Carpentry advice needed: fitting risers to rafters

I’m considering redoing the insulation in my loft. The new standard depth is 10". My rafters are about 4". But my loft is my storage area. So I’ll need to remove all the floorboards and fit 6" risers on the rafters, right?

How do I best - and cheaply - do this? My first thought was to countersink screws. But it’s a very tight working environment with poor light - very easy to err. Could I simply use glue? Can you get brackets shaped like an H?

I’m also concerned about the amount of timber that I’ll need - or rather the price thereof. Any tips on where to source cheaper timber would be most welcome.

Or, could I really save on timber and use a combination of posts and less-thick runners?

Is this blown or batt insulation?

It will be some fibrous material.

When you say rafters do you mean the roof in addition to the attic floor joists? Do you have an open A frame attic or is it a truss system?

If you’re just raising the floor then I would pre-drill the boards you’re going to mount and use a right angle drill with a screw driver bit to screw them in. go to Harbor freight and buy a cheap one. You’ll still need to drill into the existing joists but having the holes started makes a big difference in tight places. I would also buy a hex driver headfor the drill and then buy hex drill bits so you can swap the drill bit and screw driver bit quickly. Make sure the drill bits are long enough for the job.

Do a parallel row at a time because it will be tough crawling back to the edge of the roofline.

My above suggestion was based on screwing a 10" board into the side of the 4" board. To stack them as you suggested would require a 10" spacer at a 90 deg angle and I don’t know if I would do that. [Here](When you say rafters do you mean the roof in addition to the attic floor joists? Do you have an open A frame attic or is it a truss system?)are some of the clips available.

Truss connector plate

It’s an A frame attic, i think, and for rafters read joists. I was thinking of putting the timber directly on top of the joists, not at right-angles, to make fitting the insulation straightforward.

I suspect that your joists aren’t adequately sized, at least as per the current codes. Run the extra lumber at right angles to the existing joists, so that they work as strongbacks. Personally, I’d just run 5/16" lag bolts through the intersections instead of running the 2X4 nailers since I don’t think that there will be that much horizontal load.

I’m not sure where the Land of Hope & Glory is or how your house is built, but you might also be able to install insulation between the rafters instead. This will cool the attic, giving the original insulation less of a temperature gradient to work across.

Strongbacks look rather simpler - and cheaper. Could I use angle brackets where the timbers cross?

You have considered loading, right. (?) Your “joists” are functioning as collar ties if it is an A-frame, and overloading is not a good thing here.
OK, so you have that under control. Look into “Larsen truss” to accomplish your aims, which could add some structural value. They are typically used as walls (vertical vs. horizontal) but being light weight and economical of material sound right up your alley.

Just wanted to recommend you consult local building codes if you havent already. Contacting the municipality is probably a good start. Insulating techniques vary considerably depending on climate, and certain practices could result in moisture damage if not suited to your location. Be sure you are not restricting airflow to the soffits!

Definitely recommend running your secondary joists perpendicular to the existing ones; easier to fasten, structurally superior, less prone to squeaking. If you are at all competent with tools, I would just toenail them in with a framing gun, (ear and eye protection!), 3 or 3 1/4" spikes should work fine. Be mindful you don’t shoot a nail through the ceiling. Alternate sides for each joint.

If you do not feel safe with air tools you could use screws, but it will take three times as long with more chance of splitting (unless you predrill, but that will take even longer).

Blown in insulation will be easiest (you can rent a machine) but batts will work too, just install the batts for the existing joists before installing the new joists.

Another question, how big is your access? Are you going to be able to get sheathing up there? Reasonably sized lumber?

Is giving up the storage space an option? If that is the case just blow insulation up there and forget all the extra carpentry , because it sounds like no small job.

I wouldn’t. You will get a lot better of connection if you lag everything together. Also, lag bolts will be a lot cheaper than angle brackets and nails.

I’m not sure how you would lag bolt a 90 degree crossover of joists. They make plates called hurricane clips that do what you’re asking. You could do the same thing with 6" of scrapwood. I’d still put wood spacers between the joists to make them rigid.

It’s easy to lag the joists together; just drill through the edge of the strongback with a long bit, then drive the screw with a ratchet or a speed handle. I would lube the lag bolt with wax to make it easier to drive and give you a better idea of when the bolt is seated (Personally, I use either beeswax or a new wax toilet gasket.) A 5/16" or 3/8" bolt is far less than one-third of the thickness of a 2X board and will not cause it to fail.

I’m not sure what hurricane clips would gain in this application. Lags give equivalent strength to the clips. Depending on how they are installed, the clips may not give as rigid of joint, and clips require many more fasteners, slowing the installation.

I’m not a big fan of lag bolts into the edge of boards but it would technically be ok and definately much faster. A half inch drill would certainly drive it in with no problem. I’d spray the bolts with Pledge to speed it up.

Thanks guys. I’ve now got good info with which to go to the timber merchants.