Joist sizes in a 1930s build

[curium]

Hi All,

I'm back with more amateur questions

Just some history, the previous occupants glued ply onto the floorboards and then glued vinyl tiles to the ply (Removing laminate glued to ply glued to floorboards - nightmare). This has made getting access difficult and the trades have understandably told me to get back to them once it's done.

I have managed to get a section of my flooring up in order to provide access to plumber & electrician.

This has revealed the joists which seem solid enough and the oversite is dry.

My question concerns the size of the joists. At my previous property (a new build) the joists (revealed after a bathroom leak) seemed a lot deeper, 150mm at a guess.

These joists are 3.5" (89mm) deep and 1⅞" (48mm) wide. It'll certainly reduce the amount of PIR insulation I can wedge in between to 75mm.

My question: Is this standard in a 1934 property?

Cheers

 

[blup]

Mine are 4x2 in a 1930's property, about a 5 metre span IIRC.

Blup

 

[curium]

Mine aren't even 4x2, that would be 3¾" deep.

Another question: I've not encountered previously the type of nails used to secure the floorboards. Anyone know what they're called?



Should I be concerned about the splits along the top of the joists as I'm pulling up the boards and nails?

Cheers

 

[jacko555]

My 1920s property has 4x2-ish downstairs with mid span dwarf walls, and 7x2 upstairs. 4 or 5 m spans, a few longer upstairs.

That nail is a brad (As I know them)

No idea what's "standard" for 100 yrs ago, I think it was more a "that'll do" attitude

 

[Deleted member 174758]

That nail is a brad (As I know them)

View attachment 243291

Just goes to show local differences; I was brought up to call them "cut nails" (because they are cut or punched out from a ribbon of rolled steel). They are still in use, at least in my part of the world, because they are less likely to split softwood floorboards than either "French" (round wire) nails or oval nails. To me a brad means a smaller nail these days

As to joist sizing the very rough rule of thumb in houses is the that the depth of joists, on 16in centres with ex-2in thick stock, in normally about 1/25 of the length - so for a 5 metre (roughly 15ft) clear unsupported span I'd expect around about 7 x 2in timbers. Any money there is some form of intermediate support beneath that floor. If not it might be a tad bouncy, although gluing chipboard onto it and adding solid strutting would cure that - to an extent

 

[curium]

The joist span is 1.6 metres. It's in the entrance hallway with a solid brick wall either side.

The joist centres vary from 13½" to 14½".

 

[Deleted member 174758]

The narrow joist centres would certainly allow you to get away with smaller section timbers, but not that much smaller. I still wonder if gluing the floor down was done was a response to bounciness in the floor - and did it cure that (i.e. is the floor still bouncy, or is it firm?). How thick is the surface above the planking? How thick are the original planks?

BTW splits can happen. Unless they are very deep I wouldn't worry about them.

 

[tony1851]

Mine are 4x2 in a 1930's property, about a 5 metre span IIRC.

Blup

4x2? 5m span? That's not floor - it's a trampoline

 

[tony1851]

My 1920s property has 4x2-ish downstairs with mid span dwarf walls, and 7x2 upstairs. 4 or 5 m spans, a few longer upstairs.

That nail is a brad (As I know them)

View attachment 243291

No idea what's "standard" for 100 yrs ago, I think it was more a "that'll do" attitude

They were difficult for the joiners to use as they could result in cut fingers due to the sharp edges - gloves were adviseable. They were less liable to split the wood as they tended to chisel through the grain, rather than force it apart as wire nails can do.

Today they are frequently used to nail skirting boards to lightweight concrete block (eg Celcon, Thermalite etc) as they have far greater holding power than the smooth finish of round wire nails or ovals.

 

[Deleted member 174758]

Not so much "were", Tony, as "are" - we still use them for some flooring (albeit not a lot). Certainly on bigger sites gloves are mandatory these days, and have been for maybe 10 years(?), so anyone with half a brain in their head it shouldn't tax them too much to understand why one need to wear gloves whilst handling timber and metal

 

[blup]

4x2? 5m span? That's not floor - it's a trampoline

Rafters not joists

Blup

 

[tony1851]

Rafters not joists

Blup

Thank goodness for that.....!

 

[JP_]

4x2s in my 1934 Essex bungalow, all rooms have a central dwarf wall to help support, to span only 1.7m at most, often less in smaller spaces.

I've pulled out about a million of those. I screw the boards back down again with those posi something star or hex head screws