On May 20, 11:24*pm, wrote:
On 20 May, 15:11, RobertL wrote:
I want to support my ground floor joists. This is partly to take the
weight of a piano and also because the joists do deflect rather a lot
anyway when weight is put on them (such as bookcases, cookers etc.
The joists in these houses (8"x2" at 18" centres) are, apparently, of
rather poor quality and have shrunk and bent in every house in eth
development. They were built in 1964 - part of the "Span House"
movement. *When the floor deflects the walls that are built on it (of
block) move and crack which is not nice.
Under the house the gap between the earth to underside of each joist
is about 50cm. *This is too big for a car scissor jack - I had
imagined using a row of scissor jacks. *It's too small for an ACROW
prop.
One simple solution is to use some wooden 4"x2" props with carpenter's
wedges to adjust the height. *But I am worried about creating a damp-
conducting path up to the joists even if I stand the base on damp
proofing membrane.
Does anyone have any other suggestions?
Robert
Dear Robert
You do not state what span these joist are at. *In a house of that age
the oversite "should" have been concrete. If it is not then you need
to found whatever you decide to use on a suitable base.
I am guessing that with 8" x 2" joists you have a decent sized room
say 20' long... so you need to halve the span. This really can only be
done sensibly as follows:
get yourself some decent sized concrete blocks and bed on the oversite
or if that is friable on the ground dug up under the oversite (ie dig
down to a solid-ish substrate) and fit the blocks at appropriate
centres - say 6' or so accross centre span. This is likely to be say
one each side of the room and two or possibly three in the middle.
Use the blocks to build up brick piers or if you so wish to use trench
acrows - which would be more expensive and prone to rust but much
quicker
If you do use them - liberally cover in red lead or the equivalent now
that has been banned.
Surmounting the piers or on top of the trench acrows should be a
decent sized wall plate say 4" x 4" which in the case of the acrows
can be screwed up but if you accept my and the others' suggestion of a
brick pier 9" x 9" - once fully set and strong (7 to 10 days with 3:1
sand cement mortar) then use slate wedges to pack up each plate to the
joists. Have a layer of dry pack in between slate lamina so there are
no slip planes
Lastsly, screw or nail joists to plate and supplement this with solid
strutting further *to stiffen the structure
Chris G- Hide quoted text -
- Show quoted text -
Thank you for this very detailed suggestion Chris. I'll try
diggindigging down to see if i find concrete or earth. I already
removed a lot of old rubble and 1960s cigarette packets etc. I
suspect the underneath of the houses was used as a dump by the
builders for old materials and that there may well be a conrete layer
a little further down. Clearly a form bedding is needed for whatever
solution I adopt.
The span is about 15 feet. ironically the style of housing is called
"Span House". Here's an example of the type of house (though mine has
a pitched roof on it and looks much nicer).
http://www.propertyfinder.com/cgi-bi...o&id=502649078
Robert