Chemical anchors for ledger beam

danlightbulb · 30 Jan 2024 at 12:48

Im going to be installing a ledger beam on a brick wall to hang additional loft joists off for improving my loft storage. Hoping to use 6x2 ledger beam and same size joists. It all needs measuring up still.

Ledger beam will be fixed to brick and I want to use chemical anchors with threaded bolts, nuts and large washers.

What size and length bolts do I need, how much of the bolt needs to be within the brick?

The joist will be 2" thick (actual dimension I think is around 45mm), and I'll need some thread protruding for the washer and nut, so that is at least say 65mm sticking out from the wall to be safe. How much thread in the wall and what diameter bolts do you think?

a lot of the anchor bolt threaded rods look to have a section where there is no thread on. Not sure why, but if this section happens to land where the surface of the material is, then obviously it won't be able to be tightened properly.

Thanks

Hagar · 30 Jan 2024 at 16:14

You can download a design app for hilti chemical anchors from their website. All other makes will be similar. Personally I would use angle cleats drilled for the anchors seated below your timber ledger beam. This will produce an attached thickness of less than 10mm and probably an embedment of 90mm into the brick or block.
The cleats could be coach bolted under the beam which is restrained from rotation be the joists above.

M12 would be a suitable diameter. Maybe a little less

danlightbulb · 30 Jan 2024 at 16:26

Hagar said:
Personally I would use angle cleats drilled for the anchors seated below your timber ledger beam

These?

Sabrefix Heavy Duty Angle Brackets Galvanised 60mm x 50mm 10 Pack - Screwfix

Order online at Screwfix.com. 2mm thick. Can be secured with nails, screws or bolts. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Not sure I like the idea of the ledger beam only being secured through the bottom of it into these brackets. I could face fix as well I suppose, but I think several bolted face fixings should be sufficient.

Hagar · 30 Jan 2024 at 16:34

danlightbulb said:
These?

Sabrefix Heavy Duty Angle Brackets Galvanised 60mm x 50mm 10 Pack - Screwfix

Order online at Screwfix.com. 2mm thick. Can be secured with nails, screws or bolts. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Not sure I like the idea of the ledger beam only being secured through the bottom of it into these brackets. I could face fix as well I suppose, but I think several bolted face fixings should be sufficient.

In my mind I was thinking a 300mm length of 50 x 75 x 10 RSA, 75m leg vertical and drilled with at least 3 holes to suit your bolt. This avoids timber bearing onto a through bolt however I do not know your loadings.

Good luck with the project anyway.

danlightbulb · 30 Jan 2024 at 17:17

Hagar said:
n my mind I was thinking a 300mm length of 50 x 75 x 10 RSA, 75m leg vertical and drilled with at least 3 holes to suit your bolt. This avoids timber bearing onto a through bolt however I do not know your loadings.

Oh i see, any links to something like that, I wouldn't have a clue where to even go to buy it.

Essentially youre saying make the main loading point out of steel rather than wood. Then the wood sits on that. Like a gallows bracket.

The load still sits on bolts though, ultimately, just through the steel not the timber.

danlightbulb · 30 Jan 2024 at 17:18

Hagar said:
owever I do not know your loadings.

The way the floors are in this house, whatever I build will likely be stronger than what's already in the main house.

Hagar · 30 Jan 2024 at 18:29

danlightbulb said:
Oh i see, any links to something like that, I wouldn't have a clue where to even go to buy it.

Essentially youre saying make the main loading point out of steel rather than wood. Then the wood sits on that. Like a gallows bracket.

The load still sits on bolts though, ultimately, just through the steel not the timber.

Yes if the load acts through the centre of the steel 5mm from the wall rather than 25mm from the wall through the timber it is less eccentric. Some screws just to hold it on the bracket and skew nailing the rafters at the top for a bit of stability.

As for where to find it, I was more used to getting it fabbed up at work. Maybe a little local fab shop. Again I don't really know how much load that is going to attract which would size up what you need better.

danlightbulb · 30 Jan 2024 at 18:42

Hagar said:
Yes if the load acts through the centre of the steel 5mm from the wall rather than 25mm from the wall through the timber it is less eccentric. Some screws just to hold it on the bracket and skew nailing the rafters at the top for a bit of stability.

As for where to find it, I was more used to getting it fabbed up at work. Maybe a little local fab shop. Again I don't really know how much load that is going to attract which would size up what you need better.

Thanks, wouldn't know where to start though with getting something fabricated, I'm not a builder who would regularly buy rsj's. Off the shelf stuff only.

Screwfix do M12 X 160mm or M16 X 190mm threaded studs. I'm thinking M12 would be ok, maybe 90-100mm in the brick leaves me with 15mm free after the width of the timber. Would put in probably 3 per meter of length so roughly one fixing per foot.

danlightbulb · 30 Jan 2024 at 19:27

Hagar said:
Again I don't really know how much load that is going to attract which would size up what you need better.

I've been working on assumption of 0.5 kN/m2 dead load and 1.5 kN/m2 imposed load as per the joist span tables. 6x2 joists at 400mm centres allow me a span of 3m which is what I need roughly, although it all needs measuring up properly. For loft storage I think this should be fine.

Only one end of the span needs a ledger beam, the other end will be supported on an internal supporting brick wall.

Hagar · 30 Jan 2024 at 20:33

danlightbulb said:
I've been working on assumption of 0.5 kN/m2 dead load and 1.5 kN/m2 imposed load as per the joist span tables. 6x2 joists at 400mm centres allow me a span of 3m which is what I need roughly, although it all needs measuring up properly. For loft storage I think this should be fine.

Only one end of the span needs a ledger beam, the other end will be supported on an internal supporting brick wall.

Your loadings sound good to me. Typical domestic floor loads I believe.

danlightbulb · 30 Jan 2024 at 21:24

Hagar said:
Your loadings sound good to me. Typical domestic floor loads I believe.

Yeah lots of information around on joist sizing, can't find much on ledger beam fixings though. Tried that Hilti app, it doesn't tell you how many or what size of fixings you need.

Hagar · 30 Jan 2024 at 23:14

danlightbulb said:
Yeah lots of information around on joist sizing, can't find much on ledger beam fixings though. Tried that Hilti app, it doesn't tell you how many or what size of fixings you need.

Aah, it is seven years or more since I last used it in anchor designs but they had one where you input the anchor layout, number etc., added the applied loads, direct axial, shear etc and the anchor type and it churned out capacities etc. SPLIT is another supplier and Fischer I think.

danlightbulb · 31 Jan 2024 at 01:05

Hagar said:
Aah, it is seven years or more since I last used it in anchor designs but they had one where you input the anchor layout, number etc., added the applied loads, direct axial, shear etc and the anchor type and it churned out capacities etc. SPLIT is another supplier and Fischer I think.

Yeah if you input the number of anchors etc it tells you how much resin you need, but it doesn't tell you how many fixings or what length of fixings you need for what size joists/load.

Mercenary Keyboard Warrior · 31 Jan 2024 at 08:48

Fischer used to be the go to brand of the fixings expert when I worked for a large (UK national) construction supply company.
Things could have changed but they were he always claimed the best.

Personally I wouldn't over think it.
Get some decent fixings deep into the bricks and when your installing double up with a good dose of grip fill type building adhesive (solvent based) to help reinforce the fixings.