time in loft

[andy]

doin a re-wire soon. however, the loft is to be boarded to ill have to out wires in joists. question is, roughly how much extra time would this take?

 

[ban-all-sheds]

How big is the loft?

How many cables?

How many joists?

What size holes?

How sharp is your flat bit/holesaw?

How powerful is your drill?

How easy is access?

How fast a worker are you?

 

[andy]

How big is the loft? fairly large, easy access, plenty head room for area where most work will be done

How many cables?

3 bedrooms, landon and bathroom

How many joists?

quite a few. about normal distance apart

What size holes?
25mm

How sharp is your flat bit/holesaw?

good enough. doesnt take long to drill a hole

How powerful is your drill?

800W. doesnt take long to drill a hole

How easy is access?

easy.

How fast a worker are you?

fairly fast. takes about 15 mins to wire a normal loft including alarm.

my guess is that itll take about 1 1/2 - 2 hour extra. just wondering who long it takes you (if youve had that situation before)

 

[felix]

Allow extra time if you have to pick your way through several inches of insulation with an inch-thick layer of dirt on top! Been there, done that. Allow two hours extra for a bath and a Carlsberg Special afterwards.

 

[andy]

Allow extra time if you have to pick your way through several inches of insulation with an inch-thick layer of dirt on top! Been there, done that. Allow two hours extra for a bath and a Carlsberg Special afterwards.

lol

there isnt much insulation, altho ive seen about 1M of fibregass ontop of 150mm of polystryne bits. took over 1H to fight my way thru it!

 

[GrantF]

the loft is to be boarded to ill have to out wires in joists.

What about running batons transversely across the joists to raise the floor an inch or two, and leave the cable on top of the joists. Means you dont have to cut away and weaken the joists?

 

[andy]

What about running batons transversely across the joists to raise the floor an inch or two, and leave the cable on top of the joists. Means you dont have to cut away and weaken the joists?

i kno what your thinkin and i will consider it. altho ill prob drill the joists and run the cables thru there

 

[felix]

A joist is under compression at the top and tension at the bottom. For minimum loss of loadbearing capability drill your holes exactly half way down.

 

[oilman]

A joist is under compression at the top and tension at the bottom. For minimum loss of loadbearing capability drill your holes exactly half way down.

Depends how close to a support you are drilling. if you're near a support, notching is recommended as there's more shear force than bending. Better to lift all the wires above the floor and clip to purlins (unless it's a trussed roof I suppose. Wouldnt drill OR notch if it is.

 

[dingbat]

It is rarely recommended to drill or notch top floor ceiling joists. Unless specified at build it's unlikely they are intended to be load bearing. Why not run cable between joists (clipped to sides) to accessories and take the cable out to the joist binders for the transverse runs? (Between binder and eaves there is insufficient headroom to make boarding worthwhile anyway.)

This doesn't add a great deal to the total cable run, is much quicker than drilling, doesn't degrade the properties of the joists and saves you lugging the drill into the loft.