]

I recently had to thread some 15mm plastic pipe through 50mm joists at 400 centres. Screwfix had their Erbauer version of the Beaver bit available that day so thats what I got. It did the job and being able to put it in the impact driver was a bonus as thats the shortest drill/driver I own

 

[RobinBHM]

22mm copper is pretty stiff.

If you are using a 32mm drill bit that’s not much tolerancece you need the holes bang on.

You need to check to see if the joists are all straight and in line with each other, if they are over 5mm out the holes won’t line up.

Is there a reason why you can’t notch out? - that’s what a plumber would do. Maybe the buildings regs won’t allow it

 

[Howie65]

Hi,

I know that one answer mentioned fitting battens to the underside ?
This is the route I would recommend but using 2 x 2 (50mm x 50mm) timber which is actually 47mm if you were to use kiln dried CLS timber to minimise any deviation/bumps/hollows - but you will no doubt still need to pack in places as joists are very seldom all in a perfect line.
You could fit at 600centres especially if using 15mm board and you would need/recommend fitting noggins to both perimeter and joint line to eliminate chance of cracking later(1200/1220 centres to suit board).
You can come in a maximum of 75mm from perimeter to limit overhang of board to maximum of 75mm(building regs) which you could run the pipe in if needed as long as any trades are aware of perimeter pipe !!
But you could pretty much run the pipe anywhere you wanted to suit - shortest route ideally.
As long as you can maintain 2100mm including plasterboard thickness of headroom in the stairwell area off the outer point of tread/riser (top of stair string would be a sure place to give you a bit extra to play with)
For the cost of the extra timber it would be a lot easier as long as you can accommodate the loss of 60ish mm height loss ?

 

[TimV]

22mm copper is pretty stiff.

If you are using a 32mm drill bit that’s not much tolerancece you need the holes bang on.

You need to check to see if the joists are all straight and in line with each other, if they are over 5mm out the holes won’t line up.

Is there a reason why you can’t notch out? - that’s what a plumber would do. Maybe the buildings regs won’t allow it

Agree, and bear in mind that the joists may flex, so even if the run of holes is straight when you put the pipe through, it may pinch if someone walks above, or the building moves (which they do) etc. So - for rigid pipe, do allow for that in the clearance, whatever you end up doing.

 

[Bingy man]

A 32mm hole is excessive for this size pipe. 25mm, accurately located, is more than adequate.

Spend the time and mental effort getting the holes in the right place, not the physical brute force on punching a large hole though many joists.

Work out the cross-sectional area of 25mm dia. and the same for 32mm dia. That is the extra-over percentage of material you need to remove. Why do an unnecessary job for a 64% cut in wages?

Completely agree 25mm is plenty and still allows a little wiggle room . You should never remove any more material than is necessary on a structural joist . I’ve done this in the past to replace a gas supply. Cut out a brick or two from outside, mark the first few joists , feed the pipe in ( easy with a 2nd pair of hands ) as the pipe butts up to the next joist use the end of the pipe to mark the next hole , impact driver and a stubby drill bit will do it , as above longer bit for any double joists . Easy and no need for jigs or expensive adapters that you might never use again ..then simply continue until you have your pipe where you want it ..

 

[JSW]

I was thinking of a Beaver type drill the string line idea is good and threading through as you go sounds good!

If you're threading through as you go, be aware the joists may be canted/cupped/not plumb, so if using a beaver type bit, you'll have to correct the angle as you go, IE- if the joist is canted, the bit will engage the joist at an angle, the natural reaction would be to realign to the face of the joist, which will skew the angle of the hole. By the same token, you won't be able to use a pre-drilled timber block as a guide.

 

[Bingy man]

The one thing not mentioned by the op is what the pipe is for - gas water etc . Sparkles often run cables through the centre of the joists and drilling another set of holes could seriously weaken the joists especially in a high traffic area. I know the regs for gas pipes next to cables is 25 mm and 150 from junction boxes etc . I’m sure water pipes will also have regs to adhere to ..

 

[RobinBHM]

If you want a dead straight line, just use a chalk line to get one axis, then screw a piece of wood to the underside of the joists and pack it out so its dead straight -then use that as a datum and measure each hole off that

I not sure where the pipe needs to be in relation to the joists, but if it was me I would position it within 300mm of the end of a joist -if you have to do a long return down parallel to the joists to get back to where you want to exit, thats no deal, its in between the joists. If you are close to the end of a joist notching out doesnt weaken the joist

I used 22mm copper pipe to connect hot and cold direct feeds to a new shower and I had to go middle of joist -it took a fair bit of working out, 22mm is not flexible at all, so I had to put in a few joints -all straight forward with soldered joints