Plasterboard&OSB Return

[MortarThePoint]

I'm looking to include OSB in the Bathroom wall but it's complicated by there being a return. The wall sheathing will effectively be changing thickness at the return which is a small challenge. Also, I may only be able to get 11mm OSB (or 18mm but same problem) which means it's not the same as the 15mm plasterboard. Below is a drawing of what I'm looking at. The green is 15mm or 12.5mm moisture resistant plasterboard, yellow is 11mm  OSB3 and grey is 15mm Duraline. All on 70mm C-Studs (BG) in blue.

 

[MortarThePoint]

The sketch above has the issue of the plasterboard needing to come away from the OCB towards the corner.

 

Or am I better off creating a small pocket in the corner to get filled by plaster when the wet plastering is done?

 

They may not look it, but the sketches are pretty much to scale.

 

[MortarThePoint]

I could put 36mm x 4mm stripwood behind the OSB3 at all its studs to make it effectively 15mm:

 

Edited May 3, 2022 by MortarThePoint

[HughF]

16 minutes ago, MortarThePoint said:

I could put 36mm x 4mm stripwood behind the OSB3 at all its studs to make it effectively 15mm:

 

I'd do this, just pack it out along that C stud

[Mr Punter]

Could you just have the plasterboard stop at the junction?

 

[MortarThePoint]

7 minutes ago, Mr Punter said:

Could you just have the plasterboard stop at the junction?

 

 

I was worried that it would affect the strength of the junction with the plasterboard stopping in free space rather than on a stud.

[Conor]

Move the two bedroom wall studs and then bring the dressing room wall stud between the two, so you have three studs at the one point. You could probably ditch the extra bedroom wall stud.

[MortarThePoint]

On 03/05/2022 at 16:07, Conor said:

Move the two bedroom wall studs and then bring the dressing room wall stud between the two, so you have three studs at the one point. You could probably ditch the extra bedroom wall stud.

 

That doesn't work so well with the 1200mm gauge unfortunately

[MortarThePoint]

I've gone with the stripwood approach. Hard to see, but I left a 3mm gap between the two boards by resting the top one on screws sat on the bottom one whilst installing. Also 3mm gap at the blockwork and will do he same at when I add the 15mm plasterboard continuation.

 

I've not taken the OSB to the ceiling as that is 2.7m and there won't be cause for anything up there (will there?). I'll pack the studs at the top with stripwood and strips of OSB just at the studs.

 

I raised the OSB about 10mm off the floor, you can see a strip of OSB under the sheet edge which I will then chop up and use as above.

 

Stud positioning to avoid pipe penetrations is the next key thing. The sink waste is going into the wall 600mm room the RHS end of the OSB (400mm stud centres). It will then pop out in the bottom left corner and I expect I will need to pass water feeds in there too to then take to the sink and continue round, into the return and over the door in the return to the shower. The other route to the shower is along with the shower's waste, but I'd need to cut a trench into the screed for it to continue past the shower trap and onwards to the stud wall.

 

[Note: the stud in the odd position is just moved temporarily

 

Edited May 7, 2022 by MortarThePoint

[MortarThePoint]

I wonder if I should have held the OSB a little higher than 10mm off the screed, but the plasterboard will need to come down about 5mm above the screed I presume.

Edited May 7, 2022 by MortarThePoint

[MortarThePoint]

Here's what the return will look like in terms of OSB:

[MortarThePoint]

On 03/05/2022 at 16:07, Conor said:

Move the two bedroom wall studs and then bring the dressing room wall stud between the two, so you have three studs at the one point. You could probably ditch the extra bedroom wall stud.

 

I'm intrigued by your mixture of water pipe sizes. You appear to have thinner and thicker water pipes. I am currently planning my plumbing so it would be good to understand.

[Conor]

1 hour ago, MortarThePoint said:

 

I'm intrigued by your mixture of water pipe sizes. You appear to have thinner and thicker water pipes. I am currently planning my plumbing so it would be good to understand.

22mm for the heating manifold.

15mm to showers

10mm to sinks and toilets.

Supposedly faster heat up time. Works well in our main bathroom. We've only 2.5bar of mains pressure so flow rates are quite low

Probably wouldn't bother again as using 10mm stuff is more expensive, you have to adapt up to 15mm or whatever at each end so more fittings needed.

 

 

[MortarThePoint]

12 hours ago, Conor said:

22mm for the heating manifold.

15mm to showers

10mm to sinks and toilets.

Supposedly faster heat up time. Works well in our main bathroom. We've only 2.5bar of mains pressure so flow rates are quite low

Probably wouldn't bother again as using 10mm stuff is more expensive, you have to adapt up to 15mm or whatever at each end so more fittings needed.

