Bedding timber beam on brick wall

Discussion in 'Wood / Woodwork / Carpentry' started by jcp, 29 Oct 2021.

  1. jcp

    jcp

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    Our chippy has chocked up the ends of the double beams (2 of c24; 170x47mm, bolted together) around our new stairwell with a short small softwood wedge (about 30mm wide) banged in between the middle of the beam pair and the next brick below in the supporting internal brick walk. He has now gone off site in a huff with the voids around the beams unpacked. An unavailability of cement might be to blame!

    I assume the voids should be filled with mortar, or the beams could surely move. Should I ram in a strong dry mix of cement and sharp sand (1:3, like I did between steel beams and in situ cast concrete padstones in earlier projects)? Or are there different rules for restraining timber beams?

    The chippy had earlier said new rules meant he shouldn't really bed timber beams on possibly damp masonary walls, but this was unavoidable in our case. I am concerned the bearing surface of the timber wedge is very small, and it could easily be compressed or dislodged.

    I would be grateful for any advice. There is more to the story, but this is probably enough for now!
     
  2. JobAndKnock

    JobAndKnock

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    He's right about the powers that be no liking timbers going into walls - we've routinely had to use pressure treated timbers and envelope wrap the ends of beams/joists with felt before installing them (listed buildings, so not always avoidable). In the main ours go onto a cast-in situ concrete pad stone, but in some cases the brickies prop the timbers, knock out the wedges and pack the voids beneath with slate cuts or brick slips and mortar. Side gaps are packed with brick offcuts and mortar as well
     
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  4. jcp

    jcp

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    Thanks for those comments.

    Actually, our work is also on a listed building (from around 1690, and based on a cruck frame) - I did say there was more to the story!

    However, we are focussing on an old lean-to byre that was improved over the years and eventually opened up to the main cottage just before the listing was finalised in the 1980s. As such, it is essentially a modern wing (concrete floor, dpc, gypsum plaster etc), and lies outside the listed part of the building. Providing we don’t damage or detract from the old part of the cottage, we can improve the old byre. Thus, amongst other things, the old and very steep staircase, is being replaced with a building regs compliant staircase, in a larger and slightly shifted stairwell, with a new trimmer beam that still bears on the byre’s old (but previously rebuilt) masonry wall. Meanwhile, previous owners had built a first floor bathroom flying out about 2 metres over that rebuilt masonry wall - which is therefore dry and protected from rain.

    If I’ve not turned you off with all that stuff, I think I’m saying the brick wall should be dry. The building inspector has seen the beam works, and has not commented, but I worry the wedge could be dislodged (by vibration, etc). The design bearing force on the wedge is just over 200kg. Would it be wrong to mortar (with brick or slate chips as you describe) around the beam, to keep everything in place. I don’t think the building inspector will check again, but I also doubt a significant moisture path to the timber would be created.

    Thanks again for your comments
     
  5. JobAndKnock

    JobAndKnock

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    We have done just that in places on the last few listed buildings I've worked on (a Victorian solid brick-built mill complex, a block of large stone-built Victorian shops and another, older stone-built mill). As a chippy we set the beams or joists, and maybe half the time we have break-out the masonry to allow us to do this - the making good, however, is always done by the brickies. In general they don't seem to like putting a deep bed of mortar beneath joists and invariably use brick fillets or slate slips in addition to mortar. Sometimes we are required to insert replacement timber spreaders, which look like like a short timber lintel which runs beneath a beam end and is embedded into the masonry. These are invariably a very rot-resistant timber - the lkast ones I did were plantation grown teak. TBH I am not certain whether this aversion to deep mortar beds is being don just for aesthetic reasons (often enough the brick walls we deal with are being left bare) but mortar with slate slips was at one time a common enough way to bed structural steels
     
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