Loft hatch

From DIYWiki

Installing a loft hatch

Cutting a joist

Loft floor joists are generally spaced too closely to leave space for a practically sized loft hatch, so one joist is cut away to give enough space for the hatch. This is done as so:

  1. check there isn't a major load sitting on only the joist to be cut, or 2 joists, such as a water header tank.
  2. screw temporary crosspieces as in diagram B
  3. cut the middle joist
  4. fit crosspieces as in diagram D


Diagrams

  • 1 = original loft floor joists
  • 2 = newly added timber, same size as joists
  • 3 = temporary pieces to hold the joists still during work
  • 4 = Lining to fit


1     1      1
1     1      1
1     1      1
1     1      1
1     1      1
1     1      1
1     1      1
1     1      1
1     1      1
1     1      1

A. Before


 1     1      1
3333333333333333
 1     1      1
 1     1      1
 1     1      1
 1     1      1
 1     1      1
 1     1      1
 1     1      1
 1     1      1
3333333333333333
 1     1      1

B. Add temporary supporting cross pieces


 1     1      1
3333333333333333
 1     1      1
 1            1
 1            1
 1            1
 1            1
 1            1
 1            1
 1     1      1
3333333333333333
 1     1      1

C. Cut joist


 1     1      1
3333333333333333
 1     1      1
 12222222222221
 1            1
 1            1
 1            1
 1            1
 1            1
 12222222222221
 1     1      1
3333333333333333
 1     1      1

D. Add crosspieces


1     1      1
1     1      1
1     1      1
12222222222221
1            1
1            1
1            1
1            1
1            1
12222222222221
1     1      1
1     1      1
1     1      1

E. Remove temporary bracing


1     1      1
1     1      1
1     1      1
12222222222221
14444444444441
14          41
14          41
14          41
14444444444441
12222222222221
1     1      1
1     1      1
1     1      1

F. Add Lining

Job done.

How its done

Temporarily support the joist that will be cut. This can be done by laying 2x4 down flat over 3 joists, and putting a long screw or 2 in at each point. Its possible to omit this support, but not recommended, the ceiling is likely to break up from the sawing etc.

Make the 2 saw cuts in the joist.

Now 2 lengths of joist sized timber are fitted across to support the 2 ends of the cut joist. (If the ceiling is lath & plaster you'll need to use timber slightly shallower than existing joists.) These also act as 2 sides of the loft hatch hole. 2x 4" nails at each point will do the job, total 12 nails. Large screws are also an option, a bit more work but less ceiling damage likely. If you have big 2x8 timbers spanning a large distance, 3 nails at each point would be better.

Fit lining timber round the interior of the hole. 0.5-1" thick planed timber is good. Line the bottom of it up with the level of the ceiling.

Fit timber moulding to the underneath surface where the lining meets the plasterboard, mitring the corners.


Tips

Its good to have headroom above the hatch.

A loft hatch can be made long and thin if preferred, so that 4x8 sheets can go up.

Sheet the landing and close the bedroom doors, it'll be very messy. If its an old L&P ceiling, expect some severe filth to come down.

The loft ladder, if fitted, is best screwed through the lining and into the joists.

You'll need filler or plaster to make good ceiling damage around the hatch.

Joist hangers are also an option to support the new crosspieces.

Take care to get the hatch properly square, it makes life easier.

Don't forget to insulate the hatch itself, and to trim the insulation slightly at the opening edge so it opens ok. Draught excluder is also well worth having.

Another variation is to make the frame out of 2x4, hang the hatch/door on it, then fit the whole thing to the surrounding joists. This is a good option if you're fitting a ready made insulating loft hatch set.

Melamine coated chipboard makes a good general purpose loft hatch, as long as you have the equipment to cut it clean & square. Lateral tensile strength is weak in chip, so longish screws in pilot holes are best. Other sheet materials also work, such as blockboard, timberboard, or a firmly glued ply.


Insulation

Insulate the hatch topside with something soft and easily squashed, so the insulation doesn't get in the way.


See also