Floor joist notching

[SaladFingers]

On a house where the downstairs floor sits on 4" joists which are stood off a concrete area below by several courses of bricks, can they be notched by 25mm?

Those joists only support the floor and nothing else above structurally.

 

[freddiemercurystwin]

No http://www.eastdevon.gov.uk/bc-guidancenote7-notchingofjoists.pdf

 

[SaladFingers]

Roger, just as I thought.

I've come across some 4" floor joists with some notches. What can I do to ensure they're as strong as they need to be? Could I fix some 3x2" along the side to ensure everything is fine?

 

[tony1851]

It depends where along the span you notch them. If the notch is fairly near the end it would not be a problem.
If your notch is near the middle, you will be effectively turning it into a 3" deep joist and you may have problems.

 

[SaladFingers]

Ok, effectivly what sort of problems am I going to get? Will it make that much of a difference? It's not every joist though. Ought I to add something to the side of them to brace them up a bit?

 

[freddiemercurystwin]

May bounce a bit, theoretically it could snap if you eat too many pies, depends on the spans, centres, loadings and strength of the wood. Add a 3x2 to the side of the ones you intend to notch if you want to.

 

[SaladFingers]

May bounce a bit, theoretically it could snap if you eat too many pies, depends on the spans, centres, loadings and strength of the wood. Add a 3x2 to the side of the ones you intend to notch if you want to.

I'll brace it up then where notched.

What's the best approach, coach screw the bracing timber on or drill through and use bolts and nuts?

 

[HERTS P&D]

Use timber both sides of joists and bolt straight through, use long lengths of timber.

http://www.ebay.co.uk/itm/10-LENGTH..._MJ&hash=item2c5403252a&_uhb=1#ht_4775wt_1271

Andy

 

[tony1851]

Mr Fingers[
1. What is the span and spacing of your 4" deep joists?
2. How far from the end of the joist will the notch be?
3. will the notch be top or bottom, and how wide will it be?

 

[SaladFingers]

The spacing is 450mm centre.

Notches are 25mm at the top.

Span is from sleeper wall to sleeper wall, 2.8 meters and the notches are at 85cm and 1m.

 

[tony1851]

If the clear span sleeper wall to sleeper wall is 2.8m, I suspect your 4" joists are already over-spanned. I usually work off the old (pre-TRADA) span tables, which are more generous than allowed now, and even these show only 1.87m for 4x2 @450 centres.
Also, your notching is not that near the end, and you will therefore be effectively weakening the joists further. If you have to notch on alternate joists, do as the others have suggested and strengthen with 3x2 glued and screwed on the sides. These pieces do not have to go the full span of the 4x2 - 4 or 5 ft long pieces would be OK so long as they are firmly fixed.

 

[SaladFingers]

Would another acceptable method be to build sleeper posts under the joists where the nothces are?

 

[tony1851]

If the sleeper walls were near the notches, that would certainly solve the problem, but it would be a lot of work.Wouldn't it be easier to strengthen the joists?
Just a thought; if the gap under the floor is not too much, could you just support the notched joists with concrete blocks with some dpc material under the joists? What is the height between the concrete and underside of the joists?

 

[JohnD]

if you have sleeper walls, why to you feel the need to notch the joists?

what are you planning to put in the notches?

 

[SaladFingers]

The joists are already notched. I'm looking at what do to about it.