Browse Forums Building A New House 1 Jan 24, 2024 1:33 pm I believe I joists are cheaper is it worth sticking with I joists rather then avoiding possi trusses or upgrading an I joists chord to 90mm as apposed to 45mm I realise posi trusses can be upgraded to lvl timber to, noise concern, thumping and vibration is an issue in comparison to possible, is it the cheap feel nature. House would be an investment property Thank you Re: Cost differences between I joists vs posi trusses and is 3Feb 05, 2024 12:01 pm If you’re concerned about noise it won’t matter what you use for joists. You need to increase the density of the floor system to improve the sound rating or change the ability of the floor to bend/move under load - or both. There are various bulk insulation products and acoustic rated products that will sort the noise out. You could even look at updated the flooring substrate to something thicker or denser, although im not sure if the change would be noticed. The extra weight would have to considered in the live load calculations for the flooring system design. Personally I’ve had the same issues with LVL and posi joists with creaks. The main thing is how the flooring is fixed. Screws and adhesive is way better for holding the following in tension as the materials dry out over time (further dry out) - than nails and adhesive. Nails have better bending strength than screws which better shear strength (until they fail). As timber dries it moves/shrinks etc and those gaps create squeaks. Having a wider web on the top is only increasing the ability of the member to transfer load. But that really doesn’t do much in residential unless it’s for transferring loads applications. If you wanted to reduce the potential for vibration the spans of the post truss need to be reduced so there is less flex or ability to bend (fractionally bend). This would mean the addition of lower support walls or posts to support floor joists. Here is an extract from the post installation design guide on this: “Where PosiStruts® are near their maximum span for large open areas like rumpus rooms and family rooms, or where additional floor stiffness is required the maximum spans given in Tables 1 to 8 should be reduced by 10%.” Read it here - https://www.aaatrussesandwindows.com.au ... elines.pdf The good thing about posis is running services through them. It’s much easier. I’ve seen plenty of LVLs over cut or not drilled in accordance with AS1684. It’s pretty hard to bugger up a posi unless a web is cut. If you’re installing carpet upstairs you can always upgrade your underlay. If your timber flooring you can also out in a sound rated underlay to absorb impact. There are a heap of ways to reduce sound transmittance through flooring. I personally think your money is better spent on insulation or acoustic treatments rather than changing posis to LVL. My two cents Re: Cost differences between I joists vs posi trusses and is 4Feb 11, 2024 11:35 am obiwon If you’re concerned about noise it won’t matter what you use for joists. You need to increase the density of the floor system to improve the sound rating or change the ability of the floor to bend/move under load - or both. There are various bulk insulation products and acoustic rated products that will sort the noise out. You could even look at updated the flooring substrate to something thicker or denser, although im not sure if the change would be noticed. The extra weight would have to considered in the live load calculations for the flooring system design. Personally I’ve had the same issues with LVL and posi joists with creaks. The main thing is how the flooring is fixed. Screws and adhesive is way better for holding the following in tension as the materials dry out over time (further dry out) - than nails and adhesive. Nails have better bending strength than screws which better shear strength (until they fail). As timber dries it moves/shrinks etc and those gaps create squeaks. Having a wider web on the top is only increasing the ability of the member to transfer load. But that really doesn’t do much in residential unless it’s for transferring loads applications. If you wanted to reduce the potential for vibration the spans of the post truss need to be reduced so there is less flex or ability to bend (fractionally bend). This would mean the addition of lower support walls or posts to support floor joists. Here is an extract from the post installation design guide on this: “Where PosiStruts® are near their maximum span for large open areas like rumpus rooms and family rooms, or where additional floor stiffness is required the maximum spans given in Tables 1 to 8 should be reduced by 10%.” Read it here - https://www.aaatrussesandwindows.com.au ... elines.pdf The good thing about posis is running services through them. It’s much easier. I’ve seen plenty of LVLs over cut or not drilled in accordance with AS1684. It’s pretty hard to bugger up a posi unless a web is cut. If you’re installing carpet upstairs you can always upgrade your underlay. If your timber flooring you can also out in a sound rated underlay to absorb impact. There are a heap of ways to reduce sound transmittance through flooring. I personally think your money is better spent on insulation or acoustic treatments rather than changing posis to LVL. My two cents ★★★★★ Yes the knot that missing and split on the end. Turns out it needs rectification. 6 3075 Hi All, about to commence a bathroom renovation and need some advice on subfloor works. Current subfloor is hardwood T&G floorboards on 90x45 joists, but intention is to… 0 6248 Thanks for all replies. I just noticed now the pictures I added to post right on top of page were wrong. I attached pictures showing "current" and my "suggested" floor… 9 15153 |