Boarding loft and raising the floor

[Dogz111]

Hi all,

First post, so please bear with me

I'm looking to board my loft to store boxes and general stuff you accumulate. I've read quite a few posts on this topic and propose to lay timber at 90 degrees to the original joists to raise the floor and then put T&G boarding on top to create the floor.

I've been up in the loft and looked at the joists which are only 35mm thick. I'm slightly concerned that this thickness of joist won't take the weight of the additional wood and flooring?

Am I being overly concerned? The house in a newish build c2012 if that helps.

Obviously don't want to do anything which is going to damage my ceilings!!

Thanks

Dave

 

[JohnD]

35mm thick, but how deep, and over what span?

Presumably they are trussed rafters in a "W" sort of shape?

 

[Dogz111]

100mm deep and yes they are in a trusted shape

Joist run from front to back and appear to be c30ft in length or 9.14m if my maths is right

Thanks

 

[JohnD]

that's very long.

Presumably they are supported on intermediate walls. How long is the longest unsupported span?

 

[Dogz111]

Thanks for coming back to me.

The longest unsupported span is c2.4m

Thanks

 

[JohnD]

then your timbers are quite reasonable for a loft. Screw the counterbattens to them. They will not increase the total floor strength, but they will spread the load and increase rigidity. If you use ply for the floor, and screw it down, you will increase rigidity even more. The bigger the sheets, the better. It will never be strong enough for a habitable room. Position anything heavy directly over one of the intermediate walls.

You might also consider rigid foam insulating boards. You can screw the deck down to the timbers through it.

 

[Dogz111]

Am I ok to use batons bigger than the original 35mm joists?

I was thinking of using 45mm C16 timber or is than an over kill?

Thanks for all your advice - its appreciated

 

[JohnD]

yes, you can, but the extra weight is undesirable. Try to span them so they take advantage of supporting walls.

Round my way, garden decking timbers are often at a good price.