Holding down

[trialuser]

Hi, occasional lurker, now after a bit of preliminary  info please.

How is the timber frame (140mm) held down to the  foundations if there is no external skin of masonry, ie timber or steel cladding?

All the details I have been able to find show stainless holding down straps fixed to the frame uprights and built into the external skin of full height masonry.

 

Other products I have seen (https://www.strongtie.co.uk/products/detail/hold-down/81) seem to rely on being bolted into the concrete block foundations and I always thought mortar joints were fairly useless in tension. Is it enough to fix to the blockwork, or is a connection to the mass of foundation concrete required?

What have other people used when constructing lightweight clad external wall.

The soleplate will be shotfired into the blocks, the frame nailed to the soleplate, but what is the correct way to provide restraint against any uplift force to the whole lot?

I hope that makes sense, thanks

Sid

Edited December 23, 2019 by trialuser

[andyscotland]

My engineer specified:

 

Quote

TF-5. HOLDING-DOWN STRAPS
 a. L-shaped anchor straps for perimeter stud walls to be minimum of 30 x 1.5mm thick steel straps, 
nominal 100mm long horizontal leg
 b. Fix short horizontal leg to concrete slab with M8 x min 85mm long Thunderbolt or equal with washer. 
 c. Nail vertical leg to studs, minimum 5no. fixings, top one not less that 150mm from top of strap; 
fixings per manufacturer’s specification.

 

This is for an extension sitting on a raft slab/foundation with thickened edges, the walls sit on a concrete kerb cast in situ on top of the slab. The L straps just go dowm and bolt into the slab. Two sides of the extension are joined to existing masonry building.

 

Not sure if this would be adequate for a freestanding structure on traditional foundations. But I would think ultimately if you can get a secure fixing down into a mass of concrete below/beside the wall it's unlikely to go anywhere.

[nod]

While the sole plate is anchored down the sheer weight of the structure will hold it in place 

Pretty much like the roof straps holing a roof in place 

On site work theses are often fixed to the wall plate  it not attached to the block work 

 

 

[Russell griffiths]

What you need to consider is where you live, the timber frame house I built in Australia was held down by large threaded rods that went from the roof to the foundation, these are known as cyclone straps. 

Over in good ol sunny England cyclones are a rare thing so wind uplift is not really required, so a simply system like the two listed is all that is required. 

 

You should check with building control though though to see what they like. 

[Russell griffiths]

Omg 

as im sitting here bored I thought I would google RESTRAINT STRAPS well that turned up a few images I hadn’t thought I would see at 7.30 in the morning. ??

[Ferdinand]

12 hours ago, trialuser said:

Other products I have seen (https://www.strongtie.co.uk/products/detail/hold-down/81) seem to rely on being bolted into the concrete block foundations and I always thought mortar joints were fairly useless in tension.

 

I think a reinforced slab, which is what these connect to (I think), is also good in tension - and is very dissimilar to a 'mortar joint'.

[Mr Punter]

They often use sole plate anchors which are nailed to the inside of the sole plate and then shot fired into the slab.

 

https://www.wickes.co.uk/Wickes-Sole-Plate-Anchor-50mm-SPA50/p/214975

[Thedreamer]

15 hours ago, trialuser said:

Hi, occasional lurker, now after a bit of preliminary  info please.

How is the timber frame (140mm) held down to the  foundations if there is no external skin of masonry, ie timber or steel cladding?

All the details I have been able to find show stainless holding down straps fixed to the frame uprights and built into the external skin of full height masonry.

 

Other products I have seen (https://www.strongtie.co.uk/products/detail/hold-down/81) seem to rely on being bolted into the concrete block foundations and I always thought mortar joints were fairly useless in tension. Is it enough to fix to the blockwork, or is a connection to the mass of foundation concrete required?

What have other people used when constructing lightweight clad external wall.

The soleplate will be shotfired into the blocks, the frame nailed to the soleplate, but what is the correct way to provide restraint against any uplift force to the whole lot?

I hope that makes sense, thanks

Sid

 

We have L shaped restraint straps that go under the blockwork to connect to the substructure of the house. 

 

https://www.strongtie.co.uk/products/detail/restraint-strap/333

 

Soleplate connected to blockwork using rawl plugs. 

 

Don't know what your putting on your roof, but with us, once a few pallet of slates were on the house, visually it felt pretty secure.

 

I'm building in the Hebrides (in a sheltered spot) but can still get weeks of windy winds. 

 

Edited December 24, 2019 by Thedreamer

[trialuser]

Thank you everyone, have a good christmas.

Roof will be tata cc urban hopefully, so not overly heavy, build will be at 100M 3 miles inland from coast, dumfries and Galloway, so reasonably windy at times. Plans show the strongtie brackets bolted through the soleplate into the blockwork, but that was my concern. I was thinking of also casting some of the L straps under the reinforced slab up against the inside of the blockwork, but potentially a bit fiddly ensuring they are in the correct place to coincide with upright studs.

Sid