Maximum joist length?
 

Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Is this feasible? 7 metres sounds like a very long span unsupported,
assuming that you can even get 7 metre long joists? I would have thought
that at least one cross beam would be needed for such a span.

I'm happy to lay floorboards and do the associated DIY but I'm no
structural engineer!

Suggestions?

--
David in Normandy.
To e-mail you must include the password FROG on the
subject line, or it will be automatically deleted
by a filter and not reach my inbox.

Maximum joist length?
 

"David in Normandy" wrote in message
. fr...
Someone has asked me to help put in an upper floor in a farm outbuilding.
The room dimensions are 7 metres by 5 metres constructed with a single
thickness of breeze blocks. He is planning having 7 metre long joists and
fixing down traditional tongue and groove floorboards on top.

Is this feasible? 7 metres sounds like a very long span unsupported,
assuming that you can even get 7 metre long joists? I would have thought
that at least one cross beam would be needed for such a span.

I'm happy to lay floorboards and do the associated DIY but I'm no
structural engineer!

Suggestions?

Engineered joists will do it (just).

http://www.jji-joists.co.uk/index.ph...ive_span_table
for example.

Maximum joist length?
 

On Thu, 23 Jun 2011 19:43:13 +0200, David in Normandy wrote:

Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Our 2nd floor (22mm chip on top, plasterboard underneath) is
supported by 7 x 2 joists at normal spacing and it is, erm, "bouncy".
These joists are
only 4.5m long...

Gut feeling is that 7m is going to need some seriously chunky bits of
timber, 8 x 4, 8 x 6? they won't come cheap in 7m lengths.

Why doesn't he use the 5m dimension for the joists?

--
Cheers
Dave.

Maximum joist length?
 

On 23/06/2011 18:43, David in Normandy wrote:
Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Is this feasible? 7 metres sounds like a very long span unsupported,
assuming that you can even get 7 metre long joists? I would have thought
that at least one cross beam would be needed for such a span.

I'm happy to lay floorboards and do the associated DIY but I'm no
structural engineer!

Suggestions?


Table A of the Building Regs suggests a 9 x 3 will only span about 5.5m,
so probably no.


--
Dave - The Medway Handyman www.medwayhandyman.co.uk

Maximum joist length?
 

On Jun 23, 6:43*pm, David in Normandy
wrote:
Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Is this feasible? 7 metres sounds like a very long span unsupported,
assuming that you can even get 7 metre long joists? I would have thought
that at least one cross beam would be needed for such a span.

I'm happy to lay floorboards and do the associated DIY but I'm no
structural engineer!

Suggestions?

--
David in Normandy. *
* *To e-mail you must include the password FROG on the
* *subject line, or it will be automatically deleted
* *by a filter and not reach my inbox.

Is there some earth-shattering reason for not laying the joists in the
5m direction?

Maximum joist length?
 

Maximum joist length?
 

On Jun 23, 8:03*pm, "Dave Liquorice"
wrote:
On Thu, 23 Jun 2011 19:43:13 +0200, David in Normandy wrote:
Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Our 2nd floor (22mm chip on top, plasterboard underneath) is
supported by 7 x 2 joists at normal spacing and it is, erm, "bouncy".
These joists are
only 4.5m long...

8 x 2 (250*50mm) would be to code for 4m span, 400mm spacing - I
think, for domestic floor loads.

Gut feeling is that 7m is going to need some seriously chunky bits of
timber, 8 x 4, 8 x 6? they won't come cheap in 7m lengths.

Depth is what counts. Strength is proportional to square of the depth,
Stiffness is cube of the depth.

Why doesn't he use the 5m dimension for the joists?

--
Cheers
Dave.

Maximum joist length?
 

In article , David in
Normandy writes
Someone has asked me to help put in an upper floor in a farm
outbuilding. The room dimensions are 7 metres by 5 metres constructed
with a single thickness of breeze blocks. He is planning having 7 metre
long joists and fixing down traditional tongue and groove floorboards on
top.

Is this feasible? 7 metres sounds like a very long span unsupported,
assuming that you can even get 7 metre long joists? I would have thought
that at least one cross beam would be needed for such a span.

I'm happy to lay floorboards and do the associated DIY but I'm no
structural engineer!

Suggestions?

Might be a job for engineered joists but even then 5m sounds better than
7m which I suspect could get a bit expensive and bouncy.

This came up on a quick search (engineered joist span):
http://www.trussform.co.uk/
Useful data here on spans and rigidity:
http://www.trussform.co.uk/download/...ical_Guide.pdf
Note plenty of options at about 5m diminishing towards 7m.

Not local to you of course but I'm sure there will be outfits in France
too.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

Framing a lean to
 

I am building a lean to in the UK
Length 27' x death 8' x height 8' with a slope for the roof upto 10'
I am considering using 2" x 4" for all the Framing with 16" between each uprights.
Again for the rafters I was thinking of using the same wood 2" x 4" at 9' lengths to allow for some overhang.
Does anyone have any concerns or suggestions

Framing a lean to
 

On 23/07/2020 09:51, wrote:
I am building a lean to in the UK
Length 27' x death 8' x height 8' with a slope for the roof upto 10'
I am considering using 2" x 4" for all the Framing with 16" between each uprights.
Again for the rafters I was thinking of using the same wood 2" x 4" at 9' lengths to allow for some overhang.
Does anyone have any concerns or suggestions

Perhaps more uprights than you need? With a bigger support at the lower
end, say a 6x2, you might get away with uprights at say 48 inches
(although I would be inclined to use 4x4 uprights).

What roof material? Is this in an exposed or windy area? What about snow
load?

You'll need some diagonal bracing for the outer "wall", I think; A
suitable roofing material would provide diagonal bracing for the roof plane.

Framing a lean to
 

On 23/07/2020 09:51, wrote:
I am building a lean to in the UK
Length 27' x death 8' x height 8' with a slope for the roof upto 10'
I am considering using 2" x 4" for all the Framing with 16" between each uprights.
Again for the rafters I was thinking of using the same wood 2" x 4" at 9' lengths to allow for some overhang.
Does anyone have any concerns or suggestions


really depends on the weight of the roof covering. Will it be
tiled with artificial slate or marley concrete tiles or something
lightweight like epdm ? . You might have to go up to 6x2 for the
rafters.

The manufacturers of whatever hard roofing you choose should have
tables on their website showing the amount of overlap neeed for
your 12? degree pitch. There are limited tile choices for a
pitch that low, eg


https://www.jjroofingsupplies.co.uk/...umpitch_ln=567

Framing a lean to
 

On Thursday, 23 July 2020 11:44:40 UTC+1, Andrew wrote:
On 23/07/2020 09:51, wrote:

I am building a lean to in the UK
Length 27' x death 8' x height 8' with a slope for the roof upto 10'
I am considering using 2" x 4" for all the Framing with 16" between each uprights.
Again for the rafters I was thinking of using the same wood 2" x 4" at 9' lengths to allow for some overhang.
Does anyone have any concerns or suggestions


really depends on the weight of the roof covering. Will it be
tiled with artificial slate or marley concrete tiles or something
lightweight like epdm ? . You might have to go up to 6x2 for the
rafters.

The manufacturers of whatever hard roofing you choose should have
tables on their website showing the amount of overlap neeed for
your 12? degree pitch. There are limited tile choices for a
pitch that low, eg


https://www.jjroofingsupplies.co.uk/...umpitch_ln=567

though there are ways round those limits to some extent.