Piece of slate or several layers of roofing felt folded over or a couple of layers of heavy-duty polythene damp-proof membrane.
Any one of them, preferably the last, on top of the pillar and up against the underside of the joist.
No. It's much simpler.
Just put a layer of DPC under the joist as you pack the mortar in on the top and last brick course.
Or you can put the DPC between a course of bricks - does not really matter but for small stubby pillar, having a DPC between the bricks will be a weak point.
A small 8x8" brick pillar under the midspan will help the joist enormously (in fact it will make it about 4 times better in terms of strength and probably similar WRT sag.
The other solution is to put some noggins between the joists to spread the load to its neighbours.
Or he could spend £6 on the right stuff which is far simpler :)
If you've got a car-type bottle jack, use that to jack the joist up slightly when packing it. That way, it will sit firmly on your new pillar when you remove the jack.
[Depending on the height, you *could* possibly use a screw (not hydraulic) jack as a permanent support to save having to build a pillar- or a mini Acrow prop if it's too high for a jack.]
Actually, if the first joist is close to the wall, some of the weight of the piano will almost certainly be supported by the second joist too. So, if you put a stout piece of timber under both joists at right angles to them, and jacked under the middle of that, you could kill two birds with one stone!
We have an upright piano which, due to its weight is causing a sag in the suspended wooden floor (50's semi). Only 1 joist is really affected as the piano is aligned lengthwise along it. It is the first joist in the room - adjacent to the wall. As I have to replace some floorboards (for unrelated reason) I thought to build a short brick pillar to support this joist at the same time. How can I do this without getting a path for damp from the concrete upwards? Should I put one layer of eng brick in there? I think I can do the work if I have some instruction on what to actually do! Thanks.
Place a piece of damp proof membrane under the bottom bricks and the same on the top bricks, so any damp can't rise above those barriers.
Or use a decking pedestal ,example on this site.
Small quantities are often available on ebay such these at time of writing.
G.Harman
In message , snipped-for-privacy@yahoo.co.uk writes
One thing I like about this group is seeing things that it never occurred to me even existed. I didn't know about scutch hammers and chisels until that thread up there ^, either.
Of course if the piano could be positioned across more than one joist, its weight might not give quite as much problems to the ceiling underneath, or the floor on top. Just a thought.
Get an electric piano instead? Brian
One of these isn't going to be as strong (stiff) as a brick pier, though.
2nd'd. Thanks all.
I've used those to level up a shed - they are damn good if you have something solid to put them on and the adjustable nature makes them really rather handy.
In your case, if all you have is dirt, sticking one of those on a paving slab to spread the load should be more than good enough.
No - but you'd be surprised how solid they are.
You said you needed to stop sag due to a piano that weighs what, 250-400kg?
One of those midspan will be well within spec - but no harm in doing a brick pillar of you want - it's just the former would be a short job :)
The stability of a pier would be increased if a DPM wasn't used at the base.
There is only need for one, and I would suggest that it is used at the top.
And being plastic would incorporate its own DPM.
Paving slabs are no use for taking load - they just crack across. Get a reinforced concrete lintel from a builder's yard - they're dirt cheap.
Actually, same can be true for concrete subfloor. Unless you know the house was built on a reinforced concrete raft, you might find the concrete is too thin except where it's designed to support part of the structure.
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