Coring through load bearing wall?

[LA3222]

The wall running along my kitchen is load bearing and takes the weight of a wall directly above. The wall above carries three point loads, the ridge beam and purlins supporting the roof and transmits this load down through to the foundations.

 

Ground & 1st floor it is 89mm C16 construction. Ground floor has 9mm OSB racking. The studs for the ground floor are 2.5m high. To fill the void between the top of the studs and the underside of the first floor deck solid 89mm timber (glulam) has been used (approx 350mm deep). 

 

Now to my question. Can I put a 110mm dia hole through that solid timber to run a soil pipe through?

 

It would be right next to where the stud wall 'T's into the external wall. No door openings below it so the timber isn't acting like a beam there. No point loads from purlins directly over it. To my mind that timber is just a space filler for the most part except over the two doorways where I expect it acts as a structural beam so I'm leaning towards it not being an issue.  

 

Thoughts from my fellow self builders would be appreciated.

 

Attached are pics of the offending article from both sides.

 

 

[ProDave]

I would say yes.

 

In a similar situation in my own build, I don't have the solid glulam there, just isolated pieces of it directly under point loads like the supports to the ridge beam.

 

You are probably going to want to drill that a lot more for cables, pipes and MVHR ducts.

[PeterW]

Ask your engineer. That is a big hole to be drilling in a beam with no support. I would as a minimum be putting 6mm plates either side with a 120mm hole bored through them. 

[Nickfromwales]

If you removed a section 120mm wide, you’d have no issue whatsoever. It’s a load well distributed / managed over the whole width of the wall vs any specific point loading. 
If you can drill a circular hole at 120mm diameter then that would leave meat above and below and he more than acceptable. 
If it was a glulam this would be totally different. 

[SuperJohnG]

 

1 hour ago, Nickfromwales said:

If it was a glulam this would be totally different

 

2 hours ago, LA3222 said:

To fill the void between the top of the studs and the underside of the first floor deck solid 89mm timber (glulam) has been used (approx 350mm deep). 

 

Dunno if that's been missed? 

 

In my view. The glulam is there to support whats above. Where is the glulam supported?. You can see there is a direction change of the floor joists so.its a key interface. That glulam.is in bending doing all the work. You could not remove a section in between the floor joists as you remove the ability of the beam to support the UDL. 

 

I dont know much about Glulams, but if it was steel beam and JJI you can get a hole schedule for it. But dunno how that works with beams glued together. 

 

Disclaimer: I've been drinking so I feel I have read everything above but could have misread your post above

 

[LA3222]

9 hours ago, PeterW said:

That is a big hole to be drilling in a beam with no support.

The timber in question is fully supported by doubled up 89mm C16 timbers underneath it, so is it deemed to be unsupported?

 

7 hours ago, SuperJohnG said:

Where is the glulam supported?. That glulam.is in bending doing all the work. 

 

Disclaimer: I've been drinking so I feel I have read everything above but could have misread your post above

 

The glulam is supported across its whole length by two horizontal timbers stacked on top of the 89mm vertical wall studs (can be seen in the first picture).

 

To my mind it is not a 'beam', it is a packing piece/space filler - am I wrong in this thinking.

[PeterW]

I would check with the designer / engineer as they will know what is structural and what isn’t. You may find it’s part of a set of pieces that work as a structural component - better to know before you drill rather than after as you’re going to need to probably use a 125mm core bit which won’t leave much meat around it. 

[Nickfromwales]

8 hours ago, SuperJohnG said:

Dunno if that's been missed? 

Yup, cheers. 
 

