# Forum Home Renovation Doors, Windows, Architraves & Skirts  What do I use to replace rotten wood??

## aaronjthompson

I have some windows where the bottom left hand corner (inside) gives way when I push on the paint and it appears that the wood underneath has rotted away (nearly 50 year old house). 
Before I dig it all out - can I just use builder's bog and or putty to replace the rotten wood before painting? 
Obviously I will also need to look for any dampness issues that caused the problem in the first place as well.

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## phild01

A similar thread: http://www.renovateforum.com/f84/rot...advice-111590/ 
Maybe a picture would help.  My liking is to remove window and replace rotted section, like for like, if it is really bad.  Also sort out the flashing if it is a water issue.

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## justonething

You have to find out how water was getting there before doing any patching up. if water ingress hasn't stopped it will push out any filler that you use. The filler actually will make it worse by keeping the wood wet. It is likely that water went inside your window through dried up and cracked putty. So first stop the water from getting in. Then dig out all rotten timber and treat it either with a copper based wood treatment or my favourite - fisholene. Leave the whole thing til summer time to make sure it has thoroughly dried. I would use then epoxy mixed with saw dust as a filler.

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## OBBob

Presumably it's a reasonable size area once you cut it out. Ideally you'd do what Phild01 suggests ... but that may be a bit more work than you'd planned. You could use something like a multitool (that can do blind cuts) to cut a square out that encompasses the rot and a bit more. Then cut a new piece of timer to fit, glue it in, fill sand and coat.  
Builder's bog sort of works (at least short term) but in reality it can be quite painful to get a large amount to stay where you want and it's not much more difficult to put a real piece of timber in.

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## FrodoOne

> I have some windows where the bottom left hand corner (inside) gives way when I push on the paint and it appears that the wood underneath has rotted away (nearly 50 year old house). 
> Before I dig it all out - can I just use builder's bog and or putty to replace the rotten wood before painting? 
> Obviously I will also need to look for any dampness issues that caused the problem in the first place as well.

  I agree with the previous comments and the need to find the source of the dampness.  I would be surprised if the problem were only on the inside - have you checked the outside? 
I had a similar problem in a 20 year old house with a floor to (almost ) ceiling window which had rot in the outside sill - which was almost at the level of the slab.
The rot extended almost through the depth of the sill and into the room behind but, since it was rotting from the bottom upwards, had fortunately not yet become evident inside. 
The cause was wind driven rain entering at gaps in the cement mortar between the brick courses adjacent to the window and running down the window frame to the sill.  These gaps were first filled with a suitably coloured "Mortar Filler" before scraping out as much of the rot as possible, applying "Wood Hardener" to the remaining timber sill and allowing the timber to dry out (in Summer). 
The resultant gap in the surface of the sill was about 80*30 mm, with an unseen void behind. A piece of timber was cut to fit most of the visible gap and the space behind and around it filled with "Builders Bog", smoothed down and painted when set.

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## China

From your thread it appears as though nyou have as yet not investigated the cause, it may be termites and not rot

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## FrodoOne

> From your thread it appears as though nyou have as yet not investigated the cause, it may be termites and not rot

  If that comment is addressed to me it was DEFINITELY wet rot and NOT termites.  There is a significant difference in that termites leave hollow tunnels whereas, with this rot, virtually all of the material was still there but in a "rotten" state - in several senses of that word. 
The rot started from the SIDE of the sill where water was penetrating via the missing mortar between the courses above and it actually also affected the bottom 20 mm of that side panel.
Because of construction, painting etc. water reaching the underside of the wooden sill was trapped between the sill and the concrete underneath it.  During the reconstruction process I ensured that there is now a small gap between sill and concrete where it slopes downwards on the outside of the building to allow any water which may enter to escape. 
As was said by justonething
"You have to find out how water was getting there before doing any  patching up. if water ingress hasn't stopped it will push out any filler  that you use." 
In truth, I actually made a repair to this sill about 4 years earlier, but then merely scraped out the existing rot, used a wood hardener (actually, it was "Blue7", which is now banned) and replaced the part then rotten with "Builders Bog".  I made the mistake of NOT checking from where the water was coming, and so the problem continued.

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## TheHammer

Skip the builders bog which is rebadged auto bog. They are all polyester resin. The stuff used in fibreglass boats. It sticks really well to steel and fibreglass. Not so good to wood. We only use it for filling minor defects like screw holes or some bad spots in trim. The proper product to use for permanent repairs on wood like window sills is epoxy resin. Use the straight resin for sealing up the old wood. Then mix some filler into it to make your own bog.

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## Random Username

What he said - epoxy is the go.  Have a look at the "WotRot" kits - DRIVE Marine Services

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## GraderL

My house is 40 years old and has no eaves.  I have had a problem with rotting window frames for over 20 years. 
Original treatment was with "Blue7" and filling with Builders Bog.  Over time the Builders Bog pulls away from the timber (or shrinks) and water gets into the crack rotting the timber next to the repair. 
Current repair method is as follows: 
1.  Earls Wood Hardener - Liquid Wood Glue
Where timber is rotted drill a series of holes as recommended and recover timber by using a syringe to squirt wood hardener into the holes.
Where timber is split, strip the paint and apply wood hardener to glue the fine cracks together.
Apply wood hardener to all rotted or aged timber surfaces before repair with filler to provide a secure surface for the filler to adhere to.
  A syringe allows wood hardener to be squirted inside rotted voids, and can be used for recovery of dried putty sealant around windows where paint has pulled away from the glass. 
2.  Selleys Liquid Nails Waterproof - Polyurethane Construction Adhesive
This product is excellent for window repairs as there is no mixing, turps clean up, and it sets as a solid material which can be sanded and removed with a chisel. It has excellent adhesion and still has some flex for movement.
 Setting is slow, particularly for deep filling so do these areas first.  Insert the nozzle right in to fill the void.
It expands slightly as it sets. The outer skin sets first, and the expansion drives adhesive into all adjacent openings and cracks giving an excellent result.  Sand or chisel excess when set.
Apply with a plastic blade to fill cracks in timber and surface defects. 
Good luck with your repairs.

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## Gregei

I would say simply remove the rotten wood and then coat that area using wood hardener. Then take the polyester filler and fix it using putty knife.

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## GraderL

Here is an example of repair using the technique that I have stated above.  The corner of this window is badly rotted with large voids in the timber.  It has been treated with Earls Wood Hardener using a brush and also syringed through the drilled holes to harden the timber and stop the rot.  Have a look at the video at https://www.youtube.com/watch?v=Jq5wlpKOmmc .
Selleys Liquid Nails Waterproof has then been used to fill the voids and to tie the window frame together.  This is working very well and the window frame is now quite strong.  It is literally being held together structurally by the adhesive which is also filling the gaps from the missing rotted timber.
Excess adhesive has been cut off at the drill holes and you can see the fine bubbles that form in the adhesive as it expands and sets.
Note the fine crack in the window frame at bottom of picture where Builders Bog has been used in an earlier repair.  Water gets in and rots the wood next to the Builders Bog repair.  It appears to shrink over time resulting in further rot.
Obviously his window needs to be sanded back and painted, but there is a lot more to learn by seeing it with the adhesive exposed.

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