Strengthening a bathroom floor on Bethlehemweg in Utrecht
During the bathroom renovation, the contractor noticed excessive deflection of the timber joists and asked De VerbouwingsConstructeur for advice.
We found:
- Undersized timber joists: 70×150 mm over a span of 4,500 mm, with varying centres of up to 600 mm.
- In the middle of the edge joist on the hallway side, a notch of about 50 x 50 mm. This edge joist also carries extra load from the trimmer joists of the stairwell in the hallway.
- At the end of one joist, two vertical 10 mm diameter holes, which may be a problem for the maximum shear force it can carry.
When these hidden defects came to light, the client considered holding the seller liable. But because the seller would then have to be given the opportunity to remedy the defects, and it was doubtful whether that would happen quickly and properly, the buyer asked De VerbouwingsConstructeur whether there was a cheaper and quicker solution. There was.
Using the contractor’s rebar detector, we found a steel beam on the extension side, belonging to an extension built by the previous owner. From the thickness of the top flange we could tell it was an HEA200 section. With this section and an edge joist (on the hallway side) strengthened with a C160 channel, we were able to create a load-bearing system with Lewis dovetail sheets. Our certified software showed that the deflections and bending moments at mid-span of the joists comply with the standard. The shear forces at the ends of the joists were also low enough for the holes at the end of the timber joist to be acceptable.
Afterwards, the client was pleased and emailed us on 11 March:
“Thank you again for your help and your flexibility at such short notice.”