Building an outbuilding 6x5

[Ali2487]

Hi folks, I have started an outbuilding 6x5, dug the footings today and backfilled concrete. Tomorrow I will be preparing the oversite, checking the foundation levels and the bricklayer will be making a start.

I am giving roofing a try, have most of it figured out but struggling to find a way to fix / tie down the timber to the top of the brickwall. I have found some joist hangers would I could use in an upside down fashion but I doubt this is the correct way.

eg: Joist Hanger

Any guidance or suggestions please?

Many thanks,

 

[robinbanks]

There exists just such a thing for this purpose

Sabrefix Roll Edge Restraint Strap Bend 600mm 5 Pack - Screwfix

Order online at Screwfix.com. Heavy duty galvanised steel. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Can also get twisted ones to strap two surfaces at 90 degrees to each other such as the wall and the side of the joist

Sabrefix Rolled Edge Restraint Strap Twist 600mm 5 Pack - Screwfix

Order online at Screwfix.com. Heavy duty galvanised steel, with 90° twist 100mm from end. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

If you're just talking about the wall plate, can also screw through it and into the concrete block with these:

Easydrive TX Countersunk Concrete Screws 7.5mm x 150mm 100 Pack - Screwfix

 

[Ali2487]

@robinbanks thank you very much this is really useful. I think the twist is the one I want, assuming one strap each side?

That first one you linked, does a strap exist where this is a U shape rather than L shape?

Many thanks in advance

 

[Mr Chibs]

You don't need a twist strap on each joist, maybe 2/3 spaced on the walls where the ends of the rafters/joists are.

The "L" shaped straps go up the wall and the short end of the strap sits on the top of the wall plate to hold it to the top of the wall.
Don't think there are "U" shaped ones.

How are you securing the joists to the wall plate? Nailing, notching, hangers or clips?

 

[Ali2487]

I will be using 6m lengths of wood across the 5m span so should get sufficient overhang. I will be using firring strips so hopefully I won't need any notches etc and should simply be a case of securing down the joists to the wall, which is why I thought I could have two twists straps per joist. I will be using wall plugs and screws to secure straps to walls and open to any advice on whether nails or screws are best for wood.

So I think to answer your question, I wasn't planning on having a wall plate.

 

[robinbanks]

So I think to answer your question, I wasn't planning on having a wall plate.

You showed a picture that featured a wall plate

Take a look at https://harmonytimber.com/wp-content/uploads/2020/02/Cullen-Technical-Guide-Restraint-Straps.pdf for options and guidance

Two straps per joist is overkill

Screws or nails; typically metalwork straps/hangers etc are fixed to structural timber using square twist nails

 

[Ali2487]

Apologies

You showed a picture that featured a wall plate

Take a look at https://harmonytimber.com/wp-content/uploads/2020/02/Cullen-Technical-Guide-Restraint-Straps.pdf for options and guidance

Two straps per joist is overkill

Screws or nails; typically metalwork straps/hangers etc are fixed to structural timber using square twist nails

Apologies, understand how my picture was misleading.

The link you shared all showed pitch roof, would the same apply to flat roofs?

If I am not having a wall plate, am I correct that looks like I want PSB strap with restraint hanger?

 

[robinbanks]

If I am not having a wall plate, am I correct that looks like I want PSB strap with restraint hanger?

That setup is to provide lateral restraint and support for a floor. The detail for resisting wind lift of the roof is on page one

 

[Ali2487]

Thanks again for your response. Considering my design does not include a wall plate, I think I have narrowed it down to two options, Hurricane Ties or Twisted straps with firrings to help create the run.

Is there any reason I should consider fitting wall plate or should it be fine to just be rested directly on top of the wall with ties / twisted straps to secure to the wall?

 

[Mr Chibs]

Thanks again for your response. Considering my design does not include a wall plate, I think I have narrowed it down to two options, Hurricane Ties or Twisted straps with firrings to help create the run.

Is there any reason I should consider fitting wall plate or should it be fine to just be rested directly on top of the wall with ties / twisted straps to secure to the wall?

Like these?

Wind Ties

Just saying, with a wall plate installed you will need a deeper fascia board.

 

[Ali2487]

Hi @Mr Chibs yes that's exactly what I had in mind to help me secure the roof down to the wall and prevent it from blowing away!

By no means a pro and this is my first full roof I'll be doing so just after but of advice. Thanks for your response

 

[Ali2487]

Quick update - outbuilding is up and ready to roof. Materials are being delivered tomorrow so I shall be making a start on that tomorrow

Just one thing I wanted to double check, I noticed that the builder used concrete fenline blocks under the dpc, bit surprised there as usually anything under dpc (to my understanding) should be engineering brick.

Is there a way to seal / render the concrete block below dpc to concrete foundation level?