Dale, it seems to me that the simplest and most cost effective way to stiffen
up your floor would be to sister dimension 2 by 8 lumber on to the existing
rough cut 2 by 8 joists. After jacking and leveling each joist you could glue
and bolt the dimension 2 by 8 beams to the rough cut joist keeping the bottom
edges parallel, thus keeping the sub floor baring on the original joist. You
could relocate heating, plumbing and wiring to a chase along the edges of the
usable space to preserve head room in the center of the basement. An
alternative would be to replace the existing joists with an engineered joist
system with an open web, however engineered joist usually are from 10 to 18
inches deep, which would compromise your existing head room.
----- Original Message -----
From: Dale Leavens
To: blindhandyman@yahoogroups.com
Sent: Saturday, October 03, 2009 9:41 AM
Subject: [BlindHandyMan] stiffening inadequate floor joists?
Hi,
It is too wet outside to do any work and I am contemplating a problem I have
had since moving into this old building.
The original house has floor joists rough sawn but only 2 by 8 on 24 inch
centers. We have a springy and uneven floor. Some of it is also because at some
point one of the heating systems required framing in a big cold air return and
they clearly didn't shore up the floor when cutting that joist, someone long
since removed all of the cross bracing.
I don't see sistering or adding joists in the usual way because of plumbing,
wiring and duct work and I don't want to add more posts and beams. It recently
struck me though that I could build in place an open web joist, jack things
temporarily up then fix the lower cord. This lead me to think perhaps a better
way might be to jack tings up just a little above the desired point then apply
a web of strap steel to either face of the existing joists on the diagonal. A
series of 'V's so that the diagonal essentially forms triangles. This would
allow me to continue to respect wiring.
More stiffening might be achieved by running a length of angle iron along the
top inside corner against the floor and the joist and run a bolt through it and
the straps and similarly at the bottom of the joist, I wonder how much would be
enough and how much too much. At some point it might be better to fabricate
individual steel webbed joists and fit them between the originals but then they
may serve the purpose of lifting the originals which would continue to be
pulling down after nearly a century.
Just kicking around ideas. I would like to preserve as much open space there
as I can.
I don't have reasonable access to engineering or architectural services.
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