I am working on a basement renovation in a house built in 1943. New electrical wiring and RiR for water to the radiators will be installed in/directly under the wooden floor structure. The ceiling height in the basement is limited, ~2.10m, so I've been considering the possibility of skipping the furring strips (28x70) inside the ceiling and instead notching/milling in the beams for electricity and radiator water, approximately 3 cm deep. The floor structure consists of 220x70 beams spaced at CC60 and the span is about 3.5m. The beams rest on the exterior walls and a central load-bearing wall, hence the span of about 3.5m, and the house is about 7m wide.
It doesn't feel right to damage the beams where the tensile forces are the greatest. At the same time, it feels like the floor structure is somewhat over-dimensioned as it is.
Running water and electricity centrally in the beams is also an option, but I would prefer to avoid this as it would require me to empty all the sawdust used as insulation.
Another alternative is to use lighter timber than 28x70, placed directly on the beams, to reduce the depth that needs to be notched.
And if nothing else is feasible, I will use furring strips (28x70) and accept that the ceiling height decreases somewhat.
220x70 corresponds approximately to 255x45 in terms of bending resistance, so it is indeed over-dimensioned. However, it's never good to notch beams as it creates a crack initiation point in the material, the effect of which can be difficult to assess. Drilling holes completely through for pipes as small as those in question here can be done without issue, as long as you stay a few centimeters from the bottom edge. What's best in your case is difficult to determine without seeing the space in person. I also don't think you should scoop out the sawdust. I suggest a bit of lateral thinking. Perhaps you can run the pipes along the wall in a routed groove that doesn't have to be too obtrusive.
Thank you for the response! Yes, it doesn't feel right to notch the bottom of the beams. However, it's problematic to lay the pipes along the wall; it won't look good considering that I need to run supply to 5 radiators in the ceiling as well as electricity and network. The walls are made of concrete hollow blocks and are plastered and partially tiled. If I run the pipes in a channel on the wall, I would also need to go past a few windows and a door.
Here is a picture where you can see the beam structure from below. I have emptied out the sawdust in one section because I need to insert a ventilation duct there for FTX ventilation. You can glimpse the construction in the section to the left. From the bottom up, it consists of tongue and groove wood, paper, and then sawdust. The tongue and groove wood rests on square dowels, roughly 3x3 cm, which are mounted flush with the bottom of the beams. Practically, it would be perfect to use that space to run the pipes.
Do you see any obstacle with emptying out the sawdust besides the fact that it creates a lot of extra work getting new insulation in place and disposing of the sawdust?
Absolutely not! Refilling can be done with, for example, cellulose fibers that have similar hygroscopic properties to sawdust. One should not change such conditions unnecessarily.
Absolutely, I’ll make sure to use appropriate insulation in that case, e.g., cellulose fibers as you suggest. But you don't see any other problems with removing the sawdust?
Anyway, I’m currently leaning towards lowering the ceiling; removing the sawdust seems like quite a lot of work.
I have faced the same problem a few times in my house. Some solutions I have used, either individually or in combination:
- Place all pipes along the outer wall or heart wall. Notches or other weaknesses do the least damage near the supports. Lead the pipes out to the correct place in each compartment.
- If the subfloor boards are loose and not too tightly filled with shavings, try to push up the subfloor boards a few cm with a prop and wedge a piece of wood underneath so you can drill for the pipes a few cm into the beams.
- You don't need to empty the entire beam compartments of shavings. It's enough with a small section where you run the pipes. Knock out a couple of subfloor boards. Refill with shredded insulation that is poked in and packed as well as possible against the remaining sawdust. I have used stone wool, but it should work with cellulose fibers or similar if you are concerned about stone wool.
- If there are places on the floor above where it is easy to open the floor and restore it without it being noticeable, it is easy to refill with the insulation material of your choice. Check for example thresholds, under cabinets, etc.
Jacking out near the editions is a very interesting idea, would work very well for me.