[[Image:betterhomesgardens-707922405-1164323028.jpg]]How to cut out the rot in your weatherboard house.
Weatherboard houses have an appeal that can't be matched by brick. Timber boards just need a bit of regular maintenance to avoid fungal attack. If your home hasn't been loved as it deserves, you can replace weatherboards yourself - it's not difficult and can save you a fortune.
What you will need
Note: Purchase all quantities to suit the size of your repair job.
Framing timber to match existing say 100 x 50mm oregon
Aluminium foil laminate
Alcor damp-proof course (dpc)
Splayed, checked and nosed weatherboards (90 x 19mm cypress pine gives 80mm coverage)
Corner stop, 66 x 30mm
19 x 19mm quad trim
Primer and acrylic top coats
Downpipes and astragals as necessary
[[Image:betterhomesgardens-46124242-1164323030.jpg]]Check the extent of rot by prodding with a screwdriver; rotted wood is soft and easy to penetrate with a screwdriver blade. Remove any obstructions, such as downpipes, for access to corners where rot is most likely to occur. Mark extent of rot on each board with a permanent marker. Remove vertical corner stop.
To reveal rot in corner framing timber, draw a vertical line about 600mm from corner, set a power saw to cut to a depth a fraction of a millimetre less than the thickness of the weatherboard, then saw along the line without risk of cutting through electrical wires. Remove any trim under windows, then snap weatherboards away from the corner.
Check the condition of corner studs and bottom plate with a screwdriver.
Rot occurs when water enters from a damaged downpipe and travels down the corner window post, through the sill and into the framework. Rot occurs at the bottom of frames where water collects. Higher up the frame can dry out after rain.
[[Image:betterhomesgardens-380835004-1164323031.jpg]]Remove all the weatherboards from the corner back to where they join adjacent boards. Staggered butt joints look better than having all the joints in line.
Use a pinch bar and hammer to lever them off, being careful not to break the boards. Longer lengths can have the rotted ends cut off and the sound portions reused where shorter boards are needed.
Note the sizes of replacement framing. Bottom plates can be joined in length but the studs are best replaced entirely. Prime board all over to protect timber against cupping and rot. Store extra boards flat in a dry place.
[[Image:betterhomesgardens-23171905-1164323032.jpg]]Before removing rotted framing, make sure the roof is supported. Remove the rotted corner stud and section of plate underneath, then hammer in a timber corner prop to support the corner post above. Cut away the rotten section of frame that stops short of the corner, build a replacement section and fix in position. Once the new section supports the corner, the timber prop and the rotted frame on the other side of the corner can be replaced with new timbers. All frames must be a tight fit. You can also hire adjustable props to support the top plate or sill plate under a window. In some cases, external and internal props with a beam through the wall may be needed.
To protect the wall behind the weatherboards and to provide reflective insulation, line the frame with new aluminium foil laminate. Where the framing sits back from the edge of a concrete slab, shape Alcor dpc to suit the step and fit up behind the foil so any moisture which may flow down the foil will not sit on the concrete. Also, fold a strip of dpc around the corner as added protection against the weather.
[[Image:betterhomesgardens-424458341-1164323033.jpg]]Cut a timber block to fill any notched section of sill. Set the block in place with plenty of epoxy adhesive to fill the gap and provide waterproofing. When epoxy is dry, use a plane, then a sanding disc on an angle grinder to shape block to suit the sill profile.
Run a taut row level stringline along bottom row of weatherboards. At two or three points along the line, measure up to the window sill or existing boards and note any difference in height. If necessary, adjust weatherboards by fanning out where height is greater.
Temporarily nail a 66 x 30mm batten to the corner with a 25mm overhang. This will act as a stop for the weatherboards and form a neat vertical edge. Measure and cut each weatherboard individually, starting with the bottom board. Undercut the boards slightly, which means cutting at a very slight angle towards the back of the board. This allows very tight butt joints to be made. Before fitting, give the end grain a good coat of primer as added protection against rot.
[[Image:betterhomesgardens-828345091-1164323035.jpg]]Nail on the boards, sighting along the wall and referring to the stringline to ensure they are straight. Keep an eye on the measurement to the top of the wall as you work upward. Predrill for the nails at board ends to avoid splitting. When all the boards are on one side of the corner, fix them to the other side in the same way.
Remove the temporary corner batten and replace it with a preprimed corner stop nailed to the studs. Add the trim under the window sill.
Paint with two coats of quality acrylic paint. Add the replacement downpipe, having ordered it to suit the eaves overhang and wall stand-off; use blocks so it clears the sill. Fix to wall using new astragals spaced at 1200mm centres.
TIP: Matching weatherboards
Old weatherboards can be hard to match. Take a sample to a large timber yard as many have milling machines that can reproduce older profiles. The average set-up fee is about $100 so while you are at it have some extra lengths milled for future use.
Source: Better Homes and Gardens, August 2000