 

Sounds good. When I did the UFH pressure test we had 5.5bar so will hopefully be good for water pressure. I guess we'll use 15mm allround then for water feed (not UFH), thanks for sharing the insight. Looks like you had some good service gaps in your concrete floors, but I can see some pipes coming through the concrete into the floor channel of the wall. What size holes did you use in the concrete? Did you bother sleeving the pipes as they passed through, or just filled with foam? Similarly, what did you do when passing through blockwork walls?

[Conor]

8 hours ago, MortarThePoint said:

 

Sounds good. When I did the UFH pressure test we had 5.5bar so will hopefully be good for water pressure. I guess we'll use 15mm allround then for water feed (not UFH), thanks for sharing the insight. Looks like you had some good service gaps in your concrete floors, but I can see some pipes coming through the concrete into the floor channel of the wall. What size holes did you use in the concrete? Did you bother sleeving the pipes as they passed through, or just filled with foam? Similarly, what did you do when passing through blockwork walls?

At that particular point we left a gap in the hollwocore slabs - about 150mm. Same at the other side of the house at the other bathroom.  Didn't fill in around the pipes, just used a combo of pipe lagging and conduit. I concreted in the hole up to the edge of the stud and floored over. For holes in the concrete walls, I drilled 25mm holes and sleeved the pipe through with conduit. For bigger services, I use a 100mm core bit.

[Nickfromwales]

9 hours ago, MortarThePoint said:

we had 5.5bar so will hopefully be good for water pressure. I guess we'll use 15mm allround then for water feed

Do the hot feeds to the wash hand basins in 10mm. I do this on every job where running an HRC to an outlet is on the borderline of being overkill. Plenty of flow rate even with mains which are half of what you have there. Its just one more fitting each end, so an extra £10 per 'leg'. Chicken feed when you pay nearly £3 for a cup of coffee........

[MortarThePoint]

3 hours ago, Nickfromwales said:

Do the hot feeds to the wash hand basins in 10mm. I do this on every job where running an HRC to an outlet is on the borderline of being overkill. Plenty of flow rate even with mains which are half of what you have there. Its just one more fitting each end, so an extra £10 per 'leg'. Chicken feed when you pay nearly £3 for a cup of coffee........

 

Good point, skinny pipes to basins for faster hot water (0.35l/m vs 1.00l/m, but more constricted). I presume HRC is a looped system that makes for instant hot water which isn't what we'll have. As this basin is about 6m from the cylinder I'll probably have a dedicated pipe for it as then it can be 10mm all the way, unless you'd be happy with 10mm for a bath feed?

Edited May 12, 2022 by MortarThePoint

[Nickfromwales]

5 hours ago, MortarThePoint said:

 

Good point, skinny pipes to basins for faster hot water (0.35l/m vs 1.00l/m, but more constricted). I presume HRC is a looped system that makes for instant hot water which isn't what we'll have. As this basin is about 6m from the cylinder I'll probably have a dedicated pipe for it as then it can be 10mm all the way, unless you'd be happy with 10mm for a bath feed?

You cannot do 10mm from the bath feed or you miss the whole point of the 10mm pipe   

Indeed, do the run to the basins ( hots ) in 10mm ( all of them ) plus the kitchen sink hot too. If you’re worried about flow, hook up a length and test run the kitchen tap before committing. I’d be shocked if you weren’t happy with the 10mm feeds, on the proviso that they all tee off minimum 15mm supply pipe. 
Done enough of these to speak from experience on live installs, so this is not a fag packet recommendation. 

[MortarThePoint]

1 hour ago, Nickfromwales said:

You cannot do 10mm from the bath feed or you miss the whole point of the 10mm pipe   

 

I think I understand. I was thinking it is to reduce dead volume before hot comes through, but is it to create a more restrictive path than that to the bath so the bath doesn't suffer a loss of pressure?

[MortarThePoint]

@Nickfromwales or @Conor : sorry for the basic question, but do you do a 15mm feed all the way back to the mains supply or do you do 22mm to the room and then 15mm / 10mm to the various places in the room?

[Conor]

13 hours ago, MortarThePoint said:

@Nickfromwales or @Conor : sorry for the basic question, but do you do a 15mm feed all the way back to the mains supply or do you do 22mm to the room and then 15mm / 10mm to the various places in the room?

You have a manifold at your main supply point at your hot water cylinder. You run the individual pipe all the way from the appliance to the manifold as a single run. So for a standard bathroom you'd have three 10mm pipes (WC cold, sink cold, sink hot), two 15mm (shower cold, shower hot).

 

It's a lot of pipe compared to doing it the old way, but it's fast and no more expensive as pipes are cheaper than fittings. 

[Tom]

Can I ask what the rationale is for having the cold in 10mm too?

Why not 10mm for the shower?

[Conor]

You won't get the flow rate with 10mm for a shower, bath or kitchen sink.

 

10mm pipe is easier to work with but there isn't really a cost saving so just do 15mm for everything except the hot sink outlets.

 

I did all my WC s in 10mm as I had a 10mm manifold separate from the rest so can be run on recycled or rain water.