A glulam is often used here as it’s more stable / quicker to install to get the full width cover at the top of the stud frame. Other options are 2x 44mm wide C24 solid timber joists which is a far less uniform end result ( and therefore non sympathetic to affixing pre-cut pozi joists to ) so that’s prob why it’s been chosen vs the requirement to take the kind of weight that it’s capable of taking. 
As @PeterW says, check twice drill once, as this is a new structure and you’ll need to preserve the frame supports warranties. 
The beam is not only supported by the double header of the stud frame, but also by the fact that the stud wall is racked with OSB for a huge uplift in structural integrity. 
Plating this between the pozi joists will do little to nothing, and I’m sure the SE will give you a green light to strategically penetrate that beam. I doubt they’d have any issue with you taking a 150mm section out completely, at one point midway, so you can then take cables through the gap there also. Smaller homes for MVHR and small bore plumbing can be made according to the SE’s advisories. 

[ProDave]

I agree with the others above that you should consult the engineer that designed it.  Several things seem odd to me about that construction.

 

The Glulam is not acting as a beam in the conventional way with a support at each end and a load in the middle.  It appears to be in compression (vertically) supporting the load above down onto the load bearing wall, and that bit of it to me suggests you could cut a dirty great hole in it without anything falling down.

 

I would want to know why it was done like that.  In a similar situation I usually (and in our own house) just see the joist ends extending onto the top of the wall, not being hung from a glulam like this.  It seems to make the construction more complicated.  I would want to know why.  As i said before you are going to want a lot more than just one soil pipe through there.

 

The other thing that strikes me as odd is the supporting wall is made of 89mm studs.  That seems very small.  I wonder if this glulam beam is what enables the load bearing wall to be so thin and that is it's main purpose?  Was there a reason for this wall to be made so thin?  (our two internal load bearing walls are 150mm)

[Nickfromwales]

1 minute ago, ProDave said:

Was there a reason for this wall to be made so thin?  (our two internal load bearing walls are 150mm)

Once racked with OSB, a 98mm stud wall, with double header and footer, becomes incredibly strong. I’ve only ever seen 150mm used on walls which are excessively high eg divider between two rooms that share the same vaulted ceiling each side. 
The glulam is used here for plug n play construction IMO as two bits of C24 would likely need to be packed and trained into position due to natural timbers instability. Glulam beams are inherently flat, straight and uniform, when pre-cut and sent as part of a TF kit. They’re usually oversized in length and trimmed during installation in this type of instance. 

[ProDave]

1 minute ago, Nickfromwales said:

Once racked with OSB, a 98mm stud wall, with double header and footer, becomes incredibly strong. I’ve only ever seen 150mm used on walls which are excessively high eg divider between two rooms that share the same vaulted ceiling each side. 
The glulam is used here for plug n play construction IMO as two bits of C24 would likely need to be packed and trained into position due to natural timbers instability. Glulam beams are inherently flat, straight and uniform, when pre-cut and sent as part of a TF kit. They’re usually oversized in length and trimmed during installation in this type of instance. 

But my point is why do it this way?

 

In our house, and many others I have worked on,  the posi joists span onto the top of the wall.  Whatever is above sits on the top of the posis joists.  Only in a few select places is a short length of glulam inserted to fill the space between joists, for instance where the cripple studs supporting the ridge beam land.

 

The construction in the OP is elegand and simple but makes it a bugger for services so somebody at the design stage must have thought about that and have an answer.

 

Ours probably has 150mm studs due to the height of the upper section all the way up to the ridge beam.

[Mr Punter]

Yes, you can drill your hole.  To play safe, install a couple of vertical 38 x 89 studs in the wall under and ask the TF engineer to confirm this is acceptable.  Be careful when you drill as the drill can jam without warning.

 

Incidentally, with the two horizontal 89mm timbers, one is the top part of the timber framed panel and the other is a top plate to join all the panels together.  They are not really regarded as structural beams.

 

It is this large build up of horizontal timber that causes shrinkage in timber framed buildings, but it is the standard way of doing things.

[Nickfromwales]

7 hours ago, ProDave said:

But my point is why do it this way?

Because the pozi joists don’t ( can’t ) take the load   They stop and start at the beam on purpose as they have no compressive / load bearing qualities at the tail ends. The above loads need to be transferred directly to the load bearing stud wall, and that can happen if the header is a broken mix of overlapped joust rails and noggin in-fills. 

Edited December 29, 2020 by Nickfromwales

[Nickfromwales]

Different if it’s just a stud wall above, but clearly a lot more going on here. 

[ProDave]

Just now, Nickfromwales said:

Because the pozi joists don’t take the load   They stop and start at the beam on purpose as they have no compressive / load bearing qualities at the tail ends. The above listings need to be transferred directly to the load bearing stud wall, and that can happen if the header is a broken mix of overlapped joust rails and noggin in-fills. 

There are multiple ways of designing a structure to do the same thing.  Our posi joists are made with a solid timber section between the top and bottom chords at the end to they do sit on top of the wall and do take a compressive load on the end.

 

but I think we have established in this instance the glulam is in compression, not being used as a beam as such, so subject to confirming with the engineer just for comfort there should be no issue drilling it.

[Nickfromwales]

5 minutes ago, ProDave said:

Our posi joists are made with a solid timber section between the top and bottom chords at the end to they do sit on top of the wall and do take a compressive load on the end.

Yes, but that’s only permissible up to a certain weight / load. 

[ProDave]

9 minutes ago, Nickfromwales said:

Yes, but that’s only permissible up to a certain weight / load. 

It would be interesting to know just what is above that beam.

[Nickfromwales]

19 hours ago, LA3222 said:

The wall running along my kitchen is load bearing and takes the weight of a wall directly above. The wall above carries three point loads, the ridge beam and purlins supporting the roof and transmits this load down through to the foundations.

  

[ProDave]

16 minutes ago, Nickfromwales said:

The wall running along my kitchen is load bearing and takes the weight of a wall directly above. The wall above carries three point loads, the ridge beam and purlins supporting the roof and transmits this load down through to the foundations.

So no different to the load on my walls that are fine with the posi joist ends in compression.

 

As a say, many ways to skin a cat.

[LA3222]

8 hours ago, ProDave said:

The Glulam is not acting as a beam in the conventional way with a support at each end and a load in the middle.  It appears to be in compression (vertically) supporting the load above down onto the load bearing wall, and that bit of it to me suggests you could cut a dirty great hole in it without anything falling down.

The timber being in compression and not tension is also what makes me thinking cutting a hole in it is not an issue.

 

8 hours ago, Nickfromwales said:

The glulam is used here for plug n play construction IMO as two bits of C24 would likely need to be packed and trained into position due to natural timbers instability. Glulam beams are inherently flat, straight and uniform, when pre-cut and sent as part of a TF kit. They’re usually oversized in length and trimmed during installation in this type of instance. 

I suspect this is a lot of the answer as to why the glulams were used. They were used in this role everywhere in my build. In one room I mentioned that it blocked the passage of services and was told I could hack it to my hearts content as it pretty much only supported the floor deck above.  Its the fact there is a load bearing wall above this one which makes me hesitant to rush into cutting holes!

 

7 hours ago, Mr Punter said:

To play safe, install a couple of vertical 38 x 89 studs in the wall under and ask the TF engineer to confirm this is acceptable.  

This is a good shout and something I'm happy to do as belts and braces regardless. I had another look earlier and to the right, (about 1m away from where i want to core) there are 5 studs together in a direct path from the point load of the purlin above so I don't see the hole I want to make affecting that.

 

7 hours ago, Mr Punter said:

It is this large build up of horizontal timber that causes shrinkage in timber framed buildings, but it is the standard way of doing things.

And this is probably the final piece of the puzzle as to why it is done this way. I have a SIP build, superdry timber is used throughout so that the shrinkage is minimal. I suspect the use of glulams here helps a lot with keeping shrinkage down.

 

 

Out of interest, I've attached a picture of how the joists sit on the glulams:

 

 

 

Edited December 29, 2020 by LA